choice of designed ligands giving a broad range of structures. In MOFs, the ...... Al NMR spectra were recorded at 70.39 MHz and are reference to aqueous ...... Cl25. C27. C29. O31. -174.9(3). Cl44. C27. C29. O30. -111.7(4). Cl44. C27. C29.
[i]
[ii]
[iii]
Declaration
I hereby declare that the subject matter presented in this thesis entitled “Synthesis and Characterization of Some Modified Metal Alkoxides as Precursors for Metal Oxide Nanomaterials and Some Metal Organic Framework Compounds” is the results of experimental investigations carried out by me in the Department of Chemistry, Motilal Nehru National Institute of Technology, under the supervision of Dr. Ashutosh Pandey and it has not been submitted elsewhere for the award of any degree or diploma or membership, etc.
Signature of the candidate Dinesh Kumar Gupta (Reg. No. : 2007RCH03)
[iv]
Contents Acknowledgement Summary List of Publications Abbreviations
vii ix xiv xvi
Chapter-1 General Introduction
1-39
1.1 Metal organic framework compounds (MOFs) 1.1.2. Synthetic methods 1.1.2.1 Synthesis from solutions at normal pressures 1.1.2.2 Synthesis under hydrothermal conditions 1.1.2.2.1 Ionothermal synthesis 1.1.2.2.2 In situ ligand synthesis 1.1.3 Prediction of network geometry 1.1.3.1 Secondary building units 1.1.3.2 Effect of anion 1.1.4 Properties and Applications 1.1.4.1 Structural stability 1.1.4.2 Sorption and exchange of liquids and vapors 1.1.4.3 Luminescence properties 1.2 General introduction of metal alkoxides 1.2.1 Types of metal alkoxides 1.2.2 Oligomerization of alkoxide complexes [M(OR) n]x 1.2.3 Significance of metal alkoxide chemistry 1.2.4 Modified homometallic alkoxides 1.2.5 Heterometallic alkoxides 1.3 Metal/ mixed metal oxides nanomaterials 1.3.1 Mechanism of sol gel condensation with metal alkoxides 1.3.2 Advantages of sol-gel process References
[v]
2 3 3 4 7 9 11 15 16 17 17 18 19 21 22 23 24 25 28 30 30 31 33
Chapter-2 Metal Organic Frameworks (MOFs)
40-111
2.1 Synthesis and characterization of Na2(Pzta)2(H2O)2]n (1) 2.2 Synthesis and characterization of [Zn(Pzta)2(H2O)2] (2) 2.3 Synthesis and characterization of [Cd3(pzta)2(μ-Cl)4(H2O)2]n (3) 2.4 Synthesis and characterization of compound CoH4N4C3O3 (4) 2.5 Synthesis and characterization of compound CoH6N8C5O2 (5) 2.6 Synthesis and characterization of compound CoH4N6C4O2 (6) 2.7 Synthesis and characterization of compound CoH3N6C3.5O2 (7) 2.8 Synthesis and characterization of compound BaH4N4C3O3 (8) 2.9 Synthesis and characterization of compound BaH5N8C5.5O3 (9) 2.10 Synthesis and characterization of compound MnH6N8C5O2 (10) 2.11Synthesis and characterization of compound CoH4N10C6O (11) 2.12 Synthesis and characterization of compound SrH4N10C6O (12) 2.13 Synthesis and characterization of compound BaH4N10C6O (13) Experimental References
44 52 60 71 72 73 74 75 76 77 78 79 80 81 109
Chapter-3 Some modified alkoxides based on Al, Ca, Mg and their sol-gel derived metal/mixed metal oxides 112-173 3.1 Synthesis and characterization of carboxylic acid modified aluminum alkoxides 3.2 Synthesis and characterization of Aluminum acetylacetonates 3.3 Heterometallic alkoxides 3.4 Metal/ mixed metal oxides Experimental References
117 137 143 153 163 172
Chapter-4 Synthesis & Characterization of TiO2 films by Ti(OBun)4 modified precursors 4.1 Synthesis and characterization of Ti(OBun)2(OOCCHCl2)2 4.2 Synthesis and characterization of Ti(OBun)2(OOCCCl3)2 4.3 Influence of different precursor chemistry on TiO2 film morphology 4.4 Effect of deposition techniques Experimental References [vi]
and it’s 174-199 177 178 190 193 195 198
Acknowledgements I bow my head before that almighty and merciful god for giving me the courage and fortitude to complete this work. With profound regards and respect, I avail this opportunity to express my deep sense of gratitude to Dr. Ashutosh Pandey, Department of Chemistry, MNNIT Allahabad, for introducing the present research topic and for his inspiring guidance, constructive and valuable suggestions throughout my research work. It would have not been possible for me to bring out this thesis without his help and constant encouragement. I am also grateful to Dr. S. S. Narvi and Dr. N. D. Pandey whose vast knowledge in the field of science and technology has enlightened me in different areas of this experimental research work. Their deep sense of appreciation and dedication to research has been a constant source of inspiration to me. I would like to express my gratitude to all the faculty members, all research scholars and supportive staff of the Department for their cooperation, suggestions and encouragements in my research work. I would like to express my thanks to Ms. Sadhana Singh for her tremendous cooperation and also to Dr. Jay Singh, Dr. Santosh Kumar, Dr. Manish Srivastava, Dr. Brijesh Singh, Dr. Archana Singh, Dr. Bandana Singh, Dr. Mrigandra Dubey , Dr. Rakesh Mishra, Dr. Rucha Upadhyaya, Dr. Kafeel Ahmad, Dr. Shipra Tripathi, Dr. P. P. Singh, Dr. Manish Singh, Dr. Pramod Kumar, Mr. Rajesh Kumar, Mr. Digvijay, Dr. Nidhi Vyas, Dr. Rinki, Mrs. Ambuja, Mr. R. P. Singh, Ms. Kiran Gupta, Mr. G. Thiyagarajan, Ms Subia Ambreen, Md. Israr Ahmad, Ms. Nidhi Nigam, Mrs. Khushboo Tripathi, Mr. Dilip, Mrs. D. [vii]
Archana, Mr. Nitin Srivastava, Mr. Dharmendra Sahu, Mr Rajesh Kumar, Mr. Rajneesh K. Mishra, Mr. Aashish Jha, Md. Mahfooze, Mr. Dhananjay Tripathi, Mr. Rajesh Verma, Mrs. Arti, Md. Danish and my all friends for their useful discussion and kind help during my experimental work. I would like to acknowledge Department of Physics, MNNIT and Center of Biotechnology, University of Allahabad, Allahabad for granting the access of available research facilities. I am thankful to Prof. Dr. Em. H. Nöth and Dr. Peter Mayer, Department of Chemistry and Biochemistry, University of Munich, Germany for providing access to multinuclear NMR and the Single Crystal X-ray Crystallography. I am thankful to Dr. Stephane Daniele, MRSC, Université Claude Bernard-Lyon 1, France, for providing access to the Single Crystal X-ray Crystallography. I am thankful to Department of Chemistry, BHU and Ceramics Department, IT-BHU, Varanasi for providing access of available research facility. I would like to thanks my sister Mrs Kamal Lata Gupta, my brother in-law Dr. Samish Gupta and sweet Rani, Mayuri & Ayushi to give memorable joyful moments during my Ph.D. programme. I would like to thank my parents and other family members for their support for choices in all my life and their love, which has been a constant source of strength. I feel a deep sense of gratitude for my father Sri Late Ram Avatar Gupta Mahuley and mother Smt. Tulsa Devi Gupta who formed a part of my vision and taught me the good things that really matter in my life.
Dinesh Kumar Gupta [viii]
Summary The metal alkoxides are the class of compounds having general formula M(OR) z (R=Alkyl/aryl group) wherein Mδ+-Oδ--C bonds are polarized in the shown direction. The variation in the polarity of the bond depends upon the electronegativity of the central metal (M), consequently the nature of metal alkoxides varies from covalent monomers to electrovalent polymeric solids. The volatility and solubility in common organic solvents of certain metal alkoxides has made them attractive precursors for depositing pure metal oxides by chemical vapour deposition (MOCVD) or by the sol–gel process. The extreme hydrolytic instability of the alkoxides in the sol-gel process is currently being controlled by addition of complexing reagents or by partial hydrolysis to obtain new molecular precursors with different structures, reactivities and functionalities than the parent alkoxide. The process has eventually been called the ‘chemical modification’ of metal alkoxides. These modified metal alkoxides follow different pathway of sol gel polymerization than their parent alkoxides which has a significant effect in the resulting metal oxides. This has opened avenue for molecular engineering of the resulting building blocks during the sol gel process. The carboxylate ligand displays a bridging coordination mode, it thus acts as a clamp and keeps the metal centers together in the molecular species and facilitates the desired composition even in the multi component oxide. With a view to understand naively the relationship between the precursor and the ultimate oxide, Klemperer has introduction recently the concept of building blocks in the sol-gel polymerization. In order to ultimately understand the characteristics of alkoxy carboxylates, we decided to investigate some of the basic chemistry associated with. [ix]
Special group of porous coordination polymers consisting of metal ions linked together by organic bridging ligands are referred as metal organic frameworks (MOFs) .These coordination polymers are formed via a wide choice of metals and almost infinite choice of designed ligands giving a broad range of structures. In MOFs, the metal ions and ligands {called Primary Building Units (PBUs)} assemble together to form molecular structural units {called Secondary Building Units (SBUs)}. A number of SBUs further join together via covalent and noncovalent interactions to generate the MOF structures. MOFs are now used in several applications such as gas storage, gas purification, gas separation, catalysis, nonlinear optics, magnetism and also in biotechnology. Fascinated by the marvelous structures exhibited by the MOFs we were tempted to synthesize and structurally examine some of these compounds and the findings are given in the present work. The entire work has been divided into four chapters. In the first chapter, the basic introduction of metal organic frameworks (MOFs) including their synthetic methods, structural features and potential applications has been discussed in brief which is followed by an introduction on modified metal alkoxides and their role as precursors in the sol gel process. A brief survey of applications of the nanocrystalline metal oxides has also been included in this chapter. In the second chapter, the hydrothermal syntheses and characterizations of some metal organic framework compounds involving in situ generation of tetrazole ligands have been given. Some of the synthesized complexes have also been characterized by single crystal X-ray crystallography. A novel sodium-pyrazinyltetrazole {[Na2(pzta)2(H2O)2]n has [x]
been made by reacting NaN3, cyanopyrazine and AlCl3 under hydrothermal condition (Figure 1). N hydrothermal reaction
N N
NaN3 + AlCl3 CN
N
140°C
Na2 (H2O)2 N 2 N N N
Reaction scheme
Figure 1: Reaction scheme, molecule and framework structure of complex [Na2(pzta)2(H2O)2]n
By reacting sodium azide, cyanopyrazine and zinc acetate under hydrothermal condition the product [Zn(pzta)2(H2O)2]n has been obtained (Figure 2). N Zn(O2CCH3)2.2H2O
NaN3
CN
hydrothermal reaction
N
o
N
130 C
N
N C N Zn N N 2
Reaction scheme
Figure 2: Reaction scheme, molecule and framework structure of complex [Zn(pzta)2(H2O)2]n [xi]
H2O 2
CdCl2.2H2O upon reaction with sodium azide and cyanopyrazine under hydrothermal
condition
in
the
presence
of
H3PO4
gave
a
novel
complex
[Cd3(Pzta)2Cl4(H2O)2]n (Figure 3).
N CdCl2.2H2O
NaN3 N
CN
H3PO4,H2O 135oC,48h
N Cd3
N
NN NN
Cl4 H2O 2
2
Reaction scheme
Figure 3: Reaction scheme, molecular and framework structure of complex [Cd3(Pzta)2Cl4(H2O)2]n The third chapter deals with the syntheses and characterization of modified metal alkoxides of aluminum with monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichoroacetic acid (TCA), acetylacetone (acac), 3-chloroacetylacetone. The products have been characterized by elemental, alkoxy group analysis, IR and multinuclear NMR spectroscopy. Single crystal X-ray structure of the product aluminum tris-3choloroacetyleacetonate is also reported (Figure 4). In addition, some heterometallic alkoxides based on aluminum, lead, magnesium and calcium have been synthesized and characterized by IR, NMR and single crystal X- ray crystallography. The modified
[xii]
alkoxides and their parent compounds have been subjected to sol-gel process and the properties of the resulting oxides are also compared.
Figure 4: Molecular structure of aluminum tris 3-choloroacetylacetonate In the fourth chapter, titanium butoxide has been used in the preparation of thin films and characterized by XRD and SEM. Modification of titanium butoxide with trichloroacetic acid (TCA) in different molar ratios are characterized by elemental, alkoxy group analysis, IR, NMR X-ray crystallography. These modified metal alkoxides are followed by sol-gel process and the gel was used in the preparation of thin films and also characterized
by
XRD
and
SEM
and
compared.
One
of
the
product
{Ti6O4(OC4H9)8(OOCCCl3)8} (Figure 5) has been characterized by Single crystal X-ray crystallography. (a)
(b)
Figure 5: (a) Titanium-oxide molecular core (b) molecular structure of Ti6O4(OC4H9)8(OOCCCl3)8 [xiii]
List of Publications
1. “Hydrothermal Synthesis, Structure and Photoluminescent Property of a novel Sodium-pyrazinyltetrazole framework compound”, Dinesh K Gupta, Sadhana Singh, Peter Mayer, Ashutosh Pandey*, Inorganic Chemistry Communications 14 (2011) 1485–1488 2. “Synthesis & Characterization of TiO2 films by Ti(OBun)4 and it’s modified precursors”, Kiran Gupta, Sadhana Singh, Dinesh K Gupta, Stephane Daniele, Ashutosh Pandey* Under process of Publication. 3. “Synthesis & Characterization of tris 3- chloroacetyleacetonate Aluminium (III)”, Kiran Gupta, Dinesh K Gupta, Stephane Daniele, Ashutosh Pandey* Under process of Publication. 4. “A 3D cadmium (II) coordination framework involving in situ tetrazole ligand synthesis” Sadhana Singh, Dinesh K Gupta, H. Nöth and Ashutosh Pandey* Under process of Publication.
[xiv]
List of Research Conference / Seminar / Workshop
1. “An Efficient Synthesis of Biologically Active Pyrazine Linked Novel Hydrazones” G.Thiyagarajan, P.Nithya, Dinesh kumar Gupta, Ashutosh Pandey* “International Conference on Biologically Active Molecules (ICBAM-2012)” Gandhigarm University, Madurai, Tamil Nadu on 9-11 March 2012 2. “Golden Jubilee Conclave on Technology for Sustainable Development -2011”, during 19-20 Nov. 2011, Organized by Motilal Nehru National Institute of Technology, Allahabad, India. 3. “National Seminar on Science and Technology- Inclusive Innovation” during 5-6 Nov.2011, The Allahabad Chapter of Indian Science Congress Association Organized by Department of Chemistry, University of Allahabad, Allahabad. 4. “National Symposium-cum-Workshop on X-ray Crystallography” during 08-09 March 2010, at Department of Chemistry, Banaras Hindu University, Varanasi, India, Dinesh K Gupta, MNNIT, Allahabad. 5. “Synthesis and Characterization of Metal Oxides Nanomaterials using modified alkoxides as Precursor” Dinesh Kumar Gupta and Ashutosh Pandey* International Conference on Advanced Nanomaterials and Nanotechnology (ICANN-2009)” during 09-11 Dec. 2009, Organized by Center for Nanotechnology, IIT-Guwahati, India. 6. “Recycling Helps to Maintain Soil Fertility”, Dinesh Kumar Gupta, 7th Indian Agricultural Scientists & Framer’s Congress, 19-20 Feb., 2005 at Sardar Ballabh Bhai Patel University of Agriculture & Technology, Meerut, India Organized by Bioved Research & Communication Center, Allahabad, India.
[xv]
Abbreviations α β γ νs νas θ δ λ ⁰C Å Acac AMICl AmTRZ Bpdc Bpee BTC DCA DMF DMNB DNT DTA Etacac FTO FWHM HIN HOFc Hpca IR IRMOF MCA MOCVD MOF MT NCS NDC
Alpha Beta Gamma Symmetric vibration Asymmetric vibration Theta Chemical shift Wavelength Degree centigrade Angstrom Acetylacetone 1-amyl-3-methylimidazoliumchloride 3-amino-1,2,4-triazole 4,4’-biphenyldicarboxylate 1,2-bipyridylethene Benzentricarboxylic acid Dichloroacetic Acid Dimethyl Formamide 2,3-dimethyl-2,3-dinitrobutane 2,4-Dinitrotoluene Differential Thermal Analysis Heptan-3,5-dione Fluorine doped Tin Oxide Full Width Half Maximum Isonicotinic acid Formic acid Pyridine-4-carboxlic acid Infra Red Spectroscopy Isoreticular MOFs Monochloroacetic Acid Metal Organic Chemical Vapour Deposition Metal Organic Framework Methyl tetrazole Thiocyanate Naphthalene dicarboxylic acid [xvi]
NMR OBun OBut OMe OPri PBU Pc Pdip Pdon PEG PL PPO Pzta SBU SEM TCA TGA THF XRD YAG
Nuclear Magnetic Resonance Normal butoxy Tertiary butoxy Methoxy Isopropoxide Primary Building Unit Pyridine carboxylate 2-(4-pyridine)imidazo[4,5-f]1,10Phenanthroline 1,10-phenanthroline-5,6-dione Polyethylene glycol Photoluminescence 2-(2-pyridyl)-5-(4-pyridyl)-1,3,4Oxadiazole Pyrazinyltetrazole Secondary Building Unit Scanning Electron Microscopy Trichloroacetic Acid Thermal Gravimetric Analysis Tetra Hydro Furan X-ray diffraction Yttrium Aluminum Garnet
[xvii]
CHAPTER 1 INTRODUCTION
1.1 General introduction about Metal Organic Framework (MOF) compounds 1.2 General introduction about Metal Alkoxides and their role as precursors of Metal Oxide Nanomaterials
[1]
Chapter-1
1. Introduction 1.1 Metal organic framework compounds (MOFs) Special group of porous coordination polymers consisting of metal ions linked together by organic bridging ligands are referred as metal organic frameworks (MOFs). A supramolecular assembly or "supermolecule" is a well defined complex of molecules held together by covalent and noncovalent bonds. In MOF’s the coordinate bonds between metals and ligands are stronger than hydrogen bonds and they are more directional than other weak interactions. These coordination polymers are formed via wide choice of metals and almost infinite choice of designed ligands giving a broad range of structural, magnetic, electrical, optical, adsorptive and catalytic properties [1-2]. A huge range of network topologies can be designed by aggregating molecular building blocks to achieve a specific structure and morphology. MOFs are infinite one-, two- and three dimensional networks. The 2D and 3D structures of MOFs can exhibit small cavities or open channels. Large surface area, high porosity, structural regularity and fine tunability are among the well-known features of the MOFs. The porosity of these materials allows guest molecules to diffuse into the bulk structures with a broad choice of shape and size selectivity [3-4]. The most detailed structural information about MOFs has been obtained from single crystal X-ray crystallography. In fact, it is very difficult to interpret any of the observed properties in the absence of crystal structure. A number of metal ions and ligands {Primary Building Units (PBUs)} assemble together to form structural units called Secondary Building Units (SBUs). These SBUs further join together to generate the MOF structure. This is analogous to aluminosilicate zeolite chemistry wherein tetrahedral AlO 4 [2]
Chapter-1
and SiO4 secondary building units are made by Al, Si and O primary building units [5]. On the basis of the size of the pores MOFs are classified as microporous, mesoporous and macroporous. Solids with pore size of ≤ 2 nm are known as microporous while the mesoporous solids have range of 2 – 50 nm and the materials having pores above 50 nm are called macroporous. Based on the above discussed porosity, MOFs were firstly used for gas storage application. However, now several other applications such as gas purification, gas separation, catalysis, nonlinear optics, magnetism and biotechnological are also in practice. These critical applications have motivated the synthetic strategies of MOFs immensely [6-7].
1.1.2 Synthetic methods 1.1.2.1
Syntheses from solutions at normal pressures
For synthesis of MOFs the most common methods used are the room temperature solution method, refluxing solution method and hydrothermal reaction. In the normal solution method reactants mixed in a solvent are stirred, either at room temperature or under reflux leading to the generation of MOFs. For example, a MOF complex of cadmium, Diaquabis(4,4’-bipyridine N,N’-dioxide-κO)- bis(dicyanamido)cadmium(II) [8] was prepared by the reaction of Cd(NO3)2.4H2O and dicyanamide (dca) dissolved in methanol (20 mL) and water (1:1). After stirring the mixture for about 20 min, bpno (4,4’- bipyridine N,N’-dioxide) was added. The mixture was heated with continuous stirring for about 15 minuts. The colorless prismatic crystals of the complex (Figure 1) were grown from the solution by slow evaporation of solvent at room temperature over a
[3]
Chapter-1
period of several days. The molecular structure is extended to form a two dimensional layer structure involving weak hydrogen bonds {Figure 1(b)}. (a)
(b)
Figure 1: (a) Diaquabis(4,4’-bipyridine N,N’-dioxide-κO)bis(dicyanamido)cadmium(II); (b) molecular framework Another MOF of cobalt with molecular composition [Co(II)(NCS) 2(C9H10N2O)2] [9] was prepared by the reaction of cobalt(II) nitrate with (1-methyl-1H-benzimidazol-2-yl) and ammonium thiocyanate in water at about 333 K. Red platelets were separated from the solution after two weeks and the obtained molecular and framework structures are shown in figure 2. The structure is consolidated by hydrogen bonds between the organic ligand, thiocyanate anion and the uncoordinated methanol molecule, leading to a chain. (a)
(b)
Figure 2: (a) Ellipsoid plot of the [Co(II)(NCS)2(C9H10N2O)2] molecule; (b) Uncoordinated methanol molecule, leading to a one-dimensional chain
1.1.2.2 Syntheses under hydrothermal conditions In hydrothermal method the mixture of the reactants in water as solvent is sealed in an autoclave called hydrothermal reactor which is heated in a programmable oven. This [4]
Chapter-1
method favours the formation and crystallization of compounds at high vapour pressures. When other solvents are employed in place of water then the term solvothermal is used. Apart from than the pure hydro or solvothermal methods, mixtures of water and other solvents have also been employed to synthesize various MOFs. In comparison to the solution method, hydrothermal reactions play an important role in preparing robust and stable MOF compounds. This is due to increase in solubility of the reactants under hydrothermal conditions which make the reactions more likely to occur at lower temperatures than otherwise required. Further advantages of hydrothermal conditions are: (a) they take place in one step from the reactants (b) environment friendly and (c) sufficient growth for single crystals [10]. Different hydrothermal conditions facilitate the formation of different types of polymeric units through molecular building blocks. Even a small change in the reaction variables such as temperature, time, pH or the solvent type can influence the nature of the compounds. Hydrothermally
formed
MOF
of
cobalt
having
molecular
formula
[Co4(OABDC)2(OH)2(H2O)4]n. (H2O)4.4n complex [11] (Figure 3), {where (OABDC= 5oxyacetateisophthalate)}
has been made by the reaction of Co(NO3)2.6H2O , 5-
oxyacetate isophthalic acid and NaOH with 7 mL of H 2O placed together in a teflonlined stainless steel vessel. The vessel was sealed and heated at 160oC for 50 h. Then the reaction mixture was cooled at a rate of 10 oC h-1, leading to the formation of pink crystals. Polyhedral representation of the 2D layer connected by OABDC anions where pink, blue, orange, and green octahedrons represent Co1, Co2, Co3, and Co4 coordination environments, respectively are shown in figure 3(b).
[5]
Chapter-1
(a)
(b)
Figure 3 : (a) Molecular structure of [Co4(OABDC)2(OH)2(H2O)4]n. (H2O)4.4n ; (b) Extended framework pattern
In the hydrothermal synthesis of a mixed metal Zn/Cu coordination polymer [Zn3Cu2(IN)8] [12], a mixture of Cu(OAc)2 , Zn(OAc)2, HIN (isonicotinic acid), H3BO3 , HCl and H2O in the molar ratio of 2:10:20:3:3:500 was stirred for 10 min in the air to become a homogeneous solution (pH-2). Afterwards, this solution was sealed in a 25 mL teflon-lined autoclave and kept at 170oC for seven days. After being washed with deionized water and dried at room temperature for 24 h, the obtained orange crystals were examined by X-ray (Figure 4). The [Cu1Zn2(IN)9] structural building units are linked through bridging ligands IN to generate an open-framework with an unusual helical {Figure 12(b)}. (a)
(b)
Figure 4: (a) ORTEP of [Zn3Cu2(IN)8]; (b) 3D open framework
[6]
Chapter-1
1.1.2.2.1 Ionothermal syntheses In this method ionic liquids or eutectic mixtures are used as solvents. Ionic liquids are salts which generally consist of combinations of organic cations with either organic or inorganic anions. They are thermally stable, nonflammable and demonstrate very low vapor pressure. They have excellent solvating properties and high thermal stabilities. Another important feature of these ionic liquids is that they can act not only as solvent but also as structure directing agents. These ionic liquids can be recycled for further use making them economically viable. A eutectic mixture is a combination of two or more compounds which has a lower melting point than either of its constituents. Usually high vapour pressures are generated in solvothermal methods but the most fascinating feature of ionic liquids is that they possess a very low vapour pressure which in turn is safer than the solvothermal methods. For example, colourless crystals of a novel 2D MOF material [Cd2(AmTRZ)2.I3].(R4N+)] (Figure 5) (where AmTRZ = 3-amino-1,2,4-triazole and R4N+ = tetraethylammonium ) was obtained by the hydrothermal reaction of CdI2 and 3-amino-1,2,4-triazole-5carboxylic acid (AmTrz-COOH) and tetraethylammonium hydroxide (ionic liquid) at 170oC for 4 days [13]. In it’s structure, the two cadmium metal centers with different coordination environments create a molecular unit which is endowed with large helical porous channels around them. Furthermore, an unprecedentedly ordered extra-framework layer pattern of the encapsulated Et4N+ counter cations {Figure 5(b)} is also visible.
[7]
Chapter-1
(a)
(b)
Figure 5: (a) [Cd-I]n zig-zag chain; (b) along c-axis depicting helices formed around octahedral (green) and tetrahedral(yellow) centers.
In another reaction a novel magnesium metal-organic framework of magnesium [14] formulated as [Amim]2[Mg3(1,4-NDC)4(MeIm)2(H2O)2]·2H2O (Figure 6) was prepared by the reaction of Mg(NO3)2·6H2O (1 mmol) and 1,4-NDCH2(1,4-naphthalene dicarboxylic acid) (1 mmol)
in 1 mL AmimCl (1-propylene-3-methylimidazolium
chloride) in a sealed 20 mL teflon lined stainless-steel autoclave at 433 K for 6 days. Brown block crystals were obtained when reaction mixture was slowly cooled to room temperature. The structure of composed is constituted of linear trinuclear magnesium clusters and features of an anionic three-dimensional (3D) framework with 424·64 topology built upon 8-connected net. (a)
(b)
Figure 6: (a) Thermal degradation pathway of [Amim]Cl; (b) secondary building unit of MOF’s [8]
Chapter-1
The
similar
3D
mixed-ligand,
metal-organic
framework
[AMI][Ni3(BTC)2(OAc)(MI) [15] (Figure 7) was synthesized by reacting Ni(OAc)2 and H3BTC(1,3,5-benzentricarboxylic
acid)
in
[AMI]Cl
(1-amyl-3-
methylimidazoliumchloride). The framework is formed by connecting 2D planes, made up of 32- and 48-membered rings, through 1D chain which are composed of 32membered rings. (a)
(b)
Figure 7: (a) asymmetric unit; (b) 3D framework formed by the linkage of the 2D layers via 1D double chain.
1.1.2.2.2 In situ ligand syntheses Metal organic frameworks are usually obtained by using pre-designed linkers. These are either commercially available or synthesized prior to use. Recently, a new strategy has been developed by chemists in which ligands are synthesized under in situ hydrothermal conditions. In this approach, instead of pre-synthesized ligands, their precursors are used to generate MOFs. This method is of great interest in both organic as well as coordination chemistry for the preparation of coordination complexes, discovery of new reactions and [9]
Chapter-1
understanding their associated mechanisms. Recently, for example, in situ tetrazole ligand synthesis result in luminescent microporous cadmium-organic framework {[Cd(µ2-Cl)(µ4-5MT)]n [16] (Figure 8) by the reaction of CdCl2.2H2O with sodium azide, methyl cyanide and
pyridine-4-sulphonic acid wherein the ligand MT i.e. methyl
tetrazole has been generated by the cycloaddition (Scheme 1) of cyano and azide ions. H2O CdCl2.2H2O + NaN3 + pyridine-4-sulfonic acid + CH3CN
150 oC , 50 h
{[Cd(µ2-Cl)(µ4-5MT)]n
Scheme 1 (a)
(b)
Figure 8: (a) Unit molecule {[Cd(µ2-Cl)(µ4-5MT)]; (b) Microporous framework showing a large void. The copper complex [Cu3(μ2-OH)(pdon)3 (pca)(H2O)3][SiW12O40]·6H2O, (where (pdon=1,10-phenanthroline-5,6-dione, Hpca= pyridine-4-carboxlic acid) [17] (Figure 9) was
prepared by the reaction of Cu(NO3)2·4H2O, 4-pdip[2-(4-pyridine)imidazo[4,5-
f]1,10-phenanthroline] and H4SiW12O40·26H2O in 10 mL distilled water at room temperature followed by stirring for 30 min in air. The pH was adjusted to about 4.5 with 1 M NaOH and then the mixture was transferred and sealed in a 23 mL teflon reactor, which was heated at 160 °C for 3 days. After slow cooling to room temperature, green crystals of the complex were obtained. In this reaction both the liquids pdon and pca were generated under in-situ hydrothermal condition. [10]
Chapter-1
(a)
(b)
Figure 9: (a) In situ ligand transformation; (b) Molecular structure of Cu3(μ2OH)(pdon)3(pca)(H2O)3][SiW12O40]·6H2O Another example of in situ ligand generation is the formation of [Zn(2-pc)(4-pc)], (where pc- pyridine carboxylate ) [18] by the reaction of Zn(MeCO2)26H2O, 2-(2pyridyl)-5-(4-pyridyl)-1,3,4-oxadiazole (PPO) and CH3OH (Figure 10).
(a)
(b)
N O
N N
-
Zn+
O
O
Zn
-
O
(c)
O
N
CH3OH N
N
Figure10: (a) Reaction scheme; (b) Complex [Zn(2-pc)(4-pc)]; (c) 3D framework
1.1.3 Prediction of network geometry To make a coordination polymer or metal-organic framework a bridging ligand is reacted with a metal ion which have more than one vacant or labile site (labile- bond formation is reversible) [19]. Some of the possible modes are shown in figure 11.
[11]
Chapter-1
Figure11: The building block or modular principle for formation of coordination polymers. Since amorphous solid phase and gels have not been greatly investigated by single crystal X-ray crystallography therefore, to avoid amorphous MOF products, initially such metals and ligands are used which can form products which are capable to rearrange and give a thermodynamically favored product. Figure 12 (Wang, 2006) exhibits the coordination of metals and ligands as “Node-and-spacer” styles of various MOFs with their OD, 1D, 2D and 3D frameworks.
Figure 12: “Node-and-spacer” types of MOFs
[12]
Chapter-1
The commonly used labile metal ions such as Cu+, Cu++, Ag+, Cd++, Zn++, Co++, Ni++ etc. behave as nodes and ligands as spacers to give different kinds of MOFs. The potential problem with labile metal ions is that they do not impose a strong preference for geometry and therefore the possibility of predicting the structure of the generated network is very less. Another problem arises by the flexibility of the bridging ligands i.e. if the ligands have a number of possible conformations, then the framework geometry will be hard to predict [20]. For example, the ligand 1,2-bis (4-pyridyl)ethane, can adopt gauche or anti conformation in the compound (Figure 15) so the resulting framework geometry cannot be predicted with certainty. Anti
Gauche
Figure 13: Flexibility of the ligand 1,2-bis (4-pyridyl)ethane leading to two different complexes of Zn.
The three products (two of them shown in Figure 13) may differ in having ligands conformations as either all anti, anti-anti-gauche or gauche-gauche-anti. To overcome this problem some structurally rigid ligands, as shown in figure14, have been employed for the purpose while figure 15 shows the corresponding MOF patterns.
[13]
Chapter-1
Figure 14: Examples of rigid ligands used in the syntheses of coordination polymers
Figure 15: Various MOF patterns formed by the rigid ligands (1-15 of Figure 16). For clarity, interwoven networks and coordinated solvents are omitted. [14]
Chapter-1
1.1.3.1 Secondary building units In the structures of MOFs there are two main components: the organic linkers and the metal ions. In recent contributions, the concept of secondary building units (SBUs) has been applied with eminent success to the design of highly porous and rigid MOF structures. SBUs are helpful in determining the directionality for the construction of robust metal organic frameworks [21] (Figure 16) for example carboxylate MOFs.
Figure 16: Examples of SBUs from carboxylate MOFs. (a-i) O-red; N-green; C-black. In inorganic units metal-oxygen polyhedra are blue, and the polygon or polyhedron defined by carboxylate carbon atoms (SBUs) are red. In organic SBUs the polygons or polyhedrons to which linkers are attached are shown in green. The geometry for the complex i is an example of a tertiary building unit consisting of four SBUs (green triangles).
[15]
Chapter-1
Because of the steric requirements and rigidity the SBUs (made from a given node/linker combination) which dramatically reduces the number of possible network topologies, they become very important in construction of metal organic frameworks.
1.1.3.3 Effect of anion Anionic parts of the salts which are used in the syntheses of MOFs, may also play key roles in determining the polymeric structures, shapes and volumes in the crystal lattices. The different anions such as NO3-, BF6-, PF6 - , bis(4-pyridyl)tetrazine, etc. have different coordinating abilities to bridge between metal centers. Frameworks prepared with salts of AgO3SCF3 and AgBF4 exhibit three-dimensional (10, 3) nets (Figure 17), whereas use of AgPF6 and AgSbF6 produced two-dimensional (6, 3) (Figure 18) honeycomb nets [22].
Figure 17: X-ray structure of the 3D (10,3)-d net MOF-Co/AgBF4-1 (top) and the (10,3)-b net MOF-Fe/AgOTf-1 (bottom). Cobalt(III), iron (III), and silver(I) centers are represented by blue, gold, and gray polyhedral, respectively.
[16]
Chapter-1
Figure 18: X-ray structure of (6,3) nets in MOF-Co/AgPF6-1 (left) and in MOFCo/AgSbF6-1 (right).
1.1.4 Properties and Applications 1.1.4.1 Structural stability In zeolites Si-O and Al-O bonds are fairly strong and their breaking requires high energy. In comparison to zeolites, the weaker coordinate bonds in MOFs make them thermally unstable, which cause their decompositions at relatively lower temperatures. One of the main problems faced in the early stage of MOF chemistry was to preserve the structural stability after the removal of the guest molecules. However, the stability of MOFs can be enhanced by using hard-hard or soft-soft harmonizing between ligand and metal to maximize the bond strength. Crystalline structures containing pores in the size range of 1–2 nm and exhibiting thermal stability are highly desirable, especially if the pore system is more than one-dimensional. A major challenge facing in synthesis of the porous materials community is the development
of
tetrahedral
frameworks
containing
extra-large
pores
in
a
multidimensional network. Yaghi et al. have synthesized a series of isoreticular MOFs (IRMOF series) which show structural and thermal stability. For this purpose multidentate rigid ligands were incorporated in the system. TGA is the sole technique [17]
Chapter-1
used for the determination of the decomposition temperature with weight loss of the MOFs.
1.1.4.2 Sorption and exchange of liquids and vapors MOFs are highly porous materials with ability to absorb and exchange gases, vapours and liquids. When a single crystal was left open to the atmosphere, it apparently led to exchange of the nitromethane guests by the atmospheric water molecules. X-ray diffraction revealed that the product was however, still crystalline even though a change from a tetragonal to a cubic unit cell was accompanied with overall decrease in cell volume. Re-exposure to nitromethane caused regeneration of the original cell volume, although the cell remained cubic, and a second exposure to the atmosphere led again to the smaller cubic cell [23]. So far thousands of MOFs have been synthesized and structurally characterized; however, only a few hundred of them have been tested for their adsorption properties. Selective adsorption has been observed in less than about seventy MOFs, mostly based on gas adsorption isotherms. Similar to zeolites, in rigid MOFs, the adsorption selectivity may be related to the molecular sieving effect or on the different strengths of the adsorbate - adsorbate interactions. The structural analysis has revealed that manganese formate has a robust 3D framework structure with 1D channels [24] as shown in figure 19, which are connected to each other via a small window. Gas sorption experiments indicated that at 78 K this material selectively adsorbed H2 over N2 and Ar at 195 K and CO2 over CH4. In both cases, the adsorption capacities for the excluded gases N2, Ar, and CH4 were almost zero.
[18]
Chapter-1
Thus, the selectivity was attributed to the small aperture of the channels and size exclusion property. (a)
(b)
Figure 19: (a) Each octahedron represents Mn(II) cation coordinated by six formate ligands (b) Mn(II) centers are connected (red wire) to show the framework topology and zigzag open channels along the b-axis are shown as white surfaces with green entrances.
1.1.4.3 Luminescence properties In the MOFs, luminescence properties can be increase or decrease after the coordination of metal to ligand which makes them promising candidates for chemical sensing applications. MOFs of H2bpdc (bpdc = 4,4’-biphenyldicarboxylate and bpee (bpee = 1,2bipyridylethene) were chosen to build luminescent compounds for targeted biosensing applications due to their highly conjugated π-systems which could act both as the sources of luminescence and the chemical recognition elements (binding sites). [Zn2(bpdc)2(bpee)]·2DMF [25] contains roughly rectangular 1D channels in which DMF solvent molecules are encapsulated which can be removed either by heating under vacuum for an extended period of time or by evacuating at room temperature following solvent exchange with methanol and dichloromethane. Both treatments resulted in the same crystalline guest-free material. Guest-free was highly luminescent in the solid state at room temperature. The MOF appeared very bright to the eye when illuminated by a [19]
Chapter-1
UV lamp (at 254, 304, and 350 nm). It was confirmed that the emission peak wavelengths and intensity were independent of the excitation wavelength between 260 nm and 340 nm. The MOF were monitored, before and after exposing them to the equilibrated vapors of DNT (2,4-Dinitrotoluene) and DMNB (2,3-dimethyl-2,3dinitrobutane) for varied periods of time (10 s) at excitation wavelength 320 nm (Figure 20). There are obvious red-shifts of the fluorescence peak upon exposure to DNT and DMNB. (a)
(b)
Figure 20: Time-dependent fluorescence quenching of the corresponding fluorescence spectra before and after exposure to the analyte vapors of DNT and DMNB on excitation wavelength = 320 nm.
MOFs were also used in the various catalysis activities and servers as (a) opportunistic catalysis with metal nodes, (b) designed catalysis with framework nodes, (c) catalysis by homogeneous catalysts incorporated as framework struts, (d) catalysis by MOFencapsulated molecular species, (e) catalysis by metal-free organic struts or cavity modifiers and (f) catalysis by MOF-encapsulated clusters [26-30].
[20]
Chapter-1
1.2 General introduction of metal alkoxides and their potential applications The metal alkoxides are the class of compounds having general formula M(OR) z (R=Alkyl/aryl group) wherein Mδ+-Oδ--C bonds are polarized in the shown direction. The variation in the polarity of the bond depends upon the electronegativity of the central metal (M), consequently the nature of metal alkoxides varies from covalent monomers to electrovalent polymeric solids. Alkoxy ligands have a remarkable flexible bridging tendency between similar as well as dissimilar metal atoms, adjusting themselves according to the extent of ramification [31] of the alkyl groups and the atomic size of different bridging metal atoms. These features give rise to a number of interesting structures as shown in figure 22.
a
b
c
d
Figure 22: Some ORTEP of metal alkoxides (a) Al4(OPri)12, (b) Al2(OBut)6,U(OMe)6 and Sn(OBut)4 The chemistry of metal alkoxides has developed considerably in the fifties from the research group of Wardlaw. This area as a whole has seen an extraordinary spurt of activity [32] during the last three decades, due to a number of reasons, e.g. [21]
Chapter-1
Potential applications as precursors [33] for oxide based ceramic materials arising from their facile hydrolyzability, which can be controlled [34] by chelating ligands like carboxylates (acetic acid and its derivatives), βdiketones (acetyleacetone and its derivatives) etc,
These have been modified in various ways to generate new precursors with different structures and properties.
Possibilities of having excitingly novel structural building blocks [35].
Formation of oxoalkoxides either by hydrolysis [36] or by some side reactions [37].
The extraordinary stability of alkoxy bridges between dissimilar metals, which retain in many cases in their configuration during volatilization and hydrolysis [38] resulting in ultra homogeneous mixed metal oxide ceramic materials [39].
Catalytic activity is also a salient feature of these species [40].
1.2.1 Types of metal alkoxides The alkoxides having general formula [M(OR)x]n are known for most of s-,p-,d- and fblock elements. These may be divided into two types:
1. Homometallic Alkoxides: One type of metal atoms linked with one or more type of alkoxy ligands / groups.
2. Heterometallic Alkoxides: More than one type of metals linked with one or more type of alkoxy ligands / groups.
[22]
Chapter-1
Synthetic methods and properties of several metal alkoxides have been beautifully compiled in the book “Alkoxo and Aryloxo Derivatives of Metals” by D. C. Bradley and R. C. Mehrotra et al. [41].
1.2.2 Oligomerization of alkoxides [M(OR)n]x depends on a number of factors such as: 1. Electronic nature of the metal(loid) center : electron deficient metal centers favor the formation of high oligomerized species. 2. The size of metal(loid) atom : larger atoms tend to attain higher coordination number through intermolecular association involving alkoxide bridging. 3. The more sterically hindered alkoxides ligands would favor the less associated species, 4. The effect of electron withdrawing or donating substituents on the oxygen atom of alkoxides for instance electron withdrawing F atom reduces the electron density on the oxygen atom, making less prone to the formation of alkoxide [42] or aryloxo briding [43]. 5. The monomeric tricoordinated alkoxides of the type M(OR) X are coordinatively unsaturated and behave as Lewis acids. Therefore they accept a pair of electron if stericly favored either by neutral donor molecules or anions e.g. –OR or by intermolecular association to give tetrahedral, octahedral species or both. For example (1) boron tri isopropoxide, B(OPri)3 is monomeric with tricoordinate trigonal planer arrangement; (2) aluminium tri isopropoxide, Al(OPri)3 is dimeric in vapour state and shows trimeric nature when freshly distilled [44] and it becomes tetrameric solid when crystallized [45].
[23]
Chapter-1
1.2.3 Significance of metal alkoxide chemistry: Metal alkoxides are generally very reactive species due to the presence of electronegative alkoxy groups making the metal centers highly prone to nucleophilic attack. As a consequence of this, most of them are extremely sensitive to hydrolysis even by trace of moisture and require careful handling. Most of the metal alkoxides are readily soluble in non-polar solvents making them suitable candidates for future reactions. Their reactions with a large number of organic hydroxyl compounds such as alcohols, glycols, carboxylic acids, hydroxyl acids, β-diketones, silanols, schiff bases etc. with stepwise removal of the alkoxy group result into intermediate products stable enough to be isolated. Ebelman [46] was the first to show that sols can be obtained by hydrolysis of a product of reaction of silicon tetrachloride with ethanol and can be used to make fibers of amorphous gel as optical lenses. Significant work have been done on silicate sols and gels [47]. The chemical reactivity of the metal alkoxides strongly depend on their molecular structures. For example, oligomeric titanium alkoxides in which Ti has a higher coordination number are less reactive, allowing better control of the hydrolysis and condensation reactions. Therefore, monodispersed TiO2 particles are usually obtained from [Ti(OEt)4]3 rather than Ti(OPri)4 [48]. Also, as the oxidation state of the metal decreases (divalent metals give insoluble polymeric alkoxides [M(OR) 2]n where M = Fe , Co , Ni , Cu etc.). It was due to this reason that sol-gel synthesis of superconducting ceramics having high Tc (critical temperature) such as YBa2Cu3O7-8 [49] requires bulky ligands such as (2,2-diethoxide)ethoxide for soluble copper oxide molecular precursors.
[24]
Chapter-1
Apart from oligomerization, solvation is another factor which helps the metal in increasing its coordination number. X-ray diffraction studies on [Zr(OPr i)4PriOH]2 [50] and [Ce(OPri)4PriOH)]2 [51] show that alcohol molecules are directly bonded to the metal centers to increase it’s coordination number. Since coordination expansion occurs via alkoxide bridging or solvation, the molecule complexity of metal alkoxides can also be tailored by an appropriate choice of solvent. The extreme hydrolytic instability of the alkoxides is currently being controlled by adding complexing reagents or by partial hydrolysis to obtain new molecular precursors with different structure, reactivity and functionality. The process has eventually been called the ‘chemical modification’ of metal alkoxides.
1.2.4 Modified homometallic alkoxides The compound Zr4(O)2(OFc)2(OPri)10 [52] (Figure 23) has been made by the reaction of [Zr(µ-OPri)(OPri)3(H-OPri)]2, formic acid (H-O2CH or H-OFc) and ~10 mL of toluene. In the molecule four Zr atoms are tetrahedrally arranged around a µ4-O. Another oxide is present as µ-O linking two of the four Zr atoms. The remaining ligands asymmetrically arranged around this central core: four µ-OPri, six terminal OPri, and two µ-OFc ligands. Both OFc ligands bridge two Zr atoms.
Figure 23: ORTEP of Zr4(O)2(OFc)2(OPri)10 [25]
Chapter-1
The compound [Zr3(O)(OAc)5(OPri)5] (Figure 24) has been made by [Zr(µOPri)(OPri)3(H-OPri)]2, acetic acid (H-O2CCH3 or H-OAc) and ~10 mL of toluene, heated for 10 min. The molecule possesses a C2 center of symmetry with two Zr atoms adopting pentagonal bipyramidal (PBP) geometry whereas the Zr atom adopted an unique Octahedral geometry. The three Zr metal centers are surrounded by two µ-OPri and one µ-OAc ligands. Due to charge balance, one of these ligands must be an Pr iOH. An additional PriOH was also found in the unit cell.
Figure 24: ORTEP of Zr3(O)(OAc)5(OPri)5 Distorted octahedral geometry around Zr was found in compound [Zr2(OPc)2(OPri)6]2 (Figure 25), when it was made by [Zr(µ-OPri)(OPri)3(H-OPri)]2, isobutyric acid (HO2CCH(CH3)2 or H-OPc) and ~10 mL of toluene, heated for 10 min. The structure possesses a C2h symmetry where the two sub-moieties are linked by µ-OPc ligand. The smaller unit consist of two Zr metal centers bridged by two OPr i, one µ-OPc ligand, and two terminal OPri ligands. A solvated molecule formed.
Figure 25: ORTEP of [Zr2(OPc)2(OPri)6]2.HOPc [26]
Chapter-1
In the alkoxide modification, aluminium isopropoxide reacts with acetylacetone (acac) and 3,5-heptanedione (Etacac) to give [Al(OPri)2(acac)]3 and [Al(OPri)(Etacac)]2 their single crystals were reported respectively [53] (Figure 26).
(a)
(b)
Figure 26: (a) ORTEP of [Al(OPri)2(acac)]3; (b) ORTEP of [Al(OPri)(Etacac)]2 Recently, modification has been done by reacting Zr(OPri)4(PrOHi) with di- and trichloroacetic acid in 1:1 molar ratio in toluene. The products Zr2(µ-OiPr)2(µOOCCHCl2)(OPri)4(OOCCHCl2)(HOPri)
and
Zr2(µ-OiPr)2(µ-
OOCCCl3)(OiPr)4(OOCCCl3)(HOPri) [54] were formed respectively (Figure 27). (a)
(b)
Figure 27: (a) ORTEP of Zr2(OPri)6(OOCCHCl2)2 (HOPri); (b) ORTEP of Zr2(OPri)6(OOCCCl3)2(HOPri)
[27]
Chapter-1
1.2.5 Heterometallic alkoxides An attractive property of the alkoxides is their ability to form mixed metal species MM′(OR)z+x called hererometallic alkoxides. They may consist of two or three different metallic elements linked via alkoxo groups and / or oxo ligands of various bridging modes. Furthermore, the resultant heterometallic species have been found to be more soluble than their parent species. As stated earlier, the hydrolytic susceptibility of metal alkoxides has been successfully exploited in obtaining oxide based ceramic materials via sol-gel and MOCVD techniques. These have got wide application as multicomponent glasses [55], electronic materials [56], thin films [57], fibers in aerospace, automotive industries as well as in many every day applications that we use. The advantages of the sol-gel process over the conventional ceramic process reside in high purity of metal alkoxides precursors, the homogeneity of the components at molecular level and low processing temperature. The compound Co2Al2(OPri)6(acac)4 [58] (Figure 28) has been made by disolving Co(acac)2 and [Al(OPri)3]4 in toluene (2 mL) and subjected to the reflux for 10 min. In the molecule alkoxide bridges between the cobalt atoms are quite symmetric, while the bridges to the aluminum atoms are noticeably asymmetric, which provides an indirect indication of the more covalent bonding for these two bridging ligands.
Figure 28: Molecular structure of Co2Al2(OPri)6(acac)4
[28]
Chapter-1
The compound [Mg{Al(OBut)8}] [59] (Figure 29), two terminal ligands are present on each of the aluminium atoms. All the metal centers are present in a four-fold coordination of oxygen atoms. The angular distortions, due to the formation of four-membered Al(µOBut)2Mg rings, are reflected in the distorted tetrahedral geometries of Mg(II) and Al(III) centres. The compound [Mg{Al(OBut)8}] is used for formation of MgAl2O4 thin film by chemical vapor deposition.
Figure 29: ORTEP of [Mg{Al(OBut)8}] In addition the molecule [KTi(OPri)5]n, [60] (Figure 30) is linear one dimensional polymer and exhibits alternating five coordinate titanium moieties and tetrahedrally surrounded potassium atoms with respect to the coordination number of the metallic elements.
Figure 30: ORTEP of [KTi(OPri)5]n
[29]
Chapter-1
1.2.5 Metal/ mixed metal oxide nanomaterials The metal alkoxides have been used for wide range of applications such as catalysts for organic reactions or as precursors for forming metal oxide films, ceramic materials and glasses. The potentiality of their applications as “single-source” precursors for high purity heterometallic-oxide ceramic materials has been emphasized since 1980’s. The volatility and solubility in common organic solvents of certain metal alkoxides have made them attractive precursors for depositing pure metal oxides by chemical vapour deposition (MOCVD) or by the sol–gel process. The role of heterometallic oxides as useful materials in the electronics industry has stimulated research in this field in recent years leading to interest in the preparation and characterization of alkoxides of some of the pblock elements. 1.2.5.1 Mechanism of sol gel condensation with metal alkoxides --- M---OR + HOH --- M---OR + MOH M---O--M--O--M
M---OH + ROH M--O--M + ROH so on…….
Figure 31: Schematic representation of the sol-gel process for different applications [30]
Chapter-1
1.2.5.1.1 Advantages of sol-gel process •
Sol-gel process is usually a low temperature process, this means less energy consumption as well as less pollution.
•
Sol-gel process generates highly pure, well controlled ceramics. It competes with other processes like MOCVD / CVD and the derived ceramics are of much better quality.
•
In some cases sol-gel process can be a economical route, provided precursors are not very expensive.
•
Some benefits like getting exclusive materials such as aerogels, xerogels, zeolites, ordered porous solids by organic – inorganic hybridization are unique to sol-sel process.
•
It is also possible to synthesize nanoparticles, nanorods [61], nanotubes [62] etc using sol-gel technique.
•
Structural property relation in metal oxide nanomaterials by sol-gel process was first represented by Klemperer et al. [62(a)]. They observed that Si(OMe)4 on solgel gives SiO2 of 50 nm average particle size, Si(OMe)4 on controlled hydrolysis produced Si8O8(OMe)12, structure has been analyse by X-ray crystallogrphy, further on sol-gel process produced SiO2 of average particle size of 25 nm.
•
The sol–gel process is particularly useful for nonvolatile metal alkoxides which cannot be used in the MOCVD process where control of stoichiometry is important.
The binary metal oxides Al2O3, Y2O3, TiO2, V2O5, Nb2O5 and Ta2O5 have attracted considerable interest covering a wide range of applications.
[31]
Chapter-1
Nanocrystalline alumina (Al2O3) has been used for the fabrication of composite thick films which result in the reduction of residual stress and improvement in plasticity for integrated substrates [63]. Now a days significant applications of alumina in catalysis, bio-medical, electrotechnology, CD/DVD polishing, fabrication of superconducting devices, electronic and ceramic industry is been done. TiO2 has been widely used as a pigment and in sunscreens and also led to many promising applications in areas ranging from photovoltaics and photocatalysis to photoelectrochromics and sensors [64]. Titanium oxide (TiO2) of anatase phase has been studied extensively because of its promising photocatalytic performance. For example nanocrystalline TiO2 powders of anatase phase were obtained by the solvothermal route from the Ti(OR) 4 precursor precipitated in toluene under different concentrations. With decrease in particle size of TiO2 to the nanometer scale, the catalytic activity is enhanced because the optical band gap is widened due to the quantum size effect, combined with the increased surface area [65]. The sol–gel technique using metal alkoxides has been especially effective in producing ferroelectric, piezoelectric, and pyroelectric materials, e.g. BaTiO3 ; LiNbO3; LiTaO3; PbTiO3 ; Pb(Zr,Ti)O3(PZT); (Pb,La)(Zr,Ti)O3(PLZT); Pb(Fe,Nb)O3; and Pb(Mg,Nb)O3. Other superconducting materials such as YBa2Cu4 O8, yttrium aluminium oxides (YAlO3, Y4Al2O9 and Y3Al5O12-YAG) and aluminium zirconium oxide are also deposited by the sol–gel process by using corresponding metal alkoxide precursors. All these inorganic electronic materials prepared at low temperatures have stimulated enormous activities in the heterometallic oxide field.
[32]
Chapter-1
References [1]
Batten, S. R. and Robson, R., Angew. Chem. Int. Ed. 37 (1998) 1460
[2]
Keeffe, M. O., Peskov, M. A., Ramsden, S. J. and Yaghi, O. M., Acc. Chem. Res. 41(2008) 1782
[3]
Friedrichs, O. D., Keeffe, M. O, and Yaghi, O. M., Phys. Chem. Chem. Phys. 9 (2007) 1035
[4]
Hill, R. J., Long, D. L., Champness, N. R., Hubberstey, P. and Schröder, M., Acc. Chem. Res. 38 (2005) 337
[5] (a) Gottardi, G. and Galli, E., Natural Zeolites, Springer-Verlag, Berlin, (1985) (b) Ackley, M. W., Rege, S. U., Saxena, H., Microporous and Mesoporous Materials 61 (2003) 25 [6]
Czaja, Alexander U., Trukhan, Natalia and Müller, Ulrich, Chem. Soc. Rev.38 (2009) 1284
[7]
Murray, Leslie J., Dinca, Mircea and Long. Jeffrey R., Chem. Soc. Rev.38 (2009) 1294
[8]
Xu. Y., Yuan D., Xu Y., Bi. W., Zhou Y. and Hong M., Acta Cryst. E60(2004) m713.
[9]
Zhou Y.-Ling, Liang Hong and Hua Zeng M.H, Acta Cryst. E66 (2010) m189
[10]
Zhang, X. M., Coord. Chem. Rev. 249 (2005) 1201
[11]
Wang G-H, Lei Y-Q, Wang N., He R-L, Jia H-Q, Hu N-H and Xu J-W, Crystal Growth & Design, 10, (2010) 535
[12]
Feng, W., Xu, Y., Zhou., G. , Zhang, C., Zheng, X., Inorg. Chem. Comm. 10, 1(2007) 49 [33]
Chapter-1
[13]
Siddiqui, K. A., Bolte, M., Mehrotra, G. K., Inorg. Chimica Acta 363 (2010) 457
[14]
Wu, Z-F, Hu B , Feng, M-L, Huang X-Y,, Zhao, Y-B,, Inorganic Chemistry Communications 14 (2011) 1132
[15]
Xu, L., Choi, E-Y., Kwon, Y-U, Journal of Solid State Chemistry 181 (2008) 3185
[16]
Qiu, Y., Deng, H., Mou, J., Yang, S., Zeller, M., Batten S. R., Wu, H. and Li J., Chem. Commun. (2009) 5415
[17]
Wang, X-Li, Gao Q., Liu, G-C., Lin, H-Y, Tian, Ai-X., Li, J, Inorg. Chem. Comm. 14 (2011) 745
[18]
Wang, Y.-T., Fan, H.-H., Wang, He-Z., and Chen, X-M, Inorg. Chem., 44 (2005) 4148
[19]
James, Stuart L., Chem. Soc. Rev., 32 (2003) 276
[20]
Qiu, Y., Deng, H., Mou, J. Yang, S., Zeller, M., Batten, S. R., Wu, H. and Li, Cryst. Eng. Comm.,13 (2011) 2130
[21] (a) Tranchemontagne, D. J., Mendoza-Corte´s , J. L., Keeffe, M. O. and Yaghi, O. M. , Chem. Soc. Rev., 38 (2009) 1257 (b) Yaghi, O. M., Keeffe, M. O’, Ockwig, N. W., Chae, H. K., Eddaoudi, M. & Kim J., Nature 423 (2003) 705 [22]
Halper, S. R., Do L., Stork, J. R., and Cohen, S. M., J. Am. Chem. Soc. 128 (2006) 15255
[23]
Abrahams, B. F., P. Jackson, A. and Robson, R., Angew. Chem. Int. Ed., 1998, 37, 2656
[34]
Chapter-1
[24]
Dybtsev, D. N., Chun, H., Yoon, S. H., Kim, D. and Kim, K., J. Am. Chem. Soc., 126 (2004) 32
[25]
Lan, A., Li, K., Wu, H., Olson, D. H., Emge T. J., Ki, W., Hong M., and Li, J., Angew. Chem. Int. Ed., 48 (2009) 2334
[26]
Fujita, M., Kwon, Y. J., Washizu, S. and Ogura, K., J. Am. Chem. Soc., 116 (1994) 1151
[27]
Evans, O. R., Xiong, R.G., Wang, Z. Y., Wong, G. K. and Lin W., Angew. Chem. Int. Ed., 38 (1999) 536
[28]
Lee, J Y., Farha O. K., Roberts J., Scheidt, K. A., Nguyen, S.B. T. and Hupp, J. T.,Chem. Soc. Rev., 38 (2009) 1450
[29]
Chui, S. S., Lo, S. M., Charmant, J. P., Orpen, A. G. and Williams, I. D., Science, 283 (1999) 1148
[30]
Mackay, L. G., Wylie, R. S. and Sanders, J. K. M., J. Am. Chem. Soc., 116 (1994) 3141
[31] (a) Turova, N. Ya.; Kozunov, V. A,; Yanovskii, A. I.; Bokii, N. G.; Struchkov, Yu. T.; Tamopolskii, B. L. J. Inorg. Nucl. Chem. 41 (1979) 5 (b) Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, 0.; Hubert- Pfalzgraf, L. G. Polyhedron 10 (1991) 1639 (c) Cayton, R. H.; Chisholm, M. H.; Davidson, E. R.; Distasi, V. F.; Du, Ping; Huffman, J. C. Inorg. Chem. 30 (1991) 1020 (d) Healy, M. D.; Barron, A. R. Angew. Chem. 31 (1992) 921 [32] (a) Gupta, R.; Singh, A.; Mehrotra, R. C. Indian J. Chem. 30A (1991) 261 (b) Caulton, K. G.; Hubert-Pfalzgraf, L. G. Chem. Rev. 90 (1990) 969
[35]
Chapter-1
(c) Mehrotra, R. C., Transition Metal Alkoxides. Adu. Inorg. Chem. Radiochem. 26 (1983) 269 (d) Vandersluys, W. G.; Sattelberger, A. P. Chem. Reu. 90 (1990) 1027 (e) Mehrotra, R. C.; Singh, A.; Tripathi, U. M. Chem. Rev. 91 (1991) 1287 [33] (a) Smith H., Wark, M. J., Brinker, T. A., C. J. Coord. Chem. Rev. 112 (1992) 81 (b) Bradley, D. C. Chem. Rev. 89 (1989) 1317 [34] (a) Vandersluys, W. G.; Sattelberger, A. P. Chem. Reu. 90 (1990) 1027 (b) Sanchez, C.; Livage, J. New J. Chem. 14 (5) (1990) 13 [35]
Campion, J. F.; Payne, D. A,; Chae, H. K.; Maurin, J. K.; Wilson, S. R. Inorg. Chem. 30 (3) (1991) 245
[36]
Kuhlman, R.; Vaartstra, B. A,; Streib, W. E.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 32 (1993) 1272
[37] (a) Caulton, K. G.; Chisholm, M. H.; Drake, S. R.; Huffman, J. C. J. Chem. Soc., Chem. Commun. (1990) 1498 [38]
Sanchez, C.; Livage, J. New J. Chem. 14 (5) (1990) 13
[39] (a) Mehrotra, R. C. J . Non-Cryst. Solids 121 (1990) 1; 145 (1992) 1 (b) Mehrotra, R. C. Chemtracts 2 (1990) 389 (c) Livage, J., Henry, M., Sanchez, C. Prog., Solid State Chem. 18 (1988) 1317 [40]
Caulton, K. G.; Hubert-Pfalzgraf, L. G. Chem. Reu. 90 (1990) 969
[41]
Alkoxo and Aryloxo Derivatives of Metals, Elsevier (2001) ISBN: 978-012-124140-7
[42]
Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.;
[36]
Chapter-1
Ziller, J. W. Organometallics 3 (1984) 1563 [43]
Scholz, M.; Noltemeyer, M.; Roesky, H. W.Angew. Chem., 28 (1989) 1383
[44]
Mehrotra, R. C.; Rai, A. K. Polyhedron, 10 (1991) 1967
[45] (a) Turova, N. Y.; Kozunov, V. A, Yanovskii, A. I., Bokii, N. G., Struchkov, Y. T., Tamopolskii, B. L. J. Inorg. Nucl. Chem. 41 (1979) 5 (c) Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, 0.; Hubert- Pfalzgraf, L. G. Polyhedron 10 (1991) 1639 [46]
Ebelman, J.J., Ann., 57 (1846) 331
[47] (a) Baes C.F., Mesmer, R. F., The Hydrolysis of Cations, Wiley, New York, (1976) (b) Avnir, D., Kaufman, V. R., J. Non-Cryst. Solids, 192 (1987) 180 [48]
Barringer, E. A. and Bowen, H. K., J. Am. Ceram. Soc., C-199 (1982) 65
[49]
Scozzafava, M. R., Rhine, W. E., Cina, M. J., Better Ceramics through Chemistry IV, Mater. Res. Soc. Symp. Proc. 180 (1990) 697
[50]
Vaarttra, B. A., Huffman, J. C., Gradeff, P. S., Hubert-Pfalzgraf L. G., Daran, J. C., S., Yunlu, K. and Caulton, K.G., Inorg. Chem., 19 (1990) 3126
[51]
Toledano, P., Ribot, F. and Sanchez, C., Acta Cryst, C46 (1990) 1419
[52]
Eschwege V., Swarts, K. G., J. C., Polyhedron 24 (2005) 1727
[53]
Wengrovius, J. H., Carbauskas, M. F., Williams, E. A., Going, R. C., Donahue, P. E., and Smitb, J. F., J. Am. Chem. Soc. 108 (1986) 982
[54]
Pandey A., Pandey, A., Parak, W.J., Mayer P., Inorg. Chim. Acta 359 (2006) 4511
[37]
Chapter-1
[55] (a) Dislich, H., and Hinz, P., J. Non Cryst. Solids, 48 (1982) 11 (b) Dislich, H., Angew. Chem. 10 (1971) 363 [56] (a) Mazdiyasni, K.S., Dolloff, R.T., Smith, J. S., J. Am. Chem. Soc. 52 (1969) 523 (b) Smith, J. S., Dolloff, R.T., Mazdiyasni, M.S., J. Am. Ceram. Soc. 53 (1970) 91 (c) Lipeles, R. A., Coleman, D. J., In Ultrastructure Processing of Advanced Ceramics; Edited by Mackenzie, J. D., Ulrich, D. R.; Wiley; New York (1988) 919 [57] (a) Sakka, S., Kamiya, K., Malita, K. and Yammamoto, Y., J. Non-Cryst. Solids. 63 (1984) 223 (b) Sakka, S., Kamiya, K., J. Non Cryst. Solids, 57 (1983) 371 [58]
Guo, X., Hou, Wenhua, Ding, W., Fan, Y., Yan, Q., Chen, Yi, Inorganic Chemistry Communications 5 (2002) 946
[59]
Mathur, S., Veith, M., Ruegamer, T., Hemmer E., and Shen H., Chem. Mater., 16 (7) (2004) 1304
[60]
Veith, M., Mathur, S. and Mathur C., Polyhedron 17 (1998) 1005
[61]
Attar, A.S., Mirdamadi, S., Hajiesmaeilbaigi, F. and Ghamsari M.S., J. Mater. Sci. Technol., 23 (5) (2007) 611
[62]
Zhang, M., Bando, Y., Wada K., Journal of Materials Science Letters 20 (2001) 167 (a) Chen ,Y. W., Klemperer, W. B., Park, C. W., Mat. Res. Soc. Symp.Proc. 271 (1992) 57263
[63]
Kim, H.J., Yoon, Y.J., Kim, J.H., Nam, S.M., Materials Science and Engineering B161 (2009) 104 [38]
Chapter-1
[64]
Xiaobo Chen and Samuel S. Mao, Chem. Rev. 107 (2007) 2891
[65]
Kim, C.S., Kwon, I.M., Moon, B. K., Jeong, J. H., Choi, B.C., Kim, J. H., Choi, H., Yi, S. S., Yoo, D. H., Hong, K.S., Park, J.H., Lee, H. S., Mat. Sci. and Eng. C 27 (2007) 1343
[39]
CHAPTER 2 Metal Organic Frameworks (MOFs)
[40]
Chapter-2
Owing to their unique structural features and their potential applications as advanced materials the coordination compounds with tetrazole-based ligands have been the subject of intense research in recent years [1]. In the earlier literature tetrazoles have reportedly been synthesized by introducing expensive and toxic metals and these methods suffer from problems such as severe reaction conditions and risks of explosions [2]. Champness and Schroder in 1997 and Sharpless and co-workers in 2001 described a safe, convenient, and environment friendly synthetic route to 5-substituted 1H-tetrazoles with water as solvent and a zinc salt as catalyst [3, 4]. In contrast to direct tetrazole-synthesis the in situ hydrothermal method shows [2+3] cycloaddition of azides with nitriles along with several advantages like (a) reactions takes place in one step from the reactants (b) no need for separate synthesis of ligands (c) environment friendly (d) sufficient growth for single crystals [5]. Single crystals of the coordination polymers by hydrothermal methods under a number of conditions have successfully been isolated as the intermediates of these reactions. The structural investigations of these products are helpful in understanding the mechanism of the Demko–Sharpless reaction. Up to now, the in situ solvo/hydrothermal approach [612] has been extended to metals like Zn(II), Cu(I), Cd(II), Ag(I), Pb(I), Hg(II) etc. with cyanopyridines, 2-amino-5-cyanopyridine, MeCN, cyanobenzene, 4-methylbenzonitrile, malononitrile, dicyanopyridine, etc as ligands. Most of the coordinated metal centers in these compounds are derived from the used Lewis acids during the reactions. In this thesis we report the syntheses, structures, photoluminescence and thermal behavior of a some hydrothermally synthesized complexes.
[41]
Chapter-2
Table: Summary of all compounds (1-13)
S. N.
Compound
Physical state
Colour
Elemental analysis Calculated Found (%) (%)
C10H10N12Na2O2
Crystalline
White
C= 31.78 H=2.62 N=44.61
C=31.89 H=2.65 N=44.65
C10H10N12O2Zn
Crystalline
White
C=30.35 H=2.52 N=42.48
C=30.10 H=2.23 N=42.27
C=14.84 Colourless H=1.24 N=20.76
C=14.36 H=1.23 N=20.72
1.
2.
3. C10H10Cd3Cl4N12O2
Crystalline
CoH4N4C3O3
Powder
Red
C=17.74 H=1.98 N=27.60
C=18.06 H=1.88 N=28.32
CoH6N8C5O2
Powder
Pink
C=22.31 H=2.24 N=37.01
C=22.00 H= 2.12 N=36.56
C=21.66 H=1.48 N=39.82
C=23.04 H= 1.68 N=20.12
4.
5.
CoH4N6C4O2
Powder
Orange
C=21.16 H=1.77 N=37.01
CoH3N3C3.5O2
Powder
Orange
C=23.60 H=1.69 N=23.6
6.
7.
Cont…
[42]
Chapter-2
8.
BaH4N4C3O3
Powder
9.
BaH5N8C5.5O3
Powder
C=12.80 H=1.43 N=19.91
C=13.04 H=1.48 N=20.12
White
C=15.86 H=1.21 N=26.91
C=15.74 H=1.38 N=27.12
C=22.65 H=2.28 N=42.27
C=22.74 H=2.18 N=41.12
C=24.75 H=1.38 N=48.10
C=24.84 H=1.18 N=47.12
C=21.84 H=1.18 N=43.12
C= 18.84 H=1.17 N=35.12
White
10.
MnH6N8C5O2
Powder
Yellow
11.
CoH4N10C6O
Powder
Orangeyellow
SrH4N10C6O
Powder
Orange
C=22.54 H=1.20 N=43.80
BaH4N10C6O
Powder
White
C=19.5 H=1.09 N=37.90
12.
13.
[43]
Chapter-2
2.1 Synthesis and charectrization of Na2(Pzta)2(H2O)2]n: A novel coordination polymer of sodium [Na2(Pzta)2(H2O)2]n (1) has been synthesized hydrothermally by the reaction of pyrazine carbonitrile and sodium azide in the presence of aluminum(III) chloride as lewis acid catalyst (Scheme 1).
N
N
hydrothermal reaction
+ N
NaN3 + AlCl3 140°C, 50 h
CN
Na2 (H2O)2
N
N
N N
Scheme 1
2
N
Complex 1 represents the first hydrothermally synthesized 1D sodium monotetrazole coordination polymer. Strong hydrogen bonds are formed between water molecules and nitrogen atoms of both pyrazine and tetrazole rings which result in the formation of a 2D metallosupramolecular network. In the present synthesis we have used AlCl3 as a catalyst which is not only a strong Lewis acid but also known for lowering the reaction barrier [13]. Surprisingly, the resulting framework structure has been generated around sodium centers instead of aluminum. The first hydrothermally synthesized sodium ditetrazole coordination polymer was reported by Huang et al. [14] by hydrothermal treatment of ZnCl2 with NaN3 and 1,4-dicyano butylenes in the presence of NaOH octahedral
geometry
around
them.
wherein all the sodium centers have distorted The
mixed
metal
coordination
polymer
[CuNa2(tza)2(H2O)4]n [15], has also been reported which also has six coordination of the sodium atoms. Complex 1 was characterized by IR spectroscopy, elemental analysis, single-crystal Xray diffraction, thermal analysis (TGA/DTA) and solid state photoluminescence. [44]
Chapter-2
In the IR spectrum of complex 1 a peak over 3100 cm-1 (Figure 1) indicates the presence of coordinated water molecules. Furthermore, the absence of absorptions around 2300 cm-1 and ~ 2100 cm-1 suggests the absence of cyano and azide groups while the peaks in the range 1557-1447 cm-1 indicate that the [2+3] cycloaddition reaction between cyano group and azide anion has taken place. 90
80
Transmittance (%)
70
60
50
40
30
20 4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm )
Figure 1: IR spectrum of complex 1 The molecular composition of complex 1 was confirmed by elemental analysis. Single crystal X- ray analysis of compound 1: Complex 1 crystallizes in the triclinic space group P¯1. The asymmetric unit consists of two sodium atoms: Na1 exhibits distorted square pyramidal coordination geometry made by three N donors from the two pzta ligands and two oxygens from two water (one bridging and one terminal) molecules. Na2 is coordinated by four N atoms from three pzta groups and by one bridging water molecule, displaying distorted trigonal bipyramidal coordination geometry (Figure 2).
[45]
Chapter-2
Figure 2: ORTEP diagram (30% probability ellipsoids) showing the coordination environment of Na atoms in 1.
Complex 1 constitutes the first example of a sodium tetrazole complex with five coordination around the metal centers which is present in both trigonal bipyramidal and square pyramidal geometries. The Na–O distances are in the range of 2.3289(2) – 2.4260(2) Å (Table 1) while the Na– N bonds are in the range 2.3992(2) –2.5218(2) Å which are in accordance with previous reports [14]. In complex 1, the bond angle O–Na1–O is 98.14° and angles N–Na1–N are in the range of 69.53°-137.38° while angles O–Na1–N range from 89.55 to 170.29°. The bond angles O2-Na2-N around Na2 are in range of 89.3° to 106.4° while the angles N– Na2–N fall under the limit of 68.14–158.63°. In
the
sodium-tetrazolate
complex
reported
by
Huang
et
al.
each
ditetrazolylethylene acts as a tridentate bridging ligand while in 1, one of the two tetrazolylpyrazine moieties acts as a tridentate bridging ligand by coordinating to three different sodium centres (two Na1 type and one Na2) i.e. the tetrazolylpyrazine ligand of the one unit which is coordinated to Na1atom also coordinates to both sodium centre of
[46]
Chapter-2
the second unit through N4 and N5 atoms respectively. The other one tetrazolylpyrazine ligand is present as bridging bidentate ligand between the two sodium atoms (both Na2 type) i.e. the ligand which is coordinated to Na2 atom also coordinates to the Na2 atom of the third unit. The above mentioned two types of the bridging coordination of the tetrazolylpyrazine ligand results in the formation of 1D chain. It is noteworthy that the six sodium atoms, two oxygen atoms and eight nitrogen atoms (from four different tetrazolylpyrazine ligands) fabricate a sixteen membered sigmoid ring in 1D chain (Figure 3). As depicted in figure 3 there is a close layer packing of 1D layered loop chin formed by neutral [Na2(Pzta)2(H2O)2] repeating units utilizing pyrazinetetrazolyl metal coordination
mode
accompainied
by
the
bridging
ligands.
Thus
the
metallosupramolecular motif in 1 is neutral and due to the absence of charged groups the structure is an outcome of neutral-neutral type of H-bonding interaction. (a)
(b)
Figure 3: View of the crystal lattice along the b-axis showing; (a) 1D double chain coordination polymer. (b) the space filled diagram showing the sigmoid cavity. [47]
Chapter-2
The most remarkable feature of 1 is the molecular self-organization of the neutral [Na2(Pzta)2(H2O)2]
building blocks into
an 2D open framework (Figure 3) via
intermolecular hydrogen bonding interactions between the non-coordinated nitrogen atoms of the pyrazine and tetrazole ring and coordinated water molecules. The coordinated water molecules act as H-bond donor while pyrazinyl tetrazolate nitrogen atoms behave as acceptors. Of the three hydrogen bonding sites in the metal-complex building block, the one oriented along the c-axis is linked by wO-H---N bonds (between the bridging water molecule and pyrazine ring) via
(20) supramolecular synthons while the another two
are formed by the bridging and terminal water molecules which are linked to two different nitrogen atoms of the same tetrazole group via
(7) synthons (Figure 4).
(7)
Figure 4: 2D H-bonded metallo-supramolecular network [48]
Chapter-2
The formation of both type of H-bonding synthons result in the establishment of a 2D Hbonded network along the c-axis. The supramolecular synthons
(20) and
(7) appear
to have reliable utility for constructing a 2D supramolecular structure from 1D coordination chain.
Table 1: Selected bond lengths (Å) and bond angles (°) for compound 1 Na(1)-N(1) C(10)-N(9) Na(1)-N(3) C(10)-N(12) Na(1)-N(5) Na(2)-N(4) Na(2)-N(7) Na(2)-N(9) Na(2)-N(10) Na(1)-O(2) Na(2)-O(2) N(1)-C(1) N(1)-C(4) C(1)-C(2) N(2)-C(2) N(2)-C(3) C(3)-C(4) C(4)-C(5) C(5)-N(3) N(3)-N(4) N(4)- N(5) N(5)-N(6) N(7)-C(6) C(7)-N(8) N(8)-C(8)
2.5323(2) 1.3496(1) 2.4352(2) 1.3304(1) 2.3992(2) 2.4797(1) 2.5218(2) 2.5218(2) 2.4058(2) 2.3495(1) 2.4260(2) 1.3377(1) 1.3384(1) 1.3777(1) 1.3360(1) 1.3323(1) 1.3935(1) 1.4665(1) 1.3333(1) 1.3465(1) 1.3239(1) 1.3488(1) 1.3334(1) 1.3347(1) 1.3360(1)
N(7)-C(9) C(8)-C(9) N(8)-C(8) N(8)-C(8) N(10)-N(9) N(10)-N(11) N(11)-N(12) Na(1)-O(2)-Na(2) O(2)-Na(1)-N(3) O(2)-Na(1)-O(1) O(1)-Na(1)-N(1) N(1)-Na(1)-N(3) N(9)-Na(2)-N(9) N(10)-N(9)-Na(2) N(9)-N(10)-Na(2) N(10)-Na(2)-N(10) N(7)-Na(2)-N(9) Na(1)-N(4)-N(5) N(4)-N(5)-Na(2) N(1)-Na(1)-O(2) N(3)-Na(1)-O(2) N(4)-Na(2)-N(7) N(4)-Na(2)-N(9) N(9)-Na(2)-O(2) O(2)-Na(2)-N(7)
[49]
1.3457(1) 1.3858(1) 1.3360(1) 1.3360(1) 1.3496(1) 1.3154(1) 1.3534(1) 110.92 102.25 98.14 89.55 69.53 90.65 140.38 128.96 90.65 68.14 113.07 129.35 170.29 102.25 85.39 148.17 106.4 24.12
Chapter-2
Thermal analysis (TGA & DTA) of [Na2(Pzta)2(H2O)2]: Compound 1 was analyzed under inert atmosphere, while ramping the temperature at a rate of 10°C min-1 from 0 to 1200°C (Figure 5). The thermal decomposition profile of 1 showed that it is stable up to 225°C followed by one rapid weight loss in the temperature range 235-315°C corresponding to one molecule of water (calc. 4.22%, obsd. 4.78%). The weight loss between 315-357 °C attributed to the decomposition of one tetrazolato group (calc. 18.99%, obs. 20.37%) with exothermic reaction. Further in the temperature range of 357397 °C, the loss of the second water molecule has take place (calc. 6.20%, obs. 5.84%). 1.5 molecules of N2 was liberated between 397-460 °C (calc. 7.72%, obs. 9.72%) with highly exothermic reaction. In final step two pyrazine groups were released between 8471088°C (calc. 42.86%, obs. 40.56%) from the metal complex by leaving the cyano group on the metal atom which was further oxidized to give the final residue of sodium oxide with endothermic reaction [12].
60
TGA DTA
50
80
40
60
30
20 40 10
Heatflow / µV
Weight loss (%)
100
20 0 0
-10 0
200
400
600
800
1000
1200
o
Temp. C
Figure 5: Graph of TGA (black) and DTA (blue) of complex 1
[50]
Chapter-2
Photoluminesence (PL) properties of complex 1: The PL measurement of complex 1 was carried out in the solid state at room temperature. The free pzta ligand is known to exhibit blue fluorescent emission peak at 452 nm. As illustrated in figure 6, the complex 1 showed fluorescent emission band with maximum intensities at 436 nm upon excitation at 385 nm. Compared with free pzta (452 nm) [16], the emission peak is blue shifted in 1, which can tentatively be assigned to the intra-ligand transition of pzta modified by the coordination with metal. Since compound 1 has high thermal stability and is virtually insoluble in most common solvents such as acetone, methanol, chloroform, benzene, water etc. the emission property makes it a potential photoactive material.
Figure 6: The solid-state fluorescent spectrum of 1at room temperature, the blue line shows absorption where as red shows emission peak.
[51]
Chapter-2
2.2 Synthesis and charecterization of [Zn(Pzta)2(H2O)2] (2): A zinc complex with composition [Zn(pzta)2(H2O)2] (2), has been synthesized by heating a homogeneous mixture of Zn(OAc)2 .2H2O, pyrazine nitrile, sodium azide, H2O and ethyl alcohol in a hydrothermal bomb at 130⁰C for 32 h. After cooling the reaction mixture to room temperature white transparent cubic crystals were obtained (Scheme 2).
N
CN
N hydrothermal reaction
Zn(O2CCH3)2 + NaN3 + N
130oC, 32 h
N
N N N C N
Zn H2O 2 2
Scheme 2 It is noteworthy that under different sets of hydrothermal conditions ZnCl2 and Zn(NO3)2 are also known [1(n)] to give products of similar composition. This point towards the extra stability possessed by the structural framework of complex 2.
Complex 2 was characterized by IR spectroscopy, elemental analysis, thermal gravimetric analysis and single-crystal X-ray diffraction. The luminescence properties of 2 was also investigated at room temperature in the solid state. The IR spectrum of complex 2 having a peak over 3300 cm-1 (Figure 7) indicates the presence of coordinated water molecules. Furthermore, the reduction of absorptions around 2300 cm-1 and ~ 2100 cm-1 are indicative of the absence of cyano and azide groups while the band in the range 1557-1447 cm-1 indicate that the [2+3] cycloaddition reaction between cyano group and azide anion has taken place.
[52]
Chapter-2
Transmittance (%)
100
80
60
40
20
0 4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm )
Figure 7: IR spectrum of complex 2
Single crystal X- ray analysis of complex 2: Complex 2 crystallizes in the monoclinic P 2 1/n space group (Figure 8). Zn atoms in complex 2 exhibit slightly distorted octahedral geometry. The metal atoms are present at the symmetry center and chelated by two deprotonated pyrazinetetrazolate ligands having the trans configuration. Two pyrazine nitrogen atoms and two tetrazole nitrogens from different pzta ligands build the equatorial plane around the Zn(II) ions. The two terminal water molecules complete the octahedral coordination of Zn(II).
[53]
Chapter-2
Figure 8: Ball stick model of complex 2
(17)
Figure 9: H-bonded open metallo-supramolecular network showing supramolecular synthons. [54]
Chapter-2
(a)
(b) (10 )
Figure 10: 2D chain hydrogen bonding (a) and metal positions in the crystal lattice (b) The complex 2 extends through two types of hydrogen bonding interactions which result in the formation of the supramolecular structure. Of the two hydrogen bonding sites in the metal-complex building block, the one oriented along the c-axis is linked by wO-H---N (2.004 Å) bonds between water molecule and pyrazine tetrazole via (10) supramolecular synthons. The another one formed by the other water molecule which are linked to two different nitrogen atoms of the different tetrazole group of other molecule via
(17) synthons (wO---H---N are 1.908 Å and 2.004 Å). The formation of
both type of H-bonding synthons results in the establishment of a 2D H-bonded network along the c-axis. In the complex 2 the Zn-N bond lengths are 2.197(2) Å & 2.117(2)Å while the Zn-O1W, is 2.102(2) Å (Table 2). In the complex 2 the bond angle O1W-Zn1-O1W is 180 ⁰C and angles O1W-Zn1-N are in the range of 87.65(7)⁰ - 89.88(7)⁰, while the angle N1-Zn1-N3 is 78.52(6)⁰ (Table 3) which are in accordance with previous reports [1(n)]. [55]
Chapter-2
Table 2: Selected bond lengths (Å) for compound 2 Atom1 Zn(1) Zn(1) Zn(1) O(1)W O(1)W N(1) N(1) N(2) N(2) N(3) N(3) N(4) N(5) N(6) C(1) C(1) C(2) C(3) C(3) C(4)
Atom2 O(1)W N(1) N(3) H(1)W(1) H(1)W(2) C(1) C(4) C(2) C(3) N(4) C(5) N(5) N(6) C(5) C(2) H(1) H(2) C(4) H(3) C(5)
[56]
Distance 2.102(2) 2.197(2) 2.117(2) 0.84(2) 0.85(2) 1.331(3) 1.340(2) 1.328(3) 1.329(3) 1.336(2) 1.334(3) 1.312(3) 1.336(3) 1.322(2) 1.382(3) 0.95(2) 0.95(1) 1.384(3) 0.95(2) 1.460(2)
Chapter-2
Table 3: Selected bond angles (°) for compound 2
Atom1 O(1)W O(1)W O(1)W O(1)W O(1)W N(1) N(1) N(1) N(1) N(3) N(3) N(3) O(1)W O(1)W N(1) Zn(1) Zn(1) H(1)W(1) Zn(1) Zn(1) C(1) C(2)
Atom 2 Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) Zn(1) O(1)W O(1)W O(1)W N(1) N(1) N(1) N(2)
Atom3 N(1) N(3) O(1)W N(1) N(3) N(3) O(1)W N(1) N(3) O(1)W N(1) N(3) N(1) N(3) N(3) H(1)W(1) H(1)W(2) H(1)W(2) C(1) C(4) C(4) C(3)
Angle 89.88(7) 87.65(7) 180.00(7) 90.12(7) 92.35(7) 78.52(6) 90.12(7) 180.00(6) 101.48(6) 92.35(7) 101.48(6) 180.00(7) 89.88(7) 87.65(7) 78.52(6) 116(2) 119(2) 115(2) 130.8(1) 112.3(1) 116.9(2) 116.2(2)
[57]
Atom1 N(1) C(2) N(2) N(2) C(1) N(2) N(2) C(4) N(1) N(1) C(3) N(3) N(3) N(6) Zn(1) Zn(1) N(4) N(3) N(4) N(5) N(1)
Atom 2 C(1) C(1) C(2) C(2) C(2) C(3) C(3) C(3) C(4) C(4) C(4) C(5) C(5) C(5) N(3) N(3) N(3) N(4) N(5) N(6) C(1)
Atom3 H(1) H(1) C(1) H(2) H(2) C(4) H(3) H(3) C(3) C(5) C(5) N(6) C(4) C(4) N(4) C(5) C(5) N(5) N(6) C(5) C(2)
Angle 117(1) 121(1) 122.1(2) 117(1) 121(1) 122.4(2) 119(1) 119(1) 120.8(2) 115.8(2) 123.4(2) 111.4(2) 121.0(2) 127.6(2) 142.4(1) 112.3(1) 105.0(2) 109.0(2) 109.5(2) 105.1(2) 121.5(2)
Chapter-2
Thermal
gravimetric
analysis
(TGA)
of
[Zn(pzta)2(H2O)2]:
The
thermal
decomposition graph of 2 (Figure 11) is showing that it is stable up to 186°C followed by one rapid weight loss in the temperature range 189-262°C corresponding to one molecule of water (calc. 4.5%, obsd. 4.6%). The weight loss between 262-300°C can be attributed to the decomposition of one tetrazolato group N2 (calc. 17.45%, obsd. 16.30%). The weight loss between 300-445°C was due to the libration of one molecule of N2 and one molecule of water (calc. 11.6%, obs. 10.54%). In the temperature range 470-684°C the degradation of the pyrazine and cyano groups from the metal complex have taken place while the metal atom was further oxidized to give the final residue of zinc oxide [12].
110 100 90
Wt (%)
80 70 60 50 40 30 100
200
300
400
500
600
700
800
o
Temp. C
Figure 11: The thermal decomposition profile of compound 2
[58]
Chapter-2
Photoluminesence (PL) properties of complex 2: The PL measurement was carried out in the solid state at room temperature. The free pzta ligand exhibits [17] blue fluorescent emission band at 452 nm upon the excitation at around 385 nm. The complex emits with a maximum at 395.5 nm upon the excitation at around 385 nm (Figure 12). The emission peak is blue shifted in the complex 2, which can tentatively be assigned to the intraligand transition of pzta due to the metal coordination. Since compound 2 is highly thermal stabile and insoluble in most common solvents such as acetone, methanol, chloroform, benzene, water etc. with a significant emission property, making it an important photoactive material for various applications.
Intensity (a.u.)
395.56
380
400
420
440
460
480
500
Wavelength (nm)
Figure 12: The solid-state fluorescent spectrum of 2 at room temperature shows emission peak. [59]
Chapter-2
2.3 Synthesis and charecterization of [Cd3(pzta)2(μ-Cl)4(H2O)2]n (3): As a continuation of our studies on novel metal complexes produced during in situ [2+3] cycloaddition reaction systems, we have carried out the cycloaddition reaction of pyrazine carbonitrile with NaN3 in the presence of CdCl2 and H3PO4 (Scheme 3). Herein, we report the synthesis, crystal structrure, photoluminescence and thermal behavior of a novel cadmium tetrazole complex [Cd3(pzta)2(μ-Cl)4H2O)2]n (3).
N CdCl2.2H2O
NaN3 N
CN H3PO4, H2O o
N
Cd3
135 C, 48h
N
N N N C N 2
Cl4 H2O 2
Scheme 3 Complex 3 was characterized by IR spectroscopy, elemental analysis, single-crystal Xray diffraction, thermal gravimetric analysis and solid state photoluminescence property. The IR spectrum of the title complex 3 exhibits several characteristic strong and medium bands (Figure 13). The ligand has several potential donor sites which have the tendency to coordinate with the metal ions. IR spectrum of the cadmium complex, [Cd3(pzta)2(μCl)4H2O)2]n, the absence of absorptions around 2300 cm-1 indicates the absence of cyano while the peaks in the range of 1557-1447 cm-1 indicate that the [2+3] cycloaddition reactiotn between cyano group and azide anion has taken place. A broad band over 3100 cm-1 assigned to the presence of coordinated water molecules.
[60]
Chapter-2
80
Transmittance(%)
70
60
50
40
30
20
10 4000
3500
3000
2500
2000
1500
1000
500
-1
Wavelength(cm )
Figure 13: IR spectrum of complex 3
Single crystal X-ray analysis of complex 3: Single crystal X- ray analysis reveals that the local coordination geometry around all the three cadmium atoms can be best described as slightly distorted six-coordinated octahedron where the angles subtended at the metal centre vary from 70.96(6)° to 95.71(4)°. As shown in Figure 14, the trinuclear complex is a centrosymmetric dimer with Cd1 locating at the inversion centre, which consists of one and a half crystallographically independent Cd(II) ions, one bridging pyrazine tetrazole ligand; four chlorine atoms and a water molecule. All the four chlorine atoms are bridging while the water molecule is terminal in position. In complex 3 protonated water molecule is present (condition like oxonium ion) which may be due to the higher acidity of the reaction owing to the presence of orthophosphoric acid. The bond angle of oxygen with H12 and H13 have the normal bond angle (like in water) but the value is changed with H11 i.e. 119 ° which is closest to angle of oxonium ion. [61]
Chapter-2
From the above data it is concluded that H11 attached with the oxygen of water, is not the real hydrogen of water, it is generated due to the use of highly acidic rection mixture The centrosymmetric Cd1 is coordinated to four bridging chlorine atoms; two pyrazinyl N donors from two individual pzta ligands. And the octahedral Cd2 is defined by three N donors from the two separate pzta ligands; two bridging chlorine atoms and O of water molecule.
Figure 14: Ball-stick diagram showing the coordination atmospheres of Cd atoms in 3
In the cadmium-tetrazolate complex both the tetrazolylpyrazine moieties act as tetradentate bridging ligand by coordinating with cadmium atoms of two neighbouring units resulting in the formation of a 1D helical chain (Figure 15).
Figure 15: View of the crystal lattice showing the 1D helical chain formed by bridging pzta ligand. [62]
Chapter-2
The Cd2–O1 distance is 2.3279(16) Å while the Cd –N and Cd –Cl bond lenghts are in the range of 2.239(2) – 2.4171(2) and 2.5500(7) – 2.6344(7) Å respectively, which are comparable to those reported values [16]. The bond angles O–Cd2–N around Cd2 are in the range of 83.96°–91.68° while angles O–Cd2–Cl range from 90.39° to 175.42°. In 3 the bond angles N–Cd2–N are in the range from 70.09° to 180° while the angles fall under the limit of 86.42°. Selected bond lengths and bond angles are given in Table 4 and 5. (a)
(b)
Figure 16: View of the crystal lattice along the c-axis showing; (a) ABAB type between two adjacent layers in 1 (For clarity, some atoms in ligand are omitted). (b) The space filled diagram showing two types of microporous cavities of the dimension 11.853 X 9.658 Å and 8.578 X 8.395 Å. Further, the propagation of the helical with μ2-Cl- ions ultimately leads to the formation of the two dimensional coordination polymer with two distinct holes in each sheet, the larger hole of the dimension 11.853 X 9.658 Å and the smaller hole of the dimension 8.578 X 8.395 Å along the c-axis (based on Cd–Cd distance) as shown in Figure 16. The crystal structure of 3 shows the self organizing behavior of [Cd3(pzta)2(μ-Cl)4H2O)2] building blocks and a variety of hydrogen bonding synthons formed via intermolecular neutral hydrogen bonding between the coordinated water molecules and non-coordinated nitrogen atoms of the tetrazole to configure a supramolecular microporous 3D network. [63]
Chapter-2
The coordinated water molecules act as H-bond donor while tetrazolyl nitrogen atoms behave as acceptors. The hydrogen bonded site in crystal lattice of complex 3 is oriented b-axis is linked by wO-H---N bonds (between the bridging water molecule and tetrazole ring) via and
(26)
(12) supramolecular synthons (Figure 17). Formation of both types of
supramolecular synthons results in the establishment of a 3D supramolecular network along the b-axis (Figure 18). In 3, the N---O bond distance is 2.727 Å, and the N---H---O bond angle of the intermolecular hydrogen bond is 164.81°.
It is noteworthy that in the crystal packing of 3, the noncovalent binding forces play an important role in the stabilization of the complex and propagation of the low dimensional structure to a 3D framework due to robust hydrogen bonding interactions involving a variety of supramolecular synthons such as
(26) and
(12). The 2D network is joined
in the third dimension by wO-H---N interactions. Thus, the supramolecular synthons (26) and
(12) appear to have reliable utility for constructing a 3D supramolecular
structure from 2D coordination chain. In conclusion, we have synthesized and characterized a new Cd-tetraazolate complex of the formula [Cd3(pzta)2(μ-Cl)4H2O)2]n (3), in which the pzta ligand is coordinating in a bridging fashion along with water molecules connecting three metal ions. Interplay of weak non-covalent forces between water molecules and the N atoms of tetrazole results in the formation of a microporous 3D framework. The supramolecular synthons are acting as molecular junctions which play a pivotal role in controlling the crystal packing.
[64]
Chapter-2
This work together with our previous contributions [17], further supplements Sharpless’ cycloaddition reactions of azides and nitriles by using Lewis acid as catalyst.
(26)
(12)
Figure 17: H-bonded open metallo-supramolecular network showing supramolecular synthons. It is noteworthy that in the crystal packing of 3, the noncovalent binding forces play an important role in the stabilization of the complex and propagation of the low dimensional structure to a 3D framework due to robust hydrogen bonding interactions involving a variety of supramolecular synthons such as
(26) and
[65]
(12).
Chapter-2
The 2D network is joined in the third dimension by wO-H---N interactions. Thus, the supramolecular synthons
(26) and
(12) appear to have reliable utility for
constructing a for constructing a 3D supramolecular structure from 2D coordination chain (Figure 18).
Figure 18: View of the crystal lattice showing the 3D H-bonded metallo-supramolecular network along b-axis.
[66]
Chapter-2
Table 4: Selected bond lengths (Å) for compound 3 Atom1 Cd(1) Cd(1) Cd(1) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cl(1) Cl(2) O(1) O(1) O(1) N(1) N(1) N(2) N(2) N(3) N(3) N(4) N(4) N(5) N(6) C(1) C(1) C(2) C(3) C(3) C(4)
Atom2 Cl(1) N(1) Cl2) Cl(2) O(1) N(2) N(3) Cl(1) N(4) Cd(2) Cd(1) H(11) H(12) H(13) C(1) C(4) C(2) C(3) N(4) C(5) N(5) Cd(2) N(6) C(5) H(1) C(2) H(2) C(4) C(5) H(4)
[67]
Length 2.6276(6) 2.411(2) 2.6036(6) 2.6344(7) 2.328(2) 2.417(2) 2.357(2) 2.5500(7) 2.284(2) 2.5500(7) 2.6036(6) 0.81(1) 0.82(5) 0.82(3) 1.340(3) 1.339(3) 1.335(3) 1.342(3) 1.342(3) 1.330(2) 1.320(3) 2.284(2) 1.335(2) 1.335(3) 0.950(2) 1.390(2) 0.950(2) 1.391(2) 1.463(3) 0.950(2)
Chapter-2
Table 5: Selected bond angles (°) for compound 3 Atom1 Cl(1) Cl(1) Cl(1) Cl(1) N(1) N(1) Cl(1) N(1) Cl(2) Cl(2) Cl(2) Cl(2) Cl(2) Cl(2) O(1) O(1) O(1) O(1) N(2) N(2) N(2) N(3) N(3) Cd(1) Cd(2) Cd(2) Cd(2)
Atom2 Cd(1) Cd(1) Cd(1) Cd(1) Cd(1) Cd(1) Cd(1) Cd(1) Cd(1) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cd(2) Cl(1) Cl(2) O(1) O(1)
Atom3 N(1) Cl(1) N(1) Cl(2) N(1) Cl(2) Cl(2) Cl(2) Cl(2) O(1) N(2) N(3) Cl(1) N(4) N(2) N(3) Cl(1) N(4) N(3) Cl(1) N(4) Cl(1) N(4) Cd(2) Cd(1) H(12) H(13)
Angle 84.29(5) 180.00(2) 95.71(5) 86.42(2) 180.00(7) 90.75(5) 93.58(2) 89.25(5) 180.00(2) 175.42(5) 92.07(5) 89.18(5) 87.38(2) 92.75(5) 83.96(7) 91.60(6) 90.38(5) 91.67(7) 70.09(7) 90.60(5) 164.31(7) 160.25(5) 95.05(7) 93.62(2) 92.23(2) 121(4) 113(3)
Atom1 Atom2 H(11) O1) H(12) O(1) Cd(1) N(1) Cd(1) N(1) Cd(2) N(2) Cd(2) N(2) C(2) N(2) Cd(2) N(3) Cd(2) N(3) N(4) N(3) N(3) N(4) N(3) N(4) N(5) N(4) N(4) N(5) N(5) N(6) N(1) C(1) N(1) C(1) H(1) C(1) N(2) C(2) N(2) C(2) C(1) C(2) N(2) C(3) N(2) C(3) C(4) C(3) N(1) C(4) N(1) C(4) C(3) C(4) N(3) C(5)
[68]
Atom3 H(13) H(13) C(1) C(4) C(2) C(3) C(3) N(4) C(5) C(5) N(5) Cd(2) Cd(2) N(6) C(5) H(1) C(2) C(2) C(1) H(2) H(2) C(4) C(5) C(5) C(3) H(4) H(4) N(6)
Angle 118(4) 91(5) 121.6(2) 121.1(2) 126.4(2) 116.2(1) 117.2(2) 140.0(1) 115.4(1) 104.4(2) 110.1(2) 124.8(1) 125.1(2) 108.5(2) 105.4(2) 119.3(2) 121.4(2) 119.3(2) 121.5(2) 119.2(2) 119.3(2) 121.3(2) 115.4(2) 123.2(2) 121.4(2) 119.3(2) 119.3(2) 111.6(2)
Chapter-2
Thermal analysis (TGA & DTA) of [Cd3(pzta)2(μ-Cl)4(H2O)2]: The Compound 3 was Compound 1 was analyzed by thermogravimetric analysis (TGA) under inert atmosphere, while ramping the temperature at a rate of 10°C min-1 from 0 to 1100°C (Figure 19). The thermal decomposition profile of 1 indicated that it was stable up to 280 °C followed by a rapid weight loss in the temperature range 280-336°C corresponding to the loss of two interstitial or coordinated water molecule (calc. 4.44%,obsd. 4.18%). The weight loss between 378-788 °C has been attributed to the decomposition of one tetrazolato group and four Cl atoms. (calc. 26.61%, obs. 25.57%). In the temperature range 432-617 °C, 1.5 molecules of N2 and one pyrazine group were liberated (calc. 21.52%, obs. 20.92%). Finally remainig pyrazine group was released from the metal complex and the cyano group left on the metal atom was further oxidized to give the cadmium oxide residue [12].
50 100
TGA DTA
40
80
20 40
10
20
0
0
0
200
400
600
800
1000
o
Temp. C
Figure 19: Plot of TGA/DTA of complex 3 [69]
1200
Heatflow / µV
Weight Loss (%)
30 60
Chapter-2
Photoluminesence (PL) properties of complex 3: Among all fluorescent materials with potential applications in light-emitting devices, the d10 metal (CuI, AgI, AuI, ZnII, CdII), complexes have been studied most extensively. The pzta ligand with its extended aromaticity is regarded to be a good candidate for enhanced emissive properties. Photofluorescent measurements of the complex 3 were carried out in the solid state at room temperature. The free pzta ligand exhibits blue fluorescent emission band at 452 nm. As illustrated in Figure 20, complex 3 upon excitation at 385 nm shows fluorescent emission band with maximum intensity at 429 nm. However, the UV-Vis absorption spectrum of aqueous solution of 3 shows a strong band around 325nm is tentatively assigned to ligands to metal charge transfer transitions. Compared with free pzta (452 nm) [17], the emission peak is blue shifted in 3, which may be ascribed to the cooperative effects of intraligand emission and ligand-to-metal charge transfer (LMCT). Since compound 3 has high thermal stability and is virtually insoluble in most common solvents such as acetone, methanol, chloroform, benzene, water etc., the emission property makes it a potential photoactive material.
Figure 20: The solid-state fluorescent spectrum of 3 at room temperature blue for absorbance and red for emission. [70]
Chapter-2
Some synthesized metal organic framework compounds are characterized by IR spectroscopy and elemental analysis. The formation of tetrazole group is confirmed by the FT-IR spectroscopy. Their single crystals were not obtained for X-ray crystallography, therefore, their empirical formula are etabilished only on the basis of elemental analysis. 2.4 Synthesis and characterization of compound CoH4N4C3O3 (4): The compound of cobalt with composition CoH4N4C3O3 (4) was synthesized by the reaction of cobalt chloride, sodium azide and cyanoacetic acid in water under hydrothermal condition at 160oC for 24h (Scheme 4). H2O CoCl2.6H2O + NaN3 + NCCH2COOH
Co2
160oC, 24h
O C O CH
2
Scheme 4
N
N N N 2
H2O
2
The composition of the compound 4 has been established on the basis of elemental analysis.
90 80
Transmittance (%)
70 60 50 40 30 20 10 4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm )
Figure 21: IR spectrum of complex 4 In the IR spectrum of 4 the peak over 3400 cm-1 (Figure 21) indicates the presence of coordinated water molecules. The peaks in the range 1557-1447 cm-1 indicate the
[71]
Chapter-2
formation of tetrazole by [2+3] cycloaddition reaction between cyano group and azide anion. 2.5 Synthesis and characterization of compound CoH6N8C5O2 (5): The compound of cobalt having composition CoH6N8C5O2 (5) was synthesized by the reaction of cobalt chloride, sodium azide, acetylmalononitrile and water under hydrothermal condition at 160oC for 24h (Scheme 5). H2O Co2
CoCl2.6H2O + NaN3 + CH3COCH(CN)2
CH3
O N N C C N CH N
H2O
o
160 C, 24h N N N N
Scheme 5
2
2
The composition of the compound 5 has been established on the basis of elemental
Transmittance (%)
analysis.
4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber(cm )
Figure 22: IR spectrum of compound 5 In the IR spectroscopy spectrum in figure 5 peak over 3250 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicate tetrazole that formed by [2+3] cycloaddition reaction between cyano group and azide anion.
[72]
Chapter-2
2.6 Synthesis and characterization of compound CoH4N6C4O2 (6): The compound of cobalt having composition CoH4N6C4O2 (6) was synthesized by the reaction of cobalt chloride, sodium azide, acetylmalononitrile, water and ethanol under hydrothermal condition at 110oC for 35h (Scheme 6). CoCl2.6H2O + NaN3 + CH3COCH(CN)2 +NCCH2COOH
110oC, 35h
Co4
O C C H O
2
H2O
N
N N N 2
O N N C C N CH N
CH3
N N N N
H2O
2
2
Scheme 6 The composition of the compound 6 has been established on the basis of elemental analysis. 90
Transmittance (%)
80
70
60
50
40
30
20 4500
4000
3500
3000
2500
2000
1500
1000
-1
Wave number (cm )
Figure 23: IR spectrum of compound 6
[73]
500
Chapter-2
In IR spectrum, peak over 3250 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicate the presence of tetrazole that formed by [2+3] cycloaddition reaction between cyano group and azide anion. 2.7 Synthesis and characterization of compound CoH3N6C3.5O2 (7): The compound of cobalt with composition CoH3N3C3.5O2 (7) was synthesized by the reaction of cobalt chloride, sodium azide, cyanoacetic acid and 4-cynobenzoic acid in ~15mL water and ethanol under hydrothermal condition at 110oC for 35h (Scheme 7). CN
CoCl2.6H2O + NaN3 + NCCH2COOH +
110oC, 35h
O C C H O
Co4
N
COOH
H2O
O C O
N N
N N N N N 2
2
H2O
2
Scheme 7 The composition of the compound 7 has been established on the basis of elemental analysis.
Transmittance (%)
100
80
60
40
20
4500
4000
3500
3000
2500
2000
1500
1000
-1
wavenumber (cm )
Figure 24: IR spectrum of compound 7
[74]
500
Chapter-2
In IR spectrum, peak over 3400 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicates the formation of tetrazole by [2+3] cycloaddition reaction between cyano group and azide anion. 2.8 Synthesis and characterization of compound BaH4N4C3O3 (8): The compound of barium having composition BaH4N4C3O3 (8) was synthesized by the reaction of barium chloride, sodium azide and cynoacetic acid in ~15mL water under hydrothermal condition at 160oC for 24h (Scheme 8). H2O
O C C H O
Ba2
BaCl2.2H2O + NaN3 + NCCH2COOH 110 oC, 24h
2
Scheme 8
N N N N 2
H2O
2
The composition of the compound 8 has been established on the basis of elemental analysis. 140
Transmittance(%)
130 120 110 100 90 80 70 60 4500
4000
3500
3000
2500
2000
1500
1000
500
-1
wave number (cm )
Figure 25: IR spectrum of compound 8 In the IR spectroscopy spectrum peak over 3230 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicate tetrazole group that formed by [2+3] cycloaddition reaction between cyano group and azide anion.
[75]
Chapter-2
2.9 Synthesis and characterization of compound BaH5N8C5.5O3 (9): The compound of barium with composition BaH5N8C5.5O3 (9) was synthesized by the reaction of barium acetate, sodium azide, cynoacetic acid, acetylmalononitrile, water and ethanol under hydrothermal condition at 110oC for 24h (Scheme 9). Ba(OOC-CH3)2+ NaN3 + NCCH2COOH + CH3COCH(CN)2
110oC, 24h
CH3
Ba2
O N N C C N CH N
H2O
O C C H O
2
N N N N
N N N N 2
H2O
Scheme 9
The composition of the compound 9 has been established on the basis of elemental analysis. In IR spectrum, peak over 3220 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicate tetrazole that formed by [2+3] cycloaddition reaction between cyano group and azide anion.
Transmittance(%)
110
100
90
80
70
60 4500
4000
3500
3000
2500
2000
1500
1000
-1
wave number (cm )
Figure 26: IR spectrum of compound 9
[76]
500
Chapter-2
2.10 Synthesis and characterization of compound MnH6N8C5O2 (10): The compound of manganese with composition MnH6N8C5O2 (10) was synthesized by the reaction of manganese chloride, sodium azide and acetylmalononitrile in ~15mL water and ethanol under hydrothermal condition at 160oC for 36h (Scheme 10). H2O, C2H5OH MnCl2.4H2O + NaN3 + CH3COCH(CN)2
Mn2
CH3
160oC, 36h
O N N C C N CH N
H 2O
N N N N
2
2
Scheme 10 The composition of the compound 10 has been established on the basis of elemental analysis. In IR spectrum peak over 3170 cm-1 indicates the presence of coordinated water molecules. The peaks in the range 1557-1447 cm-1 indicate the formation of group tetrazole by [2+3] cycloaddition reaction between cyano group and azide anion. 40
Transmittance (%)
35 30 25 20 15 10 5 0 4000
3500
3000
2500
2000
1500 -1
Wavenumber (cm )
Figure 27: IR spectrum of compound 10
[77]
1000
500
Chapter-2
2.11Synthesis and characterization of compound CoH4N10C6O (11): The compound of cobalt having composition CoH4N10C6O (11) was synthesized by the reaction of cobalt chloride, sodium azide and 2,3-pyrazinedicarbonitrile in ~15mL water and ethanol under hydrothermal condition at 110oC for 24h (Scheme 11). N N
NC
H2O, C2H5OH
N
CoCl2.6H2O + NaN3 +
N NC
o
110 C, 24h
N
N N N N
N N N
Co2 (H2O)2 2
Scheme 11
The composition of the compound 11 has been established on the basis of elemental analysis. In IR spectrum, peak over 3365 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicates tetrazole synthesis by [2+3] cycloaddition reaction between cyano group and azide anion.
Transmittance (%)
2.5
2.0
1.5
1.0
0.5
0.0 4000
3500
3000
2500
2000
1500 -1
Wavenumber (cm )
Figure 28: IR spectrum of compound 11
[78]
1000
500
Chapter-2
2.12 Synthesis and characterization of compound SrH 4N10C6O (12): The compound of strontium having composition SrH4N10C6O (12) was synthesized by the reaction of strontium acetate, sodium azide, 2,3-pyrazinedicarbonitrile, water and THF under hydrothermal condition at 110oC for 24h (Scheme 12). N
NC
N
H2O, THF
N
110oC, 24h
Sr(OOC-CH3)2. 1/2H2O + NaN3 + NC
N N
Scheme 12
N N N
Sr2 (H2O)2 N 2 N N N
The composition of the compound 12 has been established on the basis of elemental analysis. In IR spectrum, peak over 3160 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicates tetrazole group by [2+3] cycloaddition reaction between cyano group and azide anion. 0.35
0.30
Transmittance (%)
0.25
0.20
0.15
0.10
0.05
0.00 4000
3500
3000
2500
2000
1500 -1
Wavenumber (cm )
Figure 29: IR spectrum of compound 12
[79]
1000
500
Chapter-2
2.13 Synthesis and characterization of compound BaH4N10C6O (13): The compound of barium having composition BaH4N10C6O (13) was synthesized by the reaction of barium acetate, sodium azide, 2, 3-pyrazinedicarbonitrile, water and tetahyrofuron (THF) under hydrothermal condition at 110oC for 24h (Scheme 12). N
NC
N
H2O, THF
N
NC
N
110oC, 24h
N
Ba(OOCCH3)2 + NaN3 +
Scheme 13
N N N
Ba2 (H2O)2 N 2 N N N
The composition of the compound 13 has been established on the basis of elemental analysis. In IR spectrum peak over 3254 cm-1 indicates the presence of coordinated water molecules. The peak in the range 1557-1447 cm-1 indicates tetrazole formed by [2+3] cycloaddition reaction between cyano group and azide anion. 80 70
Transmittance (%)
60 50 40 30 20 10 0 4000
3500
3000
2500
2000
1500
1000
-1
Wavenumber (cm )
Figure 30: IR spectrum of compound 13
[80]
500
Chapter-2
However in the absence of the single crystal X-ray analysis it has unfortunately not been possible to comment on the molecular and framework structures of the complexes 4-13. Experimental All the metal salts were purchased from the Qualigen Pvt. Ltd. India and all the organic compounds from Sigma Aldrich Pvt. Ltd. All these compounds were used without any further purification. All solvents were distilled prior to use. IR spectroscopy was done by Perkin Elmer PE 1600FTIR in KBr, elemental analysis by Perkin-Elmer 240C Elemental Analyser and single crystal X-ray analyses were carried out using a 'Oxford XCalibur' diffractometer. Thermal studies (TGA & DTA) were performed on a Simultaneous Thermal Analyzer (STA 6000) and photoluminescence (PL) analysis by a Perkin-Elmer LS 45 luminescence spectrometer. Synthesis of [Na2(Pzta)2(H2O)2]n (1): Compound 1 was synthesized by a mixture of AlCl3 (0.410 g; 3.0 mmol), pyrazinecarbonitrile (0.312 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), C2H5OH (5 ml) and H2O (10 ml) was sealed in a 20 ml teflon-lined reactor which was heated in an oven to 140°C for 50h (Scheme 1), then cooled to room temperature at a rate of 5°C h-1. The resultant solution was allowed slowly to evaporate at room temperature for several weeks to give plate crystals of 1 (yield: 61%). From the elemental analysis calc. for C10H10N12Na2O2 (376.246): cal. C, 31.78%; H, 2.62% and N, 44.61% whereas found: C, 31.89%; H, 2.65% and N, 44.65%. IR (KBr, cm−1): 3441(m), 3048 (w), 1623 (w), 1540 (s), 1427 (m), 1340 (s), 1280 (s), 1180 (m), 1155 (s), 1070 (m), 1018 (s), 952 (w), 891(m), 771(m).
Synthesis of [Zn(pzta)2(H2O)2]n (2): Compound 2 was synthesized by a mixture of Zn(O2CCH3)2. H2O (0.658 g; 3.0 mmol), pyrazinecarbonitrile (0.312 g; 3.0 mmol), NaN3 [81]
Chapter-2
(0.195 g; 3.0 mmol), C2H5OH (5 ml) and H2O (10 ml) ( sealed in a 20 ml teflon-lined reactor) which was heated in an oven to 130°C for 48h, then cooled to room temperature at a rate of 5°C h-1. The resultant solution was allowed slowly to evaporate at room temperature for several weeks to give plate type white crystals of 2 (yield: 74%). From the elemental analysis for formula ZnC10H10N12O2 (395.67): calc. C 30.356%, H 2.527% and N 42.48% found: C 30.10%, H 2.23 and N 42.27%. IR (KBr, cm-1):3425(m), 2814(w), 2451(s), 1752(w), 1428(s), 1054(m), 855(s), 678(s), 404(m). Synthesis of [Cd3(pzta)2(μ-Cl)4(H2O)2]n (3): The reaction involved in situ ligand transformation of 2-Cyanopyrazine via cycloaddition reaction with the azide ion to give the 5(2-pyrazinyltetrazole) ligand. A mixture of CdCl2. H2O (0.201g; 1.0 mmol), H3PO4 (0.494 g, 5.0 mmol), 2-Cyanopyrazine (0.106 g; 2.0 mmol), NaN3 (0.65 g; 1.0 mmol) and H2O (15ml) sealed in a 20 ml Teflon-lined reactor was heated in an oven at 130°C for 36 h followed by cooling to room temperature at a rate of 10°C h-1 (Scheme 3). The resultant solution was allowed to evaporate slowly at room temperature for several weeks to give colorless crystals of 1 (yield: 69%). The resultant solution was allowed to evaporate slowly at room temperature for several weeks to give colourless crystals of 3 (yield: 69%). Elemental analysis for Cd3C10N10H12O2Cl4 (809.33): calcd. C, 14.84%; H, 1.24% and N, 20.76%; found: C, 14.36%; H, 1.23 and N, 20.72%. IR (KBr, cm-1): 3430(s), 2048(m), 1654(s), 1529(w), 1460(m), 1411(m), 1284(m), 1145(m), 1072(w), 1037(m), 870(m), 760(m),640(w), 528(w). Synthesis of CoH4N4C3O3 (4): The compound 4 was synthesized by the reaction of CoCl2.2H2O (0.356 g; 1.5 mmol), NaN3 (0.97 g; 1.5 mmol) and cyanoacetic acid (0.13 g; 1.5 mmol) in water under hydrothermal condition at 160oC for 24h (yield: 70%). The red
[82]
Chapter-2
precipitate obtained. Elemental analysis for CoH4N4C3O3 (202.99); calc. (%), C, 17.74%; H, 1.98% and N, 27.60% whereas found: C, 18.06%; H, 1.88 and N, 28.32%. IR (KBr, cm-1): 3360(m), 2902(w), 2343(m), 1661(m), 1573(s), 1388(s), 1146(w), 1065(m), 905(w), 588(m). Synthesis of CoH6N8C5O2 (5): The compound 5 was synthesized by the reaction of CoCl2.2H2O (0.71 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), acetylmalononitrile (0.32 g; 3.0 mmol) and ~15 mL water and ethanol under hydrothermal condition at 160oC for 24h, the pink precipitate obtained (yield: 76%). Elemental analysis for CoH6N8C5O2 (269.06); calc. (%): C, 22.31%; H, 2.24% and N, 37.01% whereas found: C, 22.00%; H, 2.12 and N, 36.56%. IR (KBr, cm-1): 3413(m), 2886(w), 1651(s), 1576(m), 1418(w), 1382(s), 1156(w), 1080(s), 1024(w), 893(w), 585(m). Synthesis of CoH4N6C4O2 (6): The compound 6 was synthesized by the reaction of CoCl2.2H2O (0.71 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), acetylmalononitrile (0.32 g; 3.0 mmol), cyanoacetic acid (0.25 g; 3.0 mmol), water (10mL) and ethanol (5mL) under hydrothermal condition at 110oC for 35h, the orange precipitate obtained (yield: 78%). Elemental analysis for CoH4N6C4O2 (227.02); calc.(%): C, 21.16%; H, 1.77% and N, 37.01% whereas found: C, 21.66%; H, 1.48 and N, 39.82%. IR (KBr, cm-1): 3429(m), 2222(s), 2096(s), 1626(w), 1534(s), 1427(w), 1388(s), 1335(w), 1037(s), 931(s). Synthesis of CoH3N3C3.5O2 (7): The compound 7 was synthesized by the reaction of CoCl2.2H2O (0.71 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), cyanoacetic acid (0.25 g; 3.0 mmol), 4-cyanobenzolic acid
(0.44 g; 3.0 mmol), water (10mL) and ethanol (5mL)
under hydrothermal condition at 110oC for 35h, the orange precipitate obtained (yield: 80%). Elemental analysis for CoH3N3C3.5O2 (177.99); calc. (%): C, 23.60%; H, 1.69%
[83]
Chapter-2
and N, 23.6% whereas found: C, 23.04%; H, 1.68 and N, 20.12%. IR (KBr, cm-1): 3376(m), 2202(s), 2091(s), 1679(s), 1520(s), 1427(w), 1030(w), 931(w), 771(w), 651(s). Synthesis of BaH4N4C3O3 (8): The compound 8 was synthesized by the reaction of Ba(O2CCH3)2 (0.77 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), cyanoacetic acid (0.25 g; 3.0 mmol), water (15mL) under hydrothermal condition at 110oC for 24h, the white precipitate obtained (yield: 79%). Elemental analysis for BaH4N4C3O3 (281.38); calc. (%): C, 12.80%; H, 1.43% and N, 19.91% whereas found: C, 13.04%; H, 1.48 and N, 20.12%. IR (KBr, cm-1): 3290(m), 2209(s), 2039(w), 1640(s), 1546(s), 1388(w), 1328(w), 1224(w), 1083(s), 1023(s), 804(s), 672(w). Synthesis of BaH5N8C5.5O3 (9): The compound 9 was synthesized by the reaction of CoCl2.2H2O (0.71 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), cyanoacetic acid (0.25 g; 3.0 mmol), acetylmalononitrile (0.32 g; 3.0 mmol), water (10mL) and ethanol (5mL) under hydrothermal condition at 110oC for 24h, the white precipitate obtained(yield: 75%). From the elemental analysis BaH5N8C5.5O3 (416.41); calc. (%): C, 15.86%; H, 1.21% and N, 26.91% whereas found: C, 15.74%; H, 1.38 and N, 27.12%. IR (KBr, cm-1): 3408(m), 2202(w), 2109(w), 1594(s), 1393(m), 1016(w), 420(s). Synthesis of MnH6N8C5O2 (10): The compound 10 was synthesized by a mixture of MnCl2.4H2O (0.59 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), acetylmalononitrile (0.32 g; 3.0 mmol), water (10mL) and ethanol (5mL) under hydrothermal condition at 160oC for 36h, the yellow precipitate obtained (yield: 80%). Elemental analysis for MnH6N8C5O2 (320.01) calc. (%): C, 22.65%; H, 2.28% and N, 42.27% whereas found: C, 22.74%; H, 2.18 and N, 41.12%. IR (KBr, cm-1): 3402(m), 2361(m), 2247(w), 1628(s), 1394(s), 1175(m), 1107(w), 1044(s), 642(m).
[84]
Chapter-2
Synthesis of CoH4N10C6O (11): The compound 11 was synthesized by a mixture of CoCl2.2H2O (0.71 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), 2,3- pyrazine dicarbonitrile (0.39 g; 3.0 mmol), water (10mL) and tetrahydrofuron(THF) (5mL) under hydrothermal condition at 110oC for 24h, the orange yellow was precipitate obtained (yield: 87%). From the elemental analysis CoH4N10C6O (350.02); calc. (%): C, 24.75%; H, 1.38% and N, 48.1%; found: C, 24.84%; H, 1.18 and N, 47.12%. IR (KBr, cm-1): 3157(m), 2348(s), 2072(m), 1708(s), 1602(w), 1377(s), 1169(s), 1095(w), 1057(s), 1019(s), 869(s), 793(s), 667(s), 536(m). Synthesis of SrH4N10C6O (12): The compound 12 was synthesized by a mixture of Sr(O2CCH3).1/2H2O (0.62 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), 2,3- pyrazine dicarbonitrile (0.39 g; 3.0 mmol), water (10mL) and tetrahydrofuron(THF) (5mL) under hydrothermal condition at 110oC for 24h, the orange precipitate obtained (yield: 84%). Elemental analysis for SrH4N10C6O (407.39); calc. (%): C, 22.53%; H, 1.2% and N, 43.80% whereas found: C, 21.84%; H, 1.18 and N, 43.12%. IR (KBr, cm-1): 3031(m), 2329(m), 2060(s), 1647(s), 1402(s), 1282(w), 1145(s), 1038(s), 937(m), 680(m). Synthesis of BaH4N10C6O (13): The compound 13 was synthesized by a mixture of Ba(O2CCH3)2 (0.77 g; 3.0 mmol), NaN3 (0.195 g; 3.0 mmol), 2,3- pyrazine dicarbonitrile (0.39 g; 3.0 mmol), water (10mL) and tetrahydrofuron (THF) (5mL) under hydrothermal condition at 110oC for 24h, the orange precipitate obtained (yield: 68%). Elemental analysis for BaH4N10C6O (506.81); calc. (%): C, 19.5%; H, 1.09% and N, 37.9%; found: C, 18.84%; H, 1.17 and N, 35.12%. IR (KBr, cm-1): 3414(m), 2348(m), 1628(s), 1501(m), 1402(m), 1282(w), 673(m), 561(s), 505(m).
[85]
Chapter-2
Table 6: Crystallographic data and processing parameters for Compound 1 Empirical formula
C10H10N12Na2O2 376.246 1
Mr/g mol−1 Compound
MoKα
Radiation Diffractometer
'Oxford XCalibur'
Crystal System Space group a(Å)
Triclinic P¯1 6.6586(5)
b(Å)
7.2459(6)
c(Å)
16.7473(10)
α(°) β(°)
88.455(6) 88.072(5)
γ(°) V(Å3)
76.940(6) 786.52(10)
Z
2 −3
Calc. density/g cm μ/mm−1
1.5887(2) 0.166
Absorption correction
'multi-scan'
Transmission factor range Refls. Measured
0.98359–1.00000 5293
Rint Mean σ(I)/I
0.0269 0.0575
R(Fobs)
0.0343
2
Rw(F )
0.0764
θ range Observed refls.
4.40–26.35 2161
[86]
Chapter-2
Table 7: All bond dimentions of the compound 1 Atom1 O1 O1 O1 O1 O2 O2 O2 N1 N1 N3 O2 O2 O2 O2 N7 N7 N7 N9 N9 N10 NA1 NA1 H11 NA1 NA1 NA1 NA2 NA2 H21 N2
Atom2 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 O1 O1 O1 O2 O2 O2 O2 O2 O2 C2
Atom3 O2 N1 N3 N5 N1 N3 N5 N3 N5 N5 N7 N9 N10 N4 N9 N10 N4 N10 N4 N4 H11 H12 H12 NA2 H21 H22 H21 H22 H22 H2
Angle 98.14 89.55 108.01 110.82 170.29 102.25 89.1 69.53 93.71 137.38 94.12 106.4 89.3 92.35 68.14 158.63 85.39 90.65 148.17 115.59 112.64 114.66 108.79 110.92 107.87 115.98 105.38 109.37 106.69 118.97
Atom1 NA1 NA1 C1 C2 NA1 NA1 N4 N3 N3 N5 N4 N4 N6 N5 NA2 NA2 C6 C7 NA2 NA2 N10 N9 N9 N11 N10 N11 N1 N1 H1 N2
[87]
Atom2 N1 N1 N1 N2 N3 N3 N3 N4 N4 N4 N5 N5 N5 N6 N7 N7 N7 N8 N9 N9 N9 N10 N10 N10 N11 N12 C1 C1 C1 C2
Atom3 Angle C1 129.45 C4 114.22 C4 116.12 C3 115.91 N4 139.74 C5 113.64 C5 104.81 N5 109.01 NA2 134.96 NA2 113.07 N6 109.5 NA1 129.35 NA1 110.19 C5 104.43 C6 126.99 C9 116.32 C9 116.03 C8 116.12 N10 140.38 C10 114.55 C10 104.36 N11 109.56 NA2 128.96 NA2 120.91 N12 109.28 C10 104.48 H1 118.87 C2 122.26 C2 118.87 C1 122.06 Cont…
Chapter-2
Atom1 C1 N2 N2 H3 N1 N1 C3 N3 N3 N6 N7 N7 H6 N8 N8 C6 N8 N8 H8 N7 N7 C8 N9 N9 N12 O1 O1 O1 O1 O2
Atom2 C2 C3 C3 C3 C4 C4 C4 C5 C5 C5 C6 C6 C6 C7 C7 C7 C8 C8 C8 C9 C9 C9 C10 C10 C10 NA1 NA1 NA1 NA1 NA1
Atom3 H2 H3 C4 C4 C3 C5 C5 N6 C4 C4 H6 C7 C7 C6 H7 H7 H8 C9 C9 C8 C10 C10 N12 C9 C9 O2 N1 N3 N5 N1
Angle 118.97 118.81 122.38 118.81 121.22 117.19 121.58 112.24 124.36 123.39 118.69 122.62 118.69 121.73 119.13 119.13 118.8 122.4 118.8 121.1 116.55 122.35 112.33 123.4 124.27 98.14 89.55 108.01 110.82 170.29
Atom1 O2 O2 N1 N1 N3 N10 N10 N10 N10 O2 O2 O2 N7 N7 N9 NA1 NA1 H11 NA1 NA1 NA1 NA2 NA2 H21 NA1 NA1 C1 C2 NA1 NA1
[88]
Atom2 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 O1 O1 O1 O2 O2 O2 O2 O2 O2 N1 N1 N1 N2 N3 N3
Atom3 Angle N3 102.25 N5 89.1 N3 69.53 N5 93.71 N5 137.38 O2 89.3 N7 158.63 N9 90.65 N4 115.59 N7 94.12 N9 106.4 N4 92.35 N9 68.14 N4 85.39 N4 148.17 H11 112.64 H12 114.66 H12 108.79 NA2 110.92 H21 107.87 H22 115.98 H21 105.38 H22 109.37 H22 106.69 C1 129.45 C4 114.22 C4 116.12 C3 115.91 N4 139.74 C5 113.64 Cont…
Chapter-2
Atom1 N4 N3 N3 N5 N4 N4 N6 N5 NA2 NA2 C6 C7 NA2 NA2 N10 NA2 NA2 N9 N10 N11 N1 N1 H1 N2 N2 C1 N2
Atom2 N3 N4 N4 N4 N5 N5 N5 N6 N7 N7 N7 N8 N9 N9 N9 N10 N10 N10 N11 N12 C1 C1 C1 C2 C2 C2 C3
Atom3 C5 N5 NA2 NA2 N6 NA1 NA1 C5 C6 C9 C9 C8 N10 C10 C10 N9 N11 N11 N12 C10 H1 C2 C2 C1 H2 H2 H3
Angle 104.81 109.01 134.96 113.07 109.5 129.35 110.19 104.43 126.99 116.32 116.03 116.12 140.38 114.55 104.36 128.96 120.91 109.56 109.28 104.48 118.87 122.26 118.87 122.06 118.97 118.97 118.81
Atom1 N1 C3 N3 N3 N6 N7 N7 H6 N8 N8 C6 N8 N8 H8 N7 N7 C8 N9 N9 N12 NA2 NA2 NA1 NA1 N2 H3 N1
[89]
Atom2 C4 C4 C5 C5 C5 C6 C6 C6 C7 C7 C7 C8 C8 C8 C9 C9 C9 C10 C10 C10 N4 N4 N5 N5 C3 C3 C4
Atom3 Angle C5 117.19 C5 121.58 N6 112.24 C4 124.36 C4 123.39 H6 118.69 C7 122.62 C7 118.69 C6 121.73 H7 119.13 H7 119.13 H8 118.8 C9 122.4 C9 118.8 C8 121.1 C10 116.55 C10 122.35 N12 112.33 C9 123.4 C9 124.27 N5 113.07 N5 113.07 N4 129.35 N4 129.35 C4 122.38 C4 118.81 C3 121.22 Cont…
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
O2 O2 N1 N1 N3 N3 N5 N5 O1 O1 O1 N1 N1 N1 N3 N3 N3 N5 N5 N5 O1 O1 O2 O2 N3 N3 N5 N5 O1 O1
NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1
O1 O1 O1 O1 O1 O1 O1 O1 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 N1 N1 N1 N1 N1 N1 N1 N1 N3 N3
H11 H12 H11 H12 H11 H12 H11 H12 NA2 H21 H22 NA2 H21 H22 NA2 H21 H22 NA2 H21 H22 C1 C4 C1 C4 C1 C4 C1 C4 N4 C5
5.43 130.56 -168.6 -43.5 -100.4 24.78 97.58 -137.3 96.21 -18.73 -138.3 -121.7 123.39 3.87 -153.3 91.8 -27.72 -14.69 -129.6 110.85 -71.66 102.83 145.78 -39.74 178.89 -6.62 39.17 -146.3 87.67 -73.87
O2 O2 N1 N1 N5 N5 O1 O2 N1 N3 N7 N7 N7 N9 N9 N9 N10 N10 N10 N4 N4 N4 O2 O2 N9 N9 N10 N10 N4 N4
NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2
N3 N3 N3 N3 N3 N3 N5 N5 N5 N5 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 N7 N7 N7 N7 N7 N7 N7 N7
N4 C5 N4 C5 N4 C5 N4 N4 N4 N4 NA1 H21 H22 NA1 H21 H22 NA1 H21 H22 NA1 H21 H22 C6 C9 C6 C9 C6 C9 C6 C9
-15.22 -176.8 170.19 8.65 -117.5 80.99 -71.49 26.88 -162.4 134.13 -76.95 39.53 153.89 -145.4 -28.88 85.47 124.17 -119.4 -4.99 8.59 125.07 -120.6 73.07 -97.19 179.1 8.83 171.74 1.48 -18.95 170.78 Cont…
[90]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
O2 O2 N7 N7 N10 N10 N4 N4 O2 O2 N7 N7 N9 N9 N4 N4 O2 N7 N9 N10 NA1 NA1 C4 C4 NA1 NA1 C1 C1 C3 C3
NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 N1 N1 N1 N1 N1 N1 N1 N1 N2 N2
N9 N9 N9 N9 N9 N9 N9 N9 N10 N10 N10 N10 N10 N10 N10 N10 N4 N4 N4 N4 C1 C1 C1 C1 C4 C4 C4 C4 C2 C2
N10 C10 N10 C10 N10 C10 N10 C10 N9 N11 N9 N11 N9 N11 N9 N11 N5 N5 N5 N5 H1 C2 H1 C2 C3 C5 C3 C5 C1 H2
-88.07 80.29 -175.9 -7.57 1.4 169.76 148.22 -43.42 105.25 -84.45 5.68 175.98 -1.14 169.16 -162.5 7.82 7.33 101.28 134.32 -83.02 -7.35 172.65 178.25 -1.75 -175.5 3.94 -0.22 179.2 -0.19 179.81
C2 C2 NA1 NA1 C5 C5 NA1 NA1 N4 N4 N3 N3 NA2 NA2 N4 NA1 N5 N5 NA2 NA2 C9 C9 NA2 NA2 C6 C6 C8 C8 C7 C7
N2 N2 N3 N3 N3 N3 N3 N3 N3 N3 N4 N4 N4 N4 N5 N5 N6 N6 N7 N7 N7 N7 N7 N7 N7 N7 N8 N8 N8 N8
C3 C3 N4 N4 N4 N4 C5 C5 C5 C5 N5 N5 N5 N5 N6 N6 C5 C5 C6 C6 C6 C6 C9 C9 C9 C9 C7 C7 C8 C8
H3 C4 N5 NA2 N5 NA2 N6 C4 N6 C4 N6 NA1 N6 NA1 C5 C5 N3 C4 H6 C7 H6 C7 C8 C10 C8 C10 C6 H7 H8 C9
178.22 -1.78 -162.4 -4.03 0.12 158.51 167.78 -11.02 0 -178.8 -0.2 139.61 -163.8 -23.94 0.19 -147.7 -0.12 178.7 10.13 -169.9 -179.6 0.42 170.88 -9.04 -0.47 179.6 -0.22 179.78 -179.8 0.16
Cont…
[91]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
NA2 NA2 C10 C10 NA2 NA2 N10 N10 N9 NA2 N9 N9 N9 N9 N11 N11 N11 N11 N10 N11 N11 N1 N1 H1 H1 N2 N2 H3 H3 N1
N9 N9 N9 N9 N9 N9 N9 N9 N10 N10 N10 N10 N10 N10 N10 N10 N10 N10 N11 N12 N12 C1 C1 C1 C1 C3 C3 C3 C3 C4
N10 N10 N10 N10 C10 C10 C10 C10 N11 N11 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 N12 C10 C10 C2 C2 C2 C2 C4 C4 C4 C4 C5
N11 NA2 N11 NA2 N12 C9 N12 C9 N12 N12 O2 N7 N9 N4 O2 N7 N9 N4 C10 N9 C9 N2 H2 N2 H2 N1 C5 N1 C5 N3
169.38 -1.79 0.3 -170.9 -172.7 6.53 -0.34 178.9 -0.16 171.85 -105.3 -5.68 1.14 162.48 84.45 -176 -169.2 -7.82 -0.05 0.25 -179 2.05 -178 -178 2.05 2.07 -177.3 -177.9 2.68 4.86
N1 C3 C3 N7 N7 H6 H6 N8 N8 H8 H8 N7 N7 C8 C8 O2 O2 N1 N1 N3 N3 N5 N5 O1 O1 O1 N1 N1 N1 N3
C4 C4 C4 C6 C6 C6 C6 C8 C8 C8 C8 C9 C9 C9 C9 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1
C5 C5 C5 C7 C7 C7 C7 C9 C9 C9 C9 C10 C10 C10 C10 O1 O1 O1 O1 O1 O1 O1 O1 O2 O2 O2 O2 O2 O2 O2
N6 N3 N6 N8 H7 N8 H7 N7 C10 N7 C10 N9 N12 N9 N12 H11 H12 H11 H12 H11 H12 H11 H12 NA2 H21 H22 NA2 H21 H22 NA2
-173.8 -175.7 5.6 -0.07 179.93 179.93 -0.07 0.2 -179.9 -179.8 0.12 1.76 -179.1 -178.2 0.99 -5.43 -130.6 168.62 43.5 100.35 -24.78 -97.58 137.3 -96.21 18.73 138.25 121.67 -123.4 -3.87 153.26
Cont…
[92]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
N3 N3 N5 N5 N5 O1 O1 O2 O2 N3 N3 N5 N5 O1 O1 O2 O2 N1 N1 N5 N5 O1 O2 N1 N3 N10 N10 N10 N7 N7
NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 NA2
O2 O2 O2 O2 O2 N1 N1 N1 N1 N1 N1 N1 N1 N3 N3 N3 N3 N3 N3 N3 N3 N5 N5 N5 N5 O2 O2 O2 O2 O2
H21 H22 NA2 H21 H22 C1 C4 C1 C4 C1 C4 C1 C4 N4 C5 N4 C5 N4 C5 N4 C5 N4 N4 N4 N4 NA1 H21 H22 NA1 H21
-91.8 27.72 14.69 129.63 -110.9 71.66 -102.8 -145.8 39.74 -178.9 6.62 -39.17 146.34 -87.67 73.87 15.22 176.76 -170.2 -8.65 117.47 -80.99 71.49 -26.88 162.42 -134.1 -124.2 119.35 4.99 76.95 -39.53
N7 N9 N9 N9 N4 N4 N4 N10 N10 O2 O2 N9 N9 N4 N4 N10 N10 O2 O2 N7 N7 N4 N4 N10 O2 N7 N9 NA1 NA1 C4
NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 NA2 N1 N1 N1
O2 O2 O2 O2 O2 O2 O2 N7 N7 N7 N7 N7 N7 N7 N7 N9 N9 N9 N9 N9 N9 N9 N9 N4 N4 N4 N4 C1 C1 C1
H22 NA1 H21 H22 NA1 H21 H22 C6 C9 C6 C9 C6 C9 C6 C9 N10 C10 N10 C10 N10 C10 N10 C10 N5 N5 N5 N5 H1 C2 H1
-153.9 145.36 28.88 -85.47 -8.59 -125.1 120.57 -171.7 -1.48 -73.07 97.19 -179.1 -8.83 18.95 -170.8 -1.4 -169.8 88.07 -80.29 175.93 7.57 -148.2 43.42 83.02 -7.33 -101.3 -134.3 7.35 -172.7 -178.3 Cont…
[93]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
C4 NA1 NA1 C1 C1 C3 C3 C2 C2 NA1 NA1 C5 C5 NA1 NA1 N4 N4 N3 N3 NA2 NA2 N4 NA1 N5 N5 NA2 NA2 C9 C9 N1
N1 N1 N1 N1 N1 N2 N2 N2 N2 N3 N3 N3 N3 N3 N3 N3 N3 N4 N4 N4 N4 N5 N5 N6 N6 N7 N7 N7 N7 C4
C1 C4 C4 C4 C4 C2 C2 C3 C3 N4 N4 N4 N4 C5 C5 C5 C5 N5 N5 N5 N5 N6 N6 C5 C5 C6 C6 C6 C6 C5
C2 C3 C5 C3 C5 C1 H2 H3 C4 N5 NA2 N5 NA2 N6 C4 N6 C4 N6 NA1 N6 NA1 C5 C5 N3 C4 H6 C7 H6 C7 N6
1.75 175.48 -3.94 0.22 -179.2 0.19 -179.8 -178.2 1.78 162.43 4.03 -0.12 -158.5 -167.8 11.02 0 178.8 0.2 -139.6 163.75 23.94 -0.19 147.69 0.12 -178.7 -10.13 169.87 179.58 -0.42 173.81
NA2 NA2 C6 C6 C8 C8 C7 C7 NA2 NA2 C10 C10 NA2 NA2 N10 N10 NA2 N9 N10 N11 N11 N1 N1 H1 H1 N2 N2 H3 H3 N1
N7 N7 N7 N7 N8 N8 N8 N8 N9 N9 N9 N9 N9 N9 N9 N9 N10 N10 N11 N12 N12 C1 C1 C1 C1 C3 C3 C3 C3 C4
C9 C9 C9 C9 C7 C7 C8 C8 N10 N10 N10 N10 C10 C10 C10 C10 N11 N11 N12 C10 C10 C2 C2 C2 C2 C4 C4 C4 C4 C5
C8 C10 C8 C10 C6 H7 H8 C9 NA2 N11 NA2 N11 N12 C9 N12 C9 N12 N12 C10 N9 C9 N2 H2 N2 H2 N1 C5 N1 C5 N3
-170.9 9.04 0.47 -179.6 0.22 -179.8 179.84 -0.16 1.79 -169.4 170.88 -0.3 172.71 -6.53 0.34 -178.9 -171.9 0.16 0.05 -0.25 178.98 -2.05 177.95 177.95 -2.05 -2.07 177.32 177.93 -2.68 -4.86 Cont…
[94]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
C3 C3 N7 N7 H6 H6 N8 NA2
C4 C4 C6 C6 C6 C6 C8 N4
C5 C5 C7 C7 C7 C7 C9 N5
N3 N6 N8 H7 N8 H7 N7 NA1
175.73 -5.6 0.07 -179.9 -179.9 0.07 -0.2 23.94
N8 H8 H8 N7 N7 C8 C8 NA2
C8 C8 C8 C9 C9 C9 C9 N4
C9 C9 C9 C10 C10 C10 C10 N5
C10 N7 C10 N9 N12 N9 N12 NA1
179.88 179.8 -0.12 -1.76 179.09 178.16 -0.99 -23.94
Atom1 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 NA2 O1 O1 O2 O2 N1 N1 N2 N2
Atom2 O1 O2 N1 N3 N5 O2 N7 N9 N10 N4 H11 H12 H21 H22 C1 C4 C2 C3
Length 2.3289(2) 2.3495(1) 2.5323(2) 2.4352(2) 2.3992(2) 2.4260(2) 2.5218(2) 2.4832(2) 2.4058(2) 2.4797(1) 0.8805(1) 0.7810(1) 0.9190(1) 0.8232(1) 1.3377(1) 1.3384(1) 1.3360(1) 1.3323(1)
Atom1 N3 N3 N4 N4 N5 N5 N6 N7 N7 N8 N8 N9 N9 N10 N10 N11 N12 C1
Atom2 N4 C5 N5 NA2 N6 NA1 C5 C6 C9 C7 C8 N10 C10 N11 NA2 N12 C10 H1
Length 1.3465(1) 1.3333(1) 1.3239(1) 2.4797(1) 1.3488(1) 2.3992(2) 1.3323(1) 1.3334(1) 1.3457(1) 1.3347(1) 1.3360(1) 1.3496(1) 1.3351(1) 1.3154(1) 2.4058(2) 1.3534(1) 1.3304(1) 0.9500(1)
Cont…
[95]
Chapter-2
Atom1 C1 C2 C3 C3 C4 C6 C6 C7 C8 C8 C9 NA1 NA1 NA1 NA1 NA1 NA2 NA2 NA2 NA2 O1 O1 O2 O2 N1 N1 N2 N2 N3
Atom2 C2 H2 H3 C4 C5 H6 C7 H7 H8 C9 C10 O1 O2 N1 N3 N5 O2 N7 N9 N4 H11 H12 H21 H22 C1 C4 C2 C3 N4
Length 1.3777(1) 0.9500(1) 0.9500(1) 1.3935(1) 1.4665(1) 0.9500(1) 1.3759(1) 0.9500(1) 0.9500(1) 1.3858(1) 1.4658(1) 2.3289(2) 2.3495(1) 2.5323(2) 2.4352(2) 2.3992(2) 2.4260(2) 2.5218(2) 2.4832(2) 2.4797(1) 0.8805(1) 0.7810(1) 0.9190(1) 0.8232(1) 1.3377(1) 1.3384(1) 1.3360(1) 1.3323(1) 1.3465(1)
Atom1 N3 N4 N4 N5 N5 N6 N7 N7 N8 N8 N9 N9 N10 N11 N12 C1 C1 C2 C3 C3 C4 C6 C6 C7 C8 C8 C9 N4 N4
[96]
Atom2 C5 N5 NA2 N6 NA1 C5 C6 C9 C7 C8 N10 C10 N11 N12 C10 H1 C2 H2 H3 C4 C5 H6 C7 H7 H8 C9 C10 N5 N5
Length 1.3333(1) 1.3239(1) 2.4797(1) 1.3488(1) 2.3992(2) 1.3323(1) 1.3334(1) 1.3457(1) 1.3347(1) 1.3360(1) 1.3496(1) 1.3351(1) 1.3154(1) 1.3534(1) 1.3304(1) 0.9500(1) 1.3777(1) 0.9500(1) 0.9500(1) 1.3935(1) 1.4665(1) 0.9500(1) 1.3759(1) 0.9500(1) 0.9500(1) 1.3858(1) 1.4658(1) 1.3239(1) 1.3239(1)
Chapter-2
Table 8: Crystallographic data and processing parameters for Compound 2
Empirical formula
C10H10N12O2Zn 395.67 2 MoKα 'Oxford XCalibur' Monoclinic P 2 1/n 6.0910(6) 11.4576(12) 10.6860(11) 90.00 105.626(2) 90.00 718.194 2 1.980 2.123 'multi-scan' 0.99859-1.00000 1629 0.0473 0.1123 2.66-27.86 2311
−1
Mr/g mol Compound Radiation Diffractometer Crystal System Space group a(Å) b(Å) c(Å) α(°) β(°) γ(°) V(Å3) Z Calc. density/g cm−3 μ/mm−1 Absorption correction Transmission factor range Refls. Measured Rint Mean σ(I)/I θ range Observed refls.
[97]
Chapter-2
Table 9: All angles and bond lengths of the compound 2 Atom1 Atom2 Atom3 Angle O1W Zn1 N1 89.88(7) O1W Zn1 N3 87.65(7) O1W Zn1 O1W 180.00(7) O1W Zn1 N1 90.12(7) O1W Zn1 N3 92.35(7) N1 Zn1 N3 78.52(6) N1 Zn1 O1W 90.12(7) N1 Zn1 N1 180.00(6) N1 Zn1 N3 101.48(6) N3 Zn1 O1W 92.35(7) N3 Zn1 N1 101.48(6) N3 Zn1 N3 180.00(7) O1W Zn1 N1 89.88(7) O1W Zn1 N3 87.65(7) N1 Zn1 N3 78.52(6) Zn1 O1W H1W1 116(2) Zn1 O1W H1W2 119(2) H1W1 O1W H1W2 115(2) Zn1 N1 C1 130.8(1) Zn1 N1 C4 112.3(1) C1 N1 C4 116.9(2) C2 N2 C3 116.2(2) Zn1 N3 N4 142.4(1) Zn1 N3 C5 112.3(1) N4 N3 C5 105.0(2) N3 N4 N5 109.0(2) N4 N5 N6 109.5(2) N5 N6 C5 105.1(2) N1 C1 C2 121.5(2) N2 C2 C1 122.1(2)
Atom1 Atom2 Atom3 Angle N1 C1 H1 117(1) C2 C1 H1 121(1) N2 C2 C1 122.1(2) N2 C2 H2 117(1) C1 C2 H2 121(1) N2 C3 C4 122.4(2) N2 C3 H3 119(1) C4 C3 H3 119(1) N1 C4 C3 120.8(2) N1 C4 C5 115.8(2) C3 C4 C5 123.4(2) N3 C5 N6 111.4(2) N3 C5 C4 121.0(2) N6 C5 C4 127.6(2) Zn1 O1W H1W1 116(2) Zn1 O1W H1W2 119(2) H1W1 O1W H1W2 115(2) Zn1 N1 C1 130.8(1) Zn1 N1 C4 112.3(1) C1 N1 C4 116.9(2) C2 N2 C3 116.2(2) Zn1 N3 N4 142.4(1) Zn1 N3 C5 112.3(1) N4 N3 C5 105.0(2) N3 N4 N5 109.0(2) N4 N5 N6 109.5(2) N5 N6 C5 105.1(2) N1 C1 C2 121.5(2) N1 C1 H1 117(1) C2 C1 H1 121(1) Cont…
[98]
Chapter-2
Atom1 Atom2 Atom3 Angle N2 C2 H2 117(1) C1 C2 H2 121(1) N2 C3 C4 122.4(2) N2 C3 H3 119(1) C4 C3 H3 119(1)
Atom1 Atom2 Atom3 Angle N1 C4 C3 120.8(2) N1 C4 C5 115.8(2) C3 C4 C5 123.4(2) N3 C5 N6 111.4(2) N3 C5 C4 121.0(2) N6 C5 C4 127.6(2)
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
N1
Zn1
O1W
H1W1
-43(2)
N3
Zn1
N1
C4
-178.9(1)
N1
Zn1
O1W
H1W2
173(2)
O1W
Zn1
N3
N4
-84.6(2)
N3
Zn1
O1W
H1W1
-122(2)
O1W
Zn1
N3
C5
87.8(1)
N3
Zn1
O1W
H1W2
94(2)
N1
Zn1
N3
N4
-174.9(2)
O1W
Zn1
O1W
H1W1
Undefined
N1
Zn1
N3
C5
-2.6(1)
O1W
Zn1
O1W
H1W2
Undefined
O1W
Zn1
N3
N4
95.4(2)
N1
Zn1
O1W
H1W1
137(2)
O1W
Zn1
N3
C5
-92.2(1)
N1
Zn1
O1W
H1W2
-7(2)
N1
Zn1
N3
N4
5.1(2)
N3
Zn1
O1W
H1W1
58(2)
N1
Zn1
N3
C5
177.4(1)
N3
Zn1
O1W
H1W2
-86(2)
N3
Zn1
N3
N4
Undefined
O1W
Zn1
N1
C1
94.4(2)
N3
Zn1
N3
C5
Undefined
O1W
Zn1
N1
C4
-86.6(1)
O1W
Zn1
O1W
H1W1
Undefined
N3
Zn1
N1
C1
-177.9(2)
O1W
Zn1
O1W
H1W2
Undefined
N3
Zn1
N1
C4
1.1(1)
N1
Zn1
O1W
H1W1
-137(2)
O1W
Zn1
N1
C1
-85.6(2)
N1
Zn1
O1W
H1W2
7(2)
O1W
Zn1
N1
C4
93.4(1)
N3
Zn1
O1W
H1W1
-58(2)
N1
Zn1
N1
C1
Undefined
N3
Zn1
O1W
H1W2
86(2)
N1
Zn1
N1
C4
Undefined
N1
Zn1
O1W
H1W1
43(2)
N3
Zn1
N1
C1
2.1(2)
N1
Zn1
O1W
H1W2
-173(2)
N3
Zn1
O1W
H1W2
-94(2)
N3
Zn1
O1W
H1W1
122(2)
O1W
Zn1
N1
C1
85.6(2)
N3
Zn1
N1
C4
178.9(1)
O1W
Zn1
N1
C4
-93.4(1)
O1W
Zn1
N1
C1
-94.4(2)
N1
Zn1
N1
C1
Undefined
O1W
Zn1
N1
C4
86.6(1)
N1
Zn1
N1
C4
Undefined
N3
Zn1
N1
C1
177.9(2)
N3
Zn1
N1
C1
-2.1(2)
N3
Zn1
N1
C4
-1.1(1)
Cont…
[99]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
O1W
Zn1
N3
N4
-95.4(2)
Zn1
N3
C5
N6
-175.4(1)
O1W
Zn1
N3
C5
92.2(1)
Zn1
N3
C5
C4
4.0(2)
N1
Zn1
N3
N4
-5.1(2)
N4
N3
C5
N6
-0.2(2)
N1
Zn1
N3
C5
-177.4(1)
N4
N3
C5
C4
179.1(2)
N3
Zn1
N3
N4
Undefined
N3
N4
N5
N6
0.2(2)
N3
Zn1
N3
C5
Undefined
N4
N5
N6
C5
-0.4(2)
O1W
Zn1
N3
N4
84.6(2)
N5
N6
C5
N3
0.4(2)
O1W
Zn1
N3
C5
-87.8(1)
N5
N6
C5
C4
-178.9(2)
N1
Zn1
N3
N4
174.9(2)
N1
C1
C2
N2
0.1(4)
N1
Zn1
N3
C5
2.6(1)
N1
C1
C2
H2
177(1)
Zn1
N1
C1
C2
179.1(2)
H1
C1
C2
N2
180(1)
Zn1
N1
C1
H1
-0(1)
H1
C1
C2
H2
-4(2)
C4
N1
C1
C2
0.2(3)
N2
C3
C4
N1
-0.1(3)
C4
N1
C1
H1
-179(1)
N2
C3
C4
C5
-180.0(2)
Zn1
N1
C4
C3
-179.3(2)
H3
C3
C4
N1
-180(1)
Zn1
N1
C4
C5
0.6(2)
H3
C3
C4
C5
0(1)
C1
N1
C4
C3
-0.2(3)
N1
C4
C5
N3
-3.1(3)
C1
N1
C4
C5
179.7(2)
N1
C4
C5
N6
176.1(2)
C3
N2
C2
C1
-0.4(3)
C3
C4
C5
N3
176.7(2)
C3
N2
C2
H2
-177(1)
C3
C4
C5
N6
-4.1(3)
C2
N2
C3
C4
0.4(3)
Zn1
N1
C1
C2
-179.1(2)
C2
N2
C3
H3
-180(1)
Zn1
N1
C1
H1
0(1)
Zn1
N3
N4
N5
172.6(2)
C4
N1
C1
C2
-0.2(3)
C5
N3
N4
N5
0.0(2)
C4
N1
C1
H1
179(1)
C3
N2
C2
C1
0.4(3)
Zn1
N1
C4
C3
179.3(2)
C3
N2
C2
H2
177(1)
Zn1
N1
C4
C5
-0.6(2)
C2
N2
C3
C4
-0.4(3)
C1
N1
C4
C3
0.2(3)
C2
N2
C3
H3
180(1)
C1
N1
C4
C5
-179.7(2)
Cont…
[100]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
Zn1
N3
N4
N5
-172.6(2)
N1
C1
C2
H2
-177(1)
C5
N3
N4
N5
-0.0(2)
H1
C1
C2
N2
-180(1)
Zn1
N3
C5
N6
175.4(1)
H1
C1
C2
H2
4(2)
Zn1
N3
C5
C4
-4.0(2)
N2
C3
C4
N1
0.1(3)
N4
N3
C5
N6
0.2(2)
N2
C3
C4
C5
180.0(2)
N4
N3
C5
C4
-179.1(2)
H3
C3
C4
N1
180(1)
N3
N4
N5
N6
-0.2(2)
H3
C3
C4
C5
-0(1)
N4
N5
N6
C5
0.4(2)
N1
C4
C5
N3
3.1(3)
N5
N6
C5
N3
-0.4(2)
N1
C4
C5
N6
-176.1(2)
N5
N6
C5
C4
178.9(2)
C3
C4
C5
N3
-176.7(2)
N1
C1
C2
N2
-0.1(4)
C3
C4
C5
N6
4.1(3)
Atom2 O1W N1 N3 O1W N1 N3 H1W1 H1W2 C1 C4 C2 C3 N4 C5 N5 N5 N6 C5 C2 H1
Length 2.102(2) 2.197(2) 2.117(2) 2.102(2) 2.197(2) 2.117(2) 0.84(2) 0.85(2) 1.331(3) 1.340(2) 1.328(3) 1.329(3) 1.336(2) 1.334(3) 1.312(3) 1.312(3) 1.336(3) 1.322(2) 1.382(3) 0.95(2)
Atom1 Zn1 Zn1 Zn1 Zn1 Zn1 Zn1 O1W O1W N1 N1 N2 N2 N3 N3 N4 N4 N5 N6 C1 C1
Atom1 N5 N6 C1 C1 C2 C3 C3 C4 O1W O1W N1 N1 N2 N2 N3 N3 C2 C3 C3 C4
[101]
Atom2 N6 C5 C2 H1 H2 C4 H3 C5 H1W1 H1W2 C1 C4 C2 C3 N4 C5 H2 C4 H3 C5
Length 1.336(3) 1.322(2) 1.382(3) 0.95(2) 0.95(1) 1.384(3) 0.95(2) 1.460(2) 0.84(2) 0.85(2) 1.331(3) 1.340(2) 1.328(3) 1.329(3) 1.336(2) 1.334(3) 0.95(1) 1.384(3) 0.95(2) 1.460(2)
Chapter-2
Table 10: Crystallographic data and processing parameters for Compound 3 Empirical formula
C10H10Cd3Cl4N12O2
Mr/g mol−1
809.33
Compound
3
Radiation
MoKα
Diffractometer
'Oxford XCalibur'
Crystal System
Triclinic
Space group
P -1
a(Å)
6.9657(4)
b(Å)
7.5934(5)
c(Å)
11.0040(7)
α(°)
101.339(5)
β(°)
96.824(5)
γ(°)
109.725(6)
V(Å3)
526.269
Z
1
ρcalc. mg/mm3
2.554
−1
μ/mm
3.548 ‘multi-scan’
Absorption correction F(000)
382
Refls. Measured
3409
Final R indexes [all data]
R1 = 0.0174, wR2 = 0.0426
Goodness-of-fit on F2
1.052
θ range
4.22-26.31
Observed refls.
2129
[102]
Chapter-2
Table 11: All angles and bond lengths of the compound 3 Atom1 Atom2 Atom3 Angle Cl1 Cd1 N1 84.29(5) Cl1 Cd1 Cl1 180.00(2) Cl1 Cd1 N1 95.71(5) Cl1 Cd1 Cl2 86.42(2) Cl1 Cd1 Cl2 93.58(2) N1 Cd1 Cl1 95.71(5) N1 Cd1 N1 180.00(7) N1 Cd1 Cl2 90.75(5) N1 Cd1 Cl2 89.25(5) Cl1 Cd1 N1 84.29(5) Cl1 Cd1 Cl2 93.58(2) Cl1 Cd1 Cl2 86.42(2) N1 Cd1 Cl2 89.25(5) N1 Cd1 Cl2 90.75(5) Cl2 Cd1 Cl2 180.00(2) Cl2 Cd2 O1 175.42(5) Cl2 Cd2 N2 92.07(5) Cl2 Cd2 N3 89.18(5) Cl2 Cd2 Cl1 87.38(2) Cl2 Cd2 N4 92.75(5) O1 Cd2 N2 83.96(7) O1 Cd2 N3 91.60(6) O1 Cd2 Cl1 90.38(5) O1 Cd2 N4 91.67(7) N2 Cd2 N3 70.09(7) N2 Cd2 Cl1 90.60(5) N2 Cd2 N4 164.31(7) N3 Cd2 Cl1 160.25(5) N3 Cd2 N4 95.05(7) Cl1 Cd2 N4 104.53(5)
Atom1 Atom2 Atom3 Angle Cd1 Cl1 Cd2 93.62(2) Cd2 Cl2 Cd1 92.23(2) Cd2 O1 H11 111(2) Cd2 O1 H12 121(4) Cd2 O1 H13 113(3) H11 O1 H12 102(4) H11 O1 H13 118(4) H12 O1 H13 91(5) Cd1 N1 C1 121.6(2) Cd1 N1 C4 121.1(2) C1 N1 C4 117.1(2) Cd2 N2 C2 126.4(2) Cd2 N2 C3 116.2(1) C2 N2 C3 117.2(2) Cd2 N3 N4 140.0(1) Cd2 N3 C5 115.4(1) N4 N3 C5 104.4(2) N3 N4 N5 110.1(2) N3 N4 Cd2 124.8(1) N5 N4 Cd2 125.1(2) N4 N5 N6 108.5(2) N5 N6 C5 105.4(2) N1 C1 H1 119.3(2) N1 C1 C2 121.4(2) H1 C1 C2 119.3(2) N2 C2 C1 121.5(2) N2 C2 H2 119.2(2) C1 C2 H2 119.3(2) N2 C3 C4 121.3(2) N2 C3 C5 115.4(2) Cont…
[103]
Chapter-2
Atom1 Atom2 Atom3 Angle C4 C3 C5 123.2(2) N1 C4 C3 121.4(2) N1 C4 H4 119.3(2) C3 C4 H4 119.3(2) N3 C5 N6 111.6(2) N3 C5 C3 121.8(2) N6 C5 C3 126.5(2) Cl2 Cd2 O1 175.42(5) Cl2 Cd2 N2 92.07(5) Cl2 Cd2 N3 89.18(5) Cl2 Cd2 Cl1 87.38(2) Cl2 Cd2 N4 92.75(5) O1 Cd2 N2 83.96(7) O1 Cd2 N3 91.60(6) O1 Cd2 Cl1 90.38(5) O1 Cd2 N4 91.67(7) N2 Cd2 N3 70.09(7) N2 Cd2 Cl1 90.60(5) N2 Cd2 N4 164.31(7) N3 Cd2 Cl1 160.25(5) N3 Cd2 N4 95.05(7) Cl1 Cd2 N4 104.53(5) Cd1 Cl1 Cd2 93.62(2) Cd2 Cl2 Cd1 92.23(2) Cd2 O1 H11 111(2) Cd2 O1 H12 121(4) Cd2 O1 H13 113(3) H11 O1 H12 102(4) H11 O1 H13 118(4) H12 O1 H13 91(5) Cd1 N1 C1 121.6(2) Cd2 Cl1 Cd1 93.62(2) Cd1 Cl2 Cd2 92.23(2) Cd1 Cl2 Cd2 92.23(2)
Atom1 Atom2 Atom3 Angle Cd1 N1 C4 121.1(2) C1 N1 C4 117.1(2) Cd2 N2 C2 126.4(2) Cd2 N2 C3 116.2(1) C2 N2 C3 117.2(2) Cd2 N3 N4 140.0(1) Cd2 N3 C5 115.4(1) N4 N3 C5 104.4(2) N3 N4 N5 110.1(2) N3 N4 Cd2 124.8(1) N5 N4 Cd2 125.1(2) N4 N5 N6 108.5(2) N5 N6 C5 105.4(2) N1 C1 H1 119.3(2) N1 C1 C2 121.4(2) H1 C1 C2 119.3(2) N2 C2 C1 121.5(2) N2 C2 H2 119.2(2) C1 C2 H2 119.3(2) N2 C3 C4 121.3(2) N2 C3 C5 115.4(2) C4 C3 C5 123.2(2) N1 C4 C3 121.4(2) N1 C4 H4 119.3(2) C3 C4 H4 119.3(2) N3 C5 N6 111.6(2) N3 C5 C3 121.8(2) N6 C5 C3 126.5(2) Cl2 Cd1 Cl1 86.42(2) Cl2 Cd1 Cl1 86.42(2) Cl1 Cd2 Cl2 87.38(2) Cl1 Cd2 Cl2 87.38(2) Cd2 Cl1 Cd1 93.62(2)
[104]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
N1
Cd1
Cl1
Cd2
-95.70(5)
Cl1
Cd1
Cl2
Cd2
4.43(2)
Cl1
Cd1
Cl1
Cd2
Undefined
N1
Cd1
Cl2
Cd2
88.66(5)
N1
Cd1
Cl1
Cd2
84.30(5)
Cl1
Cd1
Cl2
Cd2
-175.57(2)
Cl2
Cd1
Cl1
Cd2
-4.58(2)
N1
Cd1
Cl2
Cd2
-91.34(5)
Cl2
Cd1
Cl1
Cd2
175.42(2)
Cl2
Cd1
Cl2
Cd2
Undefined
Cl1
Cd1
N1
C1
-79.7(2)
Cl1
Cd1
Cl2
Cd2
175.57(2)
Cl1
Cd1
N1
C4
95.2(2)
N1
Cd1
Cl2
Cd2
91.34(5)
Cl1
Cd1
N1
C1
100.3(2)
Cl1
Cd1
Cl2
Cd2
-4.43(2)
Cl1
Cd1
N1
C4
-84.8(2)
N1
Cd1
Cl2
Cd2
-88.66(5)
N1
Cd1
N1
C1
Undefined
Cl2
Cd1
Cl2
Cd2
Undefined
N1
Cd1
N1
C4
Undefined
O1
Cd2
Cl2
Cd1
56.2(6)
Cl2
Cd1
N1
C1
-166.0(2)
N2
Cd2
Cl2
Cd1
85.95(5)
Cl2
Cd1
N1
C4
8.9(2)
N3
Cd2
Cl2
Cd1
155.99(5)
Cl2
Cd1
N1
C1
14.0(2)
Cl1
Cd2
Cl2
Cd1
-4.56(2)
Cl2
Cd1
N1
C4
-171.1(2)
N4
Cd2
Cl2
Cd1
-108.99(5)
Cl1
Cd1
Cl1
Cd2
Undefined
Cl2
Cd2
O1
H11
-133(2)
N1
Cd1
Cl1
Cd2
-84.30(5)
Cl2
Cd2
O1
H12
107(5)
N1
Cd1
Cl1
Cd2
95.70(5)
Cl2
Cd2
O1
H13
2(4)
Cl2
Cd1
Cl1
Cd2
-175.42(2)
N2
Cd2
O1
H11
-163(2)
Cl2
Cd1
Cl1
Cd2
4.58(2)
N2
Cd2
O1
H12
77(5)
Cl1
Cd1
N1
C1
-100.3(2)
N2
Cd2
O1
H13
-28(4)
Cl1
Cd1
N1
C4
84.8(2)
N3
Cd2
O1
H11
127(2)
N1
Cd1
N1
C1
Undefined
N3
Cd2
O1
H12
8(5)
N1
Cd1
N1
C4
Undefined
N3
Cd2
O1
H13
-98(4)
Cl1
Cd1
N1
C1
79.7(2)
Cl1
Cd2
O1
H11
-73(2)
Cl1
Cd1
N1
C4
-95.2(2)
Cl1
Cd2
O1
H12
168(5)
Cl2
Cd1
N1
C1
-14.0(2)
Cl1
Cd2
O1
H13
62(4)
Cl2
Cd1
N1
C4
171.1(2)
N4
Cd2
O1
H11
32(2)
Cl2
Cd1
N1
C1
166.0(2)
N4
Cd2
O1
H12
-88(5)
Cl2
Cd1
N1
C4
-8.9(2)
N4
Cd2
O1
H13
167(4)
Cont…
[105]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
Cl2
Cd2
N2
C2
-95.5(2)
Cd1
N1
C4
H4
4.1(3)
Cl2
Cd2
N2
C3
79.5(2)
C1
N1
C4
C3
-0.8(3)
O1
Cd2
N2
C2
82.2(2)
C1
N1
C4
H4
179.2(2)
O1
Cd2
N2
C3
-102.8(2)
Cd2
N2
C2
C1
174.3(2)
N3
Cd2
N2
C2
176.1(2)
Cd2
N2
C2
H2
-5.7(3)
N3
Cd2
N2
C3
-8.8(2)
C3
N2
C2
C1
-0.7(3)
Cl1
Cd2
N2
C2
-8.1(2)
C3
N2
C2
H2
179.3(2)
Cl1
Cd2
N2
C3
166.9(2)
Cd2
N2
C3
C4
-173.0(2)
N4
Cd2
N2
C2
156.7(2)
Cd2
N2
C3
C5
8.6(2)
N4
Cd2
N2
C3
-28.3(4)
C2
N2
C3
C4
2.5(3)
Cl2
Cd2
N3
N4
89.3(2)
C2
N2
C3
C5
-175.9(2)
Cl2
Cd2
N3
C5
-84.6(1)
Cd2
N3
N4
N5
-174.7(2)
O1
Cd2
N3
N4
-95.2(2)
Cd2
N3
N4
Cd2
4.1(3)
O1
Cd2
N3
C5
90.9(2)
C5
N3
N4
N5
-0.4(2)
N2
Cd2
N3
N4
-178.2(2)
C5
N3
N4
Cd2
178.4(1)
N2
Cd2
N3
C5
7.9(1)
Cd2
N3
C5
N6
176.1(1)
Cl1
Cd2
N3
N4
169.2(2)
Cd2
N3
C5
C3
-6.9(3)
Cl1
Cd2
N3
C5
-4.7(3)
N4
N3
C5
N6
0.1(2)
N4
Cd2
N3
N4
-3.4(2)
N4
N3
C5
C3
177.1(2)
N4
Cd2
N3
C5
-177.3(2)
N3
N4
N5
N6
0.5(3)
Cl2
Cd2
Cl1
Cd1
4.52(2)
Cd2
N4
N5
N6
-178.3(1)
O1
Cd2
Cl1
Cd1
-171.49(5)
N4
N5
N6
C5
-0.4(2)
N2
Cd2
Cl1
Cd1
-87.52(5)
N5
N6
C5
N3
0.2(3)
N3
Cd2
Cl1
Cd1
-75.7(1)
N5
N6
C5
C3
-176.6(2)
N4
Cd2
Cl1
Cd1
96.69(5)
N1
C1
C2
N2
-1.9(3)
Cd1
Cl1
Cd2
Cl2
4.52(2)
N1
C1
C2
H2
178.1(2)
Cd2
Cl2
Cd1
Cl1
4.43(2)
H1
C1
C2
N2
178.1(2)
Cd1
N1
C1
H1
-2.3(3)
H1
C1
C2
H2
-1.9(4)
Cd1
N1
C1
C2
177.6(2)
N2
C3
C4
N1
-1.8(3)
C4
N1
C1
H1
-177.4(2)
N2
C3
C4
H4
178.2(2)
C4
N1
C1
C2
2.6(3)
C5
C3
C4
N1
176.5(2)
Cd1
N1
C4
C3
-175.9(2)
C5
C3
C4
H4
-3.5(4)
Cont…
[106]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
N2
C3
C5
N3
-1.2(3)
Cl2
Cd2
N3
C5
84.6(1)
N2
C3
C5
N6
175.3(2)
O1
Cd2
N3
N4
95.2(2)
C4
C3
C5
N3
-179.6(2)
O1
Cd2
N3
C5
-90.9(2)
C4
C3
C5
N6
-3.1(4)
N2
Cd2
N3
N4
178.2(2)
O1
Cd2
Cl2
Cd1
-56.2(6)
N2
Cd2
N3
C5
-7.9(1)
N2
Cd2
Cl2
Cd1
-85.95(5)
Cl1
Cd2
N3
N4
-169.2(2)
N3
Cd2
Cl2
Cd1
-155.99(5)
Cl1
Cd2
N3
C5
4.7(3)
Cl1
Cd2
Cl2
Cd1
4.56(2)
N4
Cd2
N3
N4
3.4(2)
N4
Cd2
Cl2
Cd1
108.99(5)
N4
Cd2
N3
C5
177.3(2)
Cl2
Cd2
O1
H11
133(2)
Cl2
Cd2
Cl1
Cd1
-4.52(2)
Cl2
Cd2
O1
H12
-107(5)
O1
Cd2
Cl1
Cd1
171.49(5)
Cl2
Cd2
O1
H13
-2(4)
N2
Cd2
Cl1
Cd1
87.52(5)
N2
Cd2
O1
H11
163(2)
N3
Cd2
Cl1
Cd1
75.7(1)
N2
Cd2
O1
H12
-77(5)
N4
Cd2
Cl1
Cd1
-96.69(5)
N2
Cd2
O1
H13
28(4)
Cd1
Cl1
Cd2
Cl2
-4.52(2)
N3
Cd2
O1
H11
-127(2)
Cd2
Cl2
Cd1
Cl1
-4.43(2)
N3
Cd2
O1
H12
-8(5)
Cd1
N1
C1
H1
2.3(3)
N3
Cd2
O1
H13
98(4)
Cd1
N1
C1
C2
-177.6(2)
Cl1
Cd2
O1
H11
73(2)
C4
N1
C1
H1
177.4(2)
Cl1
Cd2
O1
H12
-168(5)
C4
N1
C1
C2
-2.6(3)
Cl1
Cd2
O1
H13
-62(4)
Cd1
N1
C4
C3
175.9(2)
N4
Cd2
O1
H11
-32(2)
Cd1
N1
C4
H4
-4.1(3)
N4
Cd2
O1
H12
88(5)
C1
N1
C4
C3
0.8(3)
N4
Cd2
O1
H13
-167(4)
C1
N1
C4
H4
-179.2(2)
Cl2
Cd2
N2
C2
95.5(2)
Cd2
N2
C2
C1
-174.3(2)
Cl2
Cd2
N2
C3
-79.5(2)
Cd2
N2
C2
H2
5.7(3)
O1
Cd2
N2
C2
-82.2(2)
C3
N2
C2
C1
0.7(3)
O1
Cd2
N2
C3
102.8(2)
C3
N2
C2
H2
-179.3(2)
N3
Cd2
N2
C2
-176.1(2)
Cd2
N2
C3
C4
173.0(2)
N3
Cd2
N2
C3
8.8(2)
Cd2
N2
C3
C5
-8.6(2)
Cl1
Cd2
N2
C2
8.1(2)
C2
N2
C3
C4
-2.5(3)
Cl1
Cd2
N2
C3
-166.9(2)
C2
N2
C3
C5
175.9(2)
N4
Cd2
N2
C2
-156.7(2)
Cd2
N3
N4
N5
174.7(2)
N4
Cd2
N2
C3
28.3(4)
Cd2
N3
N4
Cd2
-4.1(3)
Cl2
Cd2
N3
N4
-89.3(2)
C5
N3
N4
N5
0.4(2)
Cont…
[107]
Chapter-2
Atom1
Atom2
Atom3
Atom4
Torsion
Atom1
Atom2
Atom3
Atom4
Torsion
C5
N3
N4
Cd2
-178.4(1)
H1
C1
C2
H2
1.9(4)
Cd2
N3
C5
N6
-176.1(1)
N2
C3
C4
N1
1.8(3)
Cd2
N3
C5
C3
6.9(3)
N2
C3
C4
H4
-178.2(2)
N4
N3
C5
N6
-0.1(2)
C5
C3
C4
N1
-176.5(2)
N4
N3
C5
C3
-177.1(2)
C5
C3
C4
H4
3.5(4)
N3
N4
N5
N6
-0.5(3)
N2
C3
C5
N3
1.2(3)
Cd2
N4
N5
N6
178.3(1)
N2
C3
C5
N6
-175.3(2)
N4
N5
N6
C5
0.4(2)
C4
C3
C5
N3
179.6(2)
N5
N6
C5
N3
-0.2(3)
C4
C3
C5
N6
3.1(4)
N5
N6
C5
C3
176.6(2)
Cl2
Cd1
Cl1
Cd2
4.58(2)
N1
C1
C2
N2
1.9(3)
Cl2
Cd1
Cl1
Cd2
-4.58(2)
N1
C1
C2
H2
-178.1(2)
Cl1
Cd2
Cl2
Cd1
-4.56(2)
H1
C1
C2
N2
-178.1(2)
Cl1
Cd2
Cl2
Cd1
4.56(2)
Atom1 Cd1 Cd1 Cd1 Cd1 Cd1 Cd1 Cd2 Cd2 Cd2 Cd2 Cd2 Cd2 Cl1 Cl2 O1 O1
Atom2 Cl1 N1 Cl1 N1 Cl2 Cl2 Cl2 O1 N2 N3 Cl1 N4 Cd2 Cd1 H11 H12
Type Unknown Unknown Unknown Unknown Polymeric Polymeric Unknown Unknown Unknown Unknown Polymeric Polymeric Polymeric Polymeric Unknown Unknown
Length 2.6276(6) 2.411(2) 2.6276(6) 2.411(2) 2.6036(6) 2.6036(6) 2.6344(7) 2.328(2) 2.417(2) 2.357(2) 2.5500(7) 2.284(2) 2.5500(7) 2.6036(6) 0.81(1) 0.82(5)
Atom1 O1 N1 N1 N2 N2 N3 N3 N4 N4 N5 N6 C1 C1 C2 C3 C3
Atom2 H13 C1 C4 C2 C3 N4 C5 N5 Cd2 N6 C5 H1 C2 H2 C4 C5
Type Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Polymeric Unknown Unknown Unknown Unknown Unknown Unknown Unknown
Length 0.82(3) 1.340(3) 1.339(3) 1.335(3) 1.342(3) 1.342(3) 1.330(2) 1.320(3) 2.284(2) 1.335(2) 1.335(3) 0.950(2) 1.390(2) 0.950(2) 1.391(2) 1.463(3)
Cont…
[108]
Chapter-2
Atom1
Atom2
Type
Length
Atom1
Atom2
Type
Length
C4
H4
Unknown
0.950(2)
N3
N4
Unknown
1.342(3)
Cd2
Cl2
Unknown
2.6344(7)
N3
C5
Unknown
1.330(2)
Cd2
O1
Unknown
2.328(2)
N4
N5
Unknown
1.320(3)
Cd2
N2
Unknown
2.417(2)
N4
Cd2
Polymeric
2.284(2)
Cd2
N3
Unknown
2.357(2)
N5
N6
Unknown
1.335(2)
Cd2
Cl1
Polymeric
2.5500(7)
N6
C5
Unknown
1.335(3)
Cd2
N4
Polymeric
2.284(2)
C1
H1
Unknown
0.950(2)
Cl1
Cd2
Polymeric
2.5500(7)
C1
C2
Unknown
1.390(2)
Cl2
Cd1
Polymeric
2.6036(6)
C2
H2
Unknown
0.950(2)
O1
H11
Unknown
0.81(1)
C3
C4
Unknown
1.391(2)
O1
H12
Unknown
0.82(5)
C3
C5
Unknown
1.463(3)
O1
H13
Unknown
0.82(3)
C4
H4
Unknown
0.950(2)
N1
C1
Unknown
1.340(3)
Cd1
Cl1
Polymeric
2.6276(6)
N1
C4
Unknown
1.339(3)
Cd1
Cl1
Polymeric
2.6276(6)
N2
C2
Unknown
1.335(3)
Cd2
Cl2
Polymeric
2.6344(7)
N2
C3
Unknown
1.342(3)
Cd2
Cl2
Polymeric
2.6344(7)
References [1] (a) Dinca, M., Dailly, A., Liu, Y., Brown, C.M., Neumann, D.A., Long, J.R., J. Am. Chem. Soc. 128 (2006) 16876 (b) Dinca, M., Yu, A.F., Long, J.R., J. Am. Chem. Soc. 128 (2006) 8904 (c) Dinca, M., Han, W. S., Liu, Y., Dailly, A., Brown, C.M., Long, J.R., Angew.Chem., Int. Ed. Engl. 46 (2007) 1419 (d) Zhao, H., Qu, Z. R., Ye, H.Y., Xiong, R. G., Chem. Soc. Rev. 38 (2008) 84 (e) Xiong, R.G., Xue, X., Zhao, H., You, X. Z., Abrahams, B.F., Xue, Z.-L., Angew. Chem., Int. Ed. 41 (2002) 3800 (f) Ye, Q., Song,Y.M., Wang, G.X., Chen,K., Fu,D.W., Chan, P.W.H., Xiong, R. G., J. Am. Chem. Soc. 128 (2006) 6554 (g) Ye, Q., Song, Y.M., Fu, D. W., Wang, G. X., Xiong, R. G., Chan, P.W.H., Huang, S.D., Cryst. Growth Des. 7 (2007) 1568 [109]
Chapter-2
(h) Wang, X.S., Tang, Y.Z., Huang, X.F., Qu, Z.R., Che, C.M., Chan, P.W.H., Xiong, R.G., Inorg. Chem. 44 (2005) 5278 (i) Wang, L.Z., Qu, Z.R., Zhao, H., Wang, X.S., Xiong, R.G., Xue, Z.L., Inorg. Chem. 42 (2003) 3969 (j) Tao, J., Ma, Z.J., Huang, R.B., Zheng, L.S., Inorg. Chem. 43 (2004) 6133 (k) Wu, T., Zhou, R., Li, D., Inorg. Chem. Commun. 9 (2006) 341 (l) Gaponik, P.N., Voitekhovich, S.V., Lyakhov, A.S., Matulis, V.E., Ivashkevich, O.A., Quesada, M., Reedijk, J., Inorg. Chim. Acta 358 (2005) 2549 (m) Shvedenkov, Y., Bushuev, M., Romanenko, G., Lavrenova, L., Ikorskii, V., Gaponik, P., Larionov, S., Eur. J. Inorg. Chem. (2005) 1678 (n) Wang, X.W., Chen, J.Z., Liu, J.H., Cryst. Growth Des. (2007) 1227 (o) Buchen, T., Schollmeyer, D., Gutlich, P., Inorg. Chem. 35 (1996) 155 (p) Jeftić, J., Hinek, R., Capelli, S.C., Hauser, A., Inorg. Chem. 36 (1997) 3080 [2] (a) Michelin, R.A., Mozzon, M., Bertani, R., Coor. Chem. Rev. 147 (1996) 299 (b) Guilard, R., Perrot, I., Tabard, A., Richard, P., Lecomte, C., Liu, Y.H., Kadish, K.M., Inorg. Chem. Soc. 30 (1991) 27 [3] (a) Himo, F., Demko, Z. P., Noodleman, L. and Sharpless, K. B., J. Am. Chem. Soc., 124 (2002) 12210 (b) Demko, Z.P. and Sharpless, K.B., J. Org. Chem. 66 (2001) 7945 [4]
Blake, J., Champness, N. R., Chung, S. S. M., Li, W.S. and Schroder, M., Chem. Commun. (1997) 1675
[5]
Zhang, X.M., Coord. Chem. Rev. 249 (2005) 1201
[6]
Lin, P., Clegg, W., Harrington, R. W. and Henderson, R. A., Dalton Trans. [110]
Chapter-2
(2005) 2388 [7]
Ye, Q., Li, Y.H., Song, Y.M., Huang, X.F., Xiong, R.G. and Xue, Z.L., Inorg. Chem. 44 (2005) 3619
[8]
Wang, X.S., Tang, Y.Z., Huang, X.F., Qu, Z.R., Che, C.M., Chan, P. W. H. and Xiong R.G., Inorg. Chem. 44 (2005) 5278
[9]
Wang, L.Z., Wang, X.S., Li, Y.H., Bai, Z.P., Xiong, R.G., Xiong, M. and Li, G.W., Chin. J. Inorg. Chem. 18 (2002) 1191
[10]
Li, Z., Li, M., Zhou, X.-P., Wu, T., Li, D., and Ng, S. W., Crystal Growth & Design 7-10 (2007) 1992
[11]
Qiu, Y., Liu, B., Peng, G., Cai, J., Deng, H., Zeller, M., Inorg. Chem. Commun. 13 (2010) 749
[12]
Youssef, M.A.M. Abu, Mautner, F.A., Massoud, A.A., Öhrström, L., Polyhedron. 26 (2007) 1531
[13]
Himo, F., Demko, Z. P., Noodleman, L. and Sharpless, K. B., J. Am.Chem. Soc. 125 (2003) 9983
[14]
Huang, X.F., Song, Y.M., Wu, Q., Ye, Q., Chen, X.B., Xiong, R.G., You, X. Z., Inorg. Chem. Commun. 8 (2005) 58
[15]
Yang, G.W., Li, Q.Y., Zhou, Y., Sha, P., Ma, Y.S., Yuan, R.X., Inorg. Chem. Commun. 11 (2008) 723
[16]
Tao, Y., Li, J. R., Yu, Q., Song, W.C., Bu, X. H., Cryst. Eng. Comm.10 (2008) 699
[17] (a) Singh, S., Mayer, P., Pandey, A., Indian J. Chem. 49A (2010) 1345 (b) Gupta, D.K., Singh, S., Mayer, P. , Pandey, A., Inorg. Chem. Commun. 14 (2011) 1485 [111]
CHAPTER 3 Some modified alkoxides based on Al, Ca, Mg and their sol-gel derived metal /mixed metal oxides
[112]
Chapter-3
Metal alkoxides are generally very reactive species due to the presence of electronegative alkoxy groups making the metal centers highly prone to nucleophilic attack. As a consequence of this, most of them are extremely sensitive to hydrolysis even by trace of moisture and require careful handling. The majority of the metal alkoxides are readily soluble in non-polar solvents making them suitable candidates for further reactions. Their reactions with a large number of organic hydroxyl compounds such as alcohols [1], glycols [2], carboxylic acids [3], hydroxyl acids, β-diketones [4], silanols, schiff bases [5] etc. result in the
stepwise removal of the alkoxy groups by the ligands giving
intermediate products which are stable enough to be isolated. This leads to the formation of modified alkoxides which are less prone to hydrolytic attack than their parent alkoxides. Chemical reactivities of metal alkoxides strongly depend on their molecular structures. For example, oligomeric metal alkoxides in which metal has a higher coordination number are less reactive, allowing better control on hydrolysis and condensation reactions. It appears that the resultant steric hindrance by anisotropic growth of oligomers inhibits the rapid hydrolysis that causes the formation of the polymeric gels in the sol-gel process. Therefore, reagents such as β-diketonates, carboxylic acids, glycols, etc. can modify the structures and reaction kinetics of metal alkoxides by chelation effect. Chemically modified metal/mixed metal alkoxides and related derivatives play an important role as precursors for synthesizing metal oxides / ceramic materials by sol-gel processing or metal organic chemical vapour deposition (MOCVD) techniques. These processes change the properties of metal oxides at nano-meter scale in the field of nanotechnology. Therefore, our emphasis is on the synthesis and characterization of tailor
[113]
Chapter-3
made precursors of these alkoxides prepared by the partial replacement of alkoxo groups with less hydrolysable groups such as oxo-, β-diketonates, and carboxylates modifiers, which lead to lower the rate of hydrolysis. Considerable research has been devoted to understand the structures of aluminum alkoxides. In general the aluminum atom has a tendency to increase it’s coordination number by chemical reactions, resulting in molecules containing tetrahedral and octahedral metal centers. For example, freshly distilled aluminum tris-isopropoxide exist as a trimer but after aging for a few weeks at 25 ⁰C it changes to a tetramer. [Al(OPri)3]4 which has been well characterized by 1H and
27
Al NMR indicating that the molecule
contains one central octahedral aluminum surrounded by three tetrahedral Al sites [6]. Whereas four- and six-coordinate Al is fairly common, very few five coordinate Al complexes have been structurally characterized [7]. Aluminum alkoxides are used as precursors for aluminum oxides and also have other important applications. For example, successive substitution of alkoxy groups with chelating ligands will reduce the Lewis acidity of the resulting complex [8]. Mehrotra and Gupta have reported [9] some acetylacetone and ethyl acetoacetate modified aluminum ethoxide and isopropoxide complexes. The structures of these monoand bis-β-diketonate alkoxide compounds were proposed to contain four- and fivecoordinated Al sites, respectively.
In the present work we have synthesized some carboxylic acid and β-diketone modified aluminum alkoxides which are analyzed by standard gravimetric aluminum analysis and isopropoxy analysis (for isopropoxides) by Bradley and Mehrotra method [10]. These
[114]
Chapter-3
compounds have also been characterized by IR, 1H and 13C NMR spectroscopies. In some cases
27
Al-NMR has also been used to establish the coordination environments around
the metal centers. Two of the synthesized compounds have also been characterized by single crystal X-ray crystallography.
Table 1: Physical properties of compounds (1-12) S. N.
Compound
i
Analyses Aluminum Isopropoxy (%) (%)
Physical state & Color
Yield of crude product
White Powder
97%
Calc= 11.3 Found=11.0
Calc=49.5 Found=48.9
1.
Al(OPr )2(OOCCH 2Cl)
2.
Al(OPri)(OOCCH2Cl)2
White Powder
97.3%
Calc=9.88 Found=9.83
Calc=21.64 Found=21.56
3.
Al(OPri)2(OOCCHCl2)
White Powder
98%
Calc=9.88 Found= 9.7
Calc=43.27 Found=42.8
Yellowish white Crystalline
97.8%
Al(OPri)(OOCCHCl2)2
Calc=7.89 Found=7.57
Calc= 17.28 Found=17.11
99%
Calc= 8.77 Found=8.69
Calc= 38.69 Found=38.27
95%
Calc=6.57 Found= 6.6
Calc= 14.48 Found=14.43
96%
Calc= 8.96 Found=8.88
Calc= 48.55 Found=47.54
Calc=7.58 Found=7.55
--
4.
5. Al(OPri)2(OOCCCl3)
White Powder
Al(OPri)(OOCCCl3)2
White Crystalline
Al(OBut)2(OOCCHCl2)
White Powder
6.
7.
8.
t
Al(OBu ) (OOCCHCl2)2
White Powder [115]
97.1%
Chapter-3
9.
10.
11.
12.
Al(OBut)2(OOCCCl3)
t
Al(OBu ) (OOCCCl3)2
Al(CH3COCHCOCH3)3
Al(CH3COC(Cl)COCH3)3
White Powder
97.8%
Calc=8.04 Found= 7.9
--
Yellow Powder
98.4%
Calc=6.35 Found=6.22
--
Crystalline White
95%
Calc= 8.24 Found=8.2
--
Crystalline Yellow
96.3%
Calc= 6.27 Found=6.2
--
Table 2: Important IR bands (in cm-1) S. N.
Compound
1
Al(OPri)2(OOCCH2Cl)
2
Al(OPri)(OOCCH2Cl)2
3
Al(OPri)2(OOCCHCl2)
4
Al(OPri)(OOCCHCl2)2
5
Al(OPri)2(OOCCCl3)
6
Al(OPri)(OOCCCl3)2
7
Al(OBut)2(OOCCHCl2)
8
Al(OBut) (OOCCHCl2)2 t
9
Al(OBu )2(OOCCCl3)
10
Al(OBut) (OOCCCl3)2
11 12
Al(CH3COCHCOCH3)3 Al(CH3COC(Cl)COCH3)3
νas CO2
νs CO2
1579 1580 1640 1589 1578 1669 1587 1582 1645 1580 1568 1677 1615 1538 1696 ---
1465 1460 1457 1468 1465 1459 1474 1462 1461 1462 1445 1439 1460 1434 1459 ---
[116]
δC-H gemMe2 1354
ν C-O terminal alkoxo 1176
ν C-O bridging alkoxo 1072
1345 1372 1340
-1118 --
1061 1018 1022
1350
1164
1017
1355
--
1032
--
940
1118 1099
---
-920
1108
----
----
1128 ---
Chapter-3
3.1 Synthesis and characterization of carboxylic acid modified aluminum alkoxides Aluminum isopropoxide Al(OPri)3 taken as parent alkoxide, was reacted with monochloroacetic acid (MCA) in 1:1 molar ratio, leading to the replacement of one of the isopropoxy group to give Al(OPri)2(O2C-CH2Cl) 1 (Scheme 1) as white solid, in high yield, which was purified by crystallization from toluene. Al(OPri)3 + ClCH2CO2H
Toluene
[Al(OPri)2 (O2CCH2Cl)]
N2 atm.
Scheme 1 The composition of compound 1 has been established by elemental and isopropoxy analyses. In the 1H NMR spectrum (Figure 1) the septets centered at δ 4. 676 and 4.373, correspond to two types of isopropoxy (CH of OPri) groups which is supported by mixed doublets at 1.678 (d, CH3 of OPri) while a peak at 2.108 corresponds to the proton of chloromethyl of monochloroacetic acid.
Figure 1: The 1H NMR spectrum of the compound 1 Unfortunately the spectrum is not significantly resolved. In the IR spectrum of compound 1, asymmetric and symmetric ν (COO-) vibrations were observed at 1579 and 1465 cm-1 [117]
Chapter-3
respectively with the Δν to be 114 cm-1. It may be deduced that COO- groups are bonded to the metal as bridging bidentate. The peak around 1354 cm-1 presents the vibration of CC gem-Me2 and peaks over 1176 and 1072 indicate C-O
terminal and bridging
isopropoxy groups respectively. In the 27Al NMR spectrum, a broad peak centered at 66.35 ppm indicates the presence of 4 and 5 coordination around Al atoms. The two singlets at 4.62 and 13.16 ppm show the presence of hexa- coordinated Al atoms (Figure 2).
Figure 2: The 27Al NMR spectrum of the compound 1 In the 13C NMR of compound 1, peak at δ 198.3 may be attributed for CO, peaks at 64.2 and 63.1 for CH3 of carboxylates, and those at 21.4 & 23.1 for alkoxo carbon. Unfortunately suitable single crystals of compound 1 could not be grown therefore, on
[118]
Chapter-3
the basis of analysis and characterization the proposed structure of the compound is as below (Figure 3). CH2Cl C O
i
Pr O
Al
O
OPr i OPr
i
Al
O
OPri
O C
CH2Cl Figure 3: The proposed structure of compound 1
When aluminum isopropoxide was reacted with monochloroacetic acid in 1:2 molar ratio under the same conditions, two isopropoxy groups were replaced by the chloroacetate groups giving the bis product Al(OPri)(O2CCH2Cl)2 2 (Scheme 2) which was purified by crystallization at -20 ⁰C.
Al(OPri)3 + 2ClCH2CO2H
Toluene
[Al(OPri)(O2CCH2Cl)2 ]
N2 atm. Scheme 2 On the basis of elemental and isopropoxy analyses the composition of compound 2 has been established as a bis substituted product of aluminum isopropoxide. In the 1H NMR spectrum, the peak at δ 3.64 indicate the -CH proton of isopropoxy group and doublet at δ 0.94 represents the protons of gem dimethyl groups. A singlet at δ 2.108 shows the presence of the proton of the chloromethyl group of acid (Figure 4).
[119]
Chapter-3
Figure 4: The 1H NMR spectrum of the compound 2 However, in absence of variable temperature NMR facility it has unfortunately not been possible for us to comment further. In the IR spectrum (Table 2) of compound 2 there are two sets of carboxylic groups for the asymmetric and symmetric COO - stretching. The vibrations observed at νas-1580 cm-1; νs-1460 cm-1 and νas-1640 cm-1; νs-1457 cm-1 correspond to bridging and terminal carboxylic groups respectively. The absorption at 1061 cm-1 indicates bridging isopropoxy groups. In the 27Al NMR spectrum, a broad peak centered at δ 61.34 suggested the presence of 4 and 5 coordinated Al atoms. In light of the above data, structure of compound 2 may be given as follows (Figure 5).
CH2Cl
C O
O
PriO
ClH2CCOO
Al
Al
OOCCH2Cl
OPri
O
O
C CH2Cl
Figure 5: Proposed molecular structure of the compound 2 [120]
Chapter-3
Table 3: 1H NMR data (in δ ppm) of Al(III) compounds
S. N.
Carboxylate/acetylacetonate acetate/proton
Compound
Isopropoxy/ tert. butoxy protons
CH2Cl/ CHCl2/CH3COCH i
1
Al(OPr )2(OOCCH2Cl)
3.695 s
2
Al(OPri)(OOCCH2Cl)2
3.261 s
3
Al(OPri)2(OOCCHCl2)
2.344 s
4
Al(OPri)(OOCCHCl2)2
2.283 s
5
Al(OPri)2(OOCCCl3)
--
6
Al(OPri)(OOCCCl3)2
--
7
Al(OBut)2(OOCCHCl2)
2.108 s
Al(OBut) (OOCCHCl2)2
2.107 s
Al(OBut)2(OOCCCl3)
--
Al(OBut) (OOCCCl3)2
--
Al(CH3COCHCOCH3)3
5.53s, 5.42s, 1.83s
Al(CH3COC(Cl)COCH3)3
5.31s, 1.69s
8 9 10 11 12
[121]
CH, 4.395 sept; gem-(CH3)2, 1.678 d CH, 3.642 sept; gem-(CH3)2, 0.917 d CH, 4.257 sept; gem-(CH3)2, 1.148 d CH, 4.036 sept; gem-(CH3)2, 1.253 d CH, 4.046 sept; gem-(CH3)2, 1.123 d CH, 3.942 sept; gem-(CH3)2, 0.977 d C(CH3)3, 1.47, 1.39 s CH3,1.143 s CH3, 1.155 s CH3, 1.129 s ---
Chapter-3
Table 4: Important 13C and 27Al NMR data (in δ ppm) of compounds Carboxylate/ acetylacetonate carbon CO CH3/CH
S. N.
Compound
1
Al(OPri)2(OOCCH2Cl)
64.244
198.3
Al(OPri)(OOCCH2Cl)2
--
--
Al(OPri)2(OOCCHCl2)
63.228
195.4
2 3
4
5
Al(OPri)(OOCCHCl2)2
--
--
Al(OPri)2(OOCCCl3)
77.451
187.98
Al(OPri)(OOCCCl3)2
--
--
7
Al(OBut)2(OOCCHCl2)
68.729
199.3
8
Al(OBut) (OOCCHCl2)2
66.651
201.45
9
Al(OBut)2(OOCCCl3)
75.911
200.7
10
Al(OBut) (OOCCCl3)2
78.569
195.3
Al(CH3COCHCOCH3)3
68.89
193.2
Al(CH3COC(Cl)COCH3)3
63.56
188.34
6
11 12
[122]
Isopropoxy /butoxy carbons
27
Al
CH3, 21.438 4.621, , 23.135, 13.169,6 CH , 78.024 6.350 --
61.343
CH3, 25.579 , 27.580, CH , 77.072
--
--
62.3
CH3, 27. 791 , 26.321, CH , 72.398
--
--
--
CH3, 33.539, C, 127.771
7.826, 59.481
C, 127.786
C, 128.137
59.206 6.116, 58.992 11.703, 58.199
--
--
--
--
C, 128.290
Chapter-3
Another modification of aluminum isopropoxide was done by reacting with dichloroacetic acid (DCA) in 1:1 molar ratio, leading to the replacement of one isopropoxy group to give Al(OPri)2(O2CCHCl2) 3 (Scheme 3).
Al(OPri)3 + HOOCCHCl2
Toluene Argon atm.
Al(OPri)2(OOCCHCl2)
Scheme 3 In the proton NMR spectrum (Figure 6), two septets centered at δ 4.279 & 4.257 indicate two types of CH protons of isopropoxy groups however, the spectrum as whole is not much resolved. A singlet at δ 2.344 shows the presence of the proton of the dichloromethyl group of the acid.
Figure 6: 1H NMR spectrum of the compound 3
In the IR spectrum of compound 3, asymmetric and symmetric COO- vibrations were observed at 1589 and 1468 cm-1 respectively with separation Δν of 121 cm-1. This indicated that COO- group is bonded to the metal as bridging bidentate. The absorptions [123]
Chapter-3
at 1118 and 1018 cm-1 have been attributed to terminal and bridging isopropoxy groups respectively. The composition of compound 3 was confirmed by elemental and isopropoxy analyses. In the
13
C NMR spectrum (Figure 7), peak at δ 195.4 ppm corresponds to the CO of
carboxylic group while peaks at 77.54 and 63.07 report CH2Cl. Peaks for isopropoxy carbons are visible at 27.74, 25.57 & 77.072 ppm.
Figure 7: 13C NMR spectrum of the compound 3
Thus according to the available data the proposed molecular structure would be as given in figure 8.
[124]
Chapter-3 CHCl2 C O
O
Pr iO
PriO
Al O Pri
OPri
Al
O
O C CHCl2
Figure 8: Proposed molecular structure of compound 3 It is noteworthy that although dichloroacetic acid is more acetic than monochloroacetic acid the composition of the product has not changed when compared with the similar product 1. Further when aluminum isopropoxide was treated with dichloroacetic acid in 1:2 molar ratio the two isopropoxy groups were replaced by the dichloroacetate groups (O2CCHCl2) of dichloroacetic acid. The product Al(OPri)(O2CCHCl2)2 4 was formed (Scheme 4). Al(OPri)3 +2HOOCCHCl2
Toluene Argon atm.
Al(OPri)(OOCCHCl2)2
Scheme 4 In 1H NMR spectrum, a septet centered at δ 4.036 due to -CH of isopropoxy group was observed. Two doublets at δ 1.181 and 1.253 correspond to gem -CH3 of isopropoxy. A singlet over 2.283 indicates the proton of dichloroacetic acid. In spectrum of 27Al NMR, a broad peak centered at δ 59.206 indicates the 4 and 5 coordination around Al (Figure 9).
[125]
Chapter-3
Figure 9:
27
Al NMR of compound 4
In IR spectrum of compound 4, vibrations observed at νas-1578 & νs-1465 cm-1 correspond to stretching of bidentate bridging COO- groups while the peaks at νas-1669 & νs-1459 cm-1 for terminal monodentate COO- groups. The absorption peak over 1022 cm-1 indicates the bridging alkoxy groups. The composition of compound 4 was also confirmed by elemental and isopropoxy analyses. From the above analyses we may propose a structure of the compound 4 as shown in figure 10.
Figure 10: The proposed molecular structure of compound 4
[126]
Chapter-3
In another reaction, aluminum isopropoxide Al(OPri)3 was reacted with trichloroacetic acid (TCA) in 1:1 molar ratio, leading to the replacement of one isopropoxy group to give Al(OPri)2(O2CCCl3) 5 (Scheme 5) as indicated by gravimetric estimation of Al. Toluene
Al(OPri)3 + HOOCCCl3
Argon atm.
Al(OPri)2(OOCCCl3)
Scheme 5 In the 1H NMR spectrum, a septet centered at δ 4.046 (CH of OPri) and doublet at 1.123 (d, CH3 of OPri) corresponds to isopropoxy groups. In the IR spectrum of compound 5, asymmetric and symmetric ν (COO -) vibrations were observed at 1587 and 1474 cm-1 respectively with frequency separation Δν of 113 cm-1. It is concluded that COO- group of the ligand was bonded to two metal centers in bridging bidentate mode. The absorptions at 1164 and 1017cm-1 are attributed to terminal and bridging isoproopoxy groups respectively. In 13C NMR spectrum, peak at 187.98 ppm corresponded to CO and the peak at 77.451 ppm for CH3 of the carboxylate group while the carbons of isopropoxy group were found at 33.539 and 127.771 ppm. In
27
Al NMR spectrum, peak at 65.7 ppm indicated 4-5 coordination around Al and
another peak at 6.5 ppm pointed hexa coordinated Al atoms. According to above analyses we may propose the following structure (Figure 11).
[127]
Chapter-3
CCl3 C O
O
Pr iO
PriO
Al
OPri
Al O Pri O
O C CCl3
Figure 11: Proposed structure of compound 5 Further, when aluminum isopropoxide was treated with trichloroacetic acid in 1:2 molar ratio the two isopropoxy groups were replaced by the trichloroacetate groups of trichloroacetic acid (O2CCCl3). The product Al(OPri)(O2CCCl3)2 6 was formed (Scheme 6). Al(OPri)3 + 2 HOOCCCl3
Toluene Argon atm.
Al(OPri)(OOCCCl3)2
Scheme 6 In IR spectrum of compound 6, vibrations observed at νas-1582 & νs-1462 cm-1 correspond to stretching of bidentate bridging COO- groups while the peaks at νas-1645 & νs-1461 cm-1 for terminal monodentate COO- groups. The absorption peak over 1032 cm1
indicates the bridging alkoxy groups.
In the 1H NMR spectrum, a septet centered at δ 3.942, corresponds to isopropoxy groups (CH of OPri) and doublet at 1.123 for gem CH3 of isopropoxy.
[128]
Chapter-3
On the basis of above analyses we may propose the structure of compound 6 as in figure 12. CCl3 C O
O
Cl3CCOO
Al
PriO OOCCCl3 O Pri
Al
O
O C CCl3
Figure 12: Proposed structure of compound 6 In the present work we have used the carboxylic acids such as monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) which have an increasing order of acidity. However, we find that this successive increase in acidity has no influence on the composition of the products in both 1:1 and 1:2 reactions. When we added three moles of the acid insoluble product were separated in short time. Since our interest was to make soluble precursors for sol-gel process so these insoluble products were not investigated further.
[129]
Chapter-3
In another reaction, we used aluminum tertiary butoxide [Al(OBut)3]2 as parent alkoxide, which was reacted with dichloroacetic acid in 1:1 molar ratio, leading to the replacement of one butoxy group to give Al(OBut)2(O2CCHCl2) 7 (Scheme 7) as indicated by gravimetric estimation of Al. Al(OBut)3 + HOOCCHCl2
Toluene Argon atm.
Al(OBut)2(OOCCHCl2)
Scheme 7 In the 1H NMR spectrum (Figure 13) of compound 7, two singlets at δ 1.467 and 1.29 indicate two types of tertiary butoxy protons. A singlet centered at δ 2.108 for the –CH of dichloromethyl group of acid was also observed.
Figure 13: 1H NMR spectrum of compound 7 In IR spectrum of compound 7, asymmetric and symmetric vibrations of COO- groups were observed at 1580 and 1462 cm-1 respectively. The frequency separation (Δν) of asymmetric and symmetric carboxylic groups in the compound is 118 cm-1 which
[130]
Chapter-3
indicates bridging bidentate mode of attachment. The absorptions at 940 and 1018cm-1 are attributed to terminal and bridging butoxy respectively. In the 13C NMR spectrum of compound 7, peak at 199.3 ppm corresponds to CO and the peak at 68.66 for CH3 of carboxylic groups, while the carbons of isopropoxy group were found at 33.539, 127.771 ppm. In 27Al NMR spectrum, a broad peak centered at δ 62.59 indicates 4 & 5 coordinated Al metals and sharp peak at 11.03 may be attributed to 6 coordinated Al metal centers (Figure 14).
Figure 14: A spectrum of 27Al NMR of compound 7 Based on the available data we may propose a structure for compound 7 as shown in figure 15.
[131]
Chapter-3
CHCl2 C
O
O
OBut ButO
Al
Al
OBut
O But
O
O C CHCl2
Figure 15: Proposed structure of compound 7 Aluminum tertiary butoxide {Al(OBut)3} was reacted with dichloroacetic acid in 1:2 molar ratio, leading to the replacement of
two butoxy groups to give Al(OBut)
(O2CCHCl2)2 8 (Scheme 8).
Al(OBut)3 + 2 HOOCCHCl2
Toluene Argon atm.
Al(OBut)(OOCCHCl2)2
Scheme 8 In the 1H NMR spectrum of compound 8, two singlets at δ 1.047 and 1.549 indicate two types of tertiary butoxy protons. A singlet at δ 2.107 for the proton of dichloromethyl group of acid. In IR spectrum of compound 8, vibrations observed at νas-1568 & νs-1445 cm-1 correspond to stretching of bidentate bridging COO- groups while the peaks at νas-1677 & νs-1439 cm-1 for terminal monodentate COO- groups. The absorption peak over 1092 cm-1 indicates the bridging alkoxy groups.
[132]
Chapter-3
In the
13
C NMR spectrum, peak at 201.45 ppm corresponded to CO and the peak at
66.651 ppm for CH3 of carboxylate group while the carbons of isopropoxy group were found at 31.7 and 127.786. In
27
Al NMR of compound 8, the broad peak centered at δ 59.20 indicates the 4 and 5
coordination around Al atoms (Figure 16).
Figure 16: 27Al NMR of compound 8 On the basis of above analysis proposed molecular structure should be similar to compound 4 (Figure 10). Another modification of aluminum tertiary butoxide was done with trichloroacetic acid in 1:1 molar ratio, to give Al(OBut)2(O2CCCl3) 9 by the replacement of one butoxy group (Scheme 9).
Al(OBut)3 + HOOCCCl3
Toluene Argon atm. Scheme 9
[133]
Al(OBut)2(OOCCCl3)
Chapter-3
In the 1H NMR spectrum of compound 9, two singlets at δ 1.387 and 1.475 indicate two types of tertiary butoxy groups (Figure 17).
Figure 17: 1H NMR spectrum of compound 9 In IR spectrum of the compound 9, asymmetric and symmetric of COO- vibrations observed at 1615 and 1460 cm-1 respectively have a frequency separation Δν of 255 cm-1. It is concluded that COO- group of ligand was bonded to the metal as bridging bidentate. The absorptions at 920 and 1088cm-1 are attributed to terminal and bridging butoxy groups respectively. In
27
Al NMR spectrum of compound 9, the broad peaks centered at δ 58.99 and 6.11
indicate the 4 and 6 coordination of Al atom (Figure 18).
[134]
Chapter-3
Figure 18: A spectrum of 27Al NMR of compound 9 In the 13C NMR peaks at δ 200.7 for acid CO, δ 75.91 for acid CCl3 and δ 31.7 & 127.786 corresponds to carbon of OCMe3 groups. The structure of compound 9, on the basis of above characterization and estimation, may be proposed as that of complex 7 (Figure 15). However, due to the absence of single crystal analysis the structure of the molecule could not be confirmed. Further modification of Al(OBut)3 was done by reacting with trichloroacetic acid in 1:2 molar ratio to give
Al(OBut)(O2CCCl3)2 10 (Scheme 10) which is confirmed by
gravimetric Al analysis. Al(OBut)3 + 2 HOOCCCl3
Toluene Argon atm. Scheme 10
Al(OBut)(OOCCCl3)2
In the 1H NMR spectrum of compound 10, two singlets at δ 1.325 and 1.467 indicate two types of tertiary butoxy groups. In
27
Al NMR spectrum of 10 the broad peak centered at δ 58.19 suggests penta
coordinated Al centers and an arm at 11.7 ppm represents octa-coordinated Al (Figure 19).
[135]
Chapter-3
Figure 19: 27Al NMR of compound 10 In IR spectrum of compound 10, vibrations observed at νas-1538 and νs-1434 cm-1 correspond to the stretching of bidentate bridging COO- groups while the peaks at νas1696 and νs-1459 cm-1 for stretching of terminal monodentate COO- groups. The absorption peak over 1078 cm-1 indicates the bridging alkoxy groups. In 13C NMR peaks at δ 195.3 for the CO and 78.56 for CCl3 of the acid. The peaks at δ 30.84 and 128.137 ppm correspond to butoxy carbons. In spite of our best efforts, suitable single crystals of the product could not be formed. However, based on the above analyses the structure of molecule may be propose to be similar to complex 4 (Figure 10).
When we have done the reaction of Al(OBut)3 in 1: 3 molar ratio with acids the solid product was formed, which is insoluble common solvents. Since our aim was to synthesize soluble compounds which may be used as precursors in the sol-gel process. Therefore further characterizations of the insoluble products were not pursued.
[136]
Chapter-3
3.2 Synthesis and characterization of β-diketone modified Aluminum alkoxides We have also investigated the gradual replacement of alkoxy groups with acetylacetone and it’s chloro derivative. When the reaction of aluminum isopropoxide was done with acetylacetone in 1:1 molar ratio in refluxing toluene for 8 h. It was found that all isopropoxy
groups
were
replaced
by
the
acetylacetonate.
The
product
Al(CH3COCHCOCH3)3 11 was formed. Compound 11 was crystallized in cubic crystal system at room temperature after 48 h which was examined by single crystal X-ray crystallography. Aluminum has octahedral coordination with oxygen atoms of the three acetylacetonate groups (Figure 20).
J. H. Wengrovius et al. studied the kinetics of
formation and disproporotionation of Al(OR)(acac)2 complexes in solution at higher temperatures and have concluded that such complexes are unstable and get disproporotionated (Scheme 11) to give Al(acac)3. [Al(OR)(β-diketonate)2]2
[Al(β-diketonate)3] + ½ [Al(OR)2(β-diketonate)] Scheme 11
The obtained product 11 as well as a similar product 12 upon 1:1 reaction between aluminum alkoxides and b- diketones futher substantiates their conclusion. Single crystal structure of compound 11 (prepared by different synthetic method) was published [11(b)] in the next month we got our data.
Figure 20: ORTEP of Al(CH3COCHCOCH3)3 [137]
Chapter-3
In another reaction, aluminum tertiary butoxide was reacted with 3-chloroacetylacetone in 1:1 molar ratio. It was found that all isopropoxy groups were replaced by the 3- chloro acetylacetonate groups and the tris-substituted product Al(CH3COCClCOCH3)3 12 was formed. When the crude product was kept in toluene in inert atmosphere at room temperature for 48 h, cubic shaped transparent white crystals were obtained (Scheme 12). In FT-IR spectrum of compound 12 several signals in IR region (400-4000 cm-1) indicate the presence of organic ligands. Signals observed at 461 and 464 cm-1 may be assigned to bending mode of Al-O vibration, while at 765, 831,905 and 943 cm-1 due to νAl-O vibrations. One of the crystals examined by single crystal X-ray crystallography (Figure 21) was proven to be Al(CH3COC(Cl)COCH3)3.
(a)
(b)
Figure 21: Ball stick model of Al(CH3COCClCOCH3)3 (a) and packing of crystals(b)
[138]
Chapter-3
Compound 12 was crystallized in cubic crystal system with P 4 -3n space group. Each Al atom is bonded with three molecules of 3-chloroacetylacetone. The bond lengths and bond angles of the organic ligand are in the expected range. The hexa coordinated central metal atom is linked to six oxygen atoms from three chelating bidentate 3-chloro acetyleacetonate ligands. The Al-O bond lengths vary between 1.871- 1.79 Å (Table 7) range and are in excellent agreement with the reported values [12, 13]. The cis- O-Al-O angles which range from 88.2 to 92.1⁰ and the trans O-Al-O angle of 178.5⁰ indicate a little distortion of the AlO6 octahedron. Each [Al(C2H6O2Cl)3] molecule is linked to three other symmetry related molecules via weak C-H…O and C-H…Cl interactions. All carbon atoms bearing hydrogen, act as H donors, while the O and Cl of each 3-chloro acetylactonate ligand function as H accepters. All three C-H…O interactions are separated by 2.659 Å and C-H…Cl interactions have the value of 2.894 Å (Figure 22).
Figure 22: Showing C-H…O and C-H…Cl interactions in Al(C2H6O2Cl)3
[139]
Chapter-3
In the 1H NMR spectrum, the only singlet observed at δ 1.69 belongs to CH3 of 3chloroacetylacetone. This indicates that the solid state structure is retained in solution.
Table 5: Crystallographic data for Compound 12 Empirical formula Mr/g mol−1 Compound Radiation Diffractometer Crystal System Space group a(Å) b(Å) c(Å) α(°) β(°) γ(°) V(Å3) Z
C15H18AlCl3O6 427.66 12 MoKα ‘Oxford XCalibur’ Cubic P - 4¯ 3 n 16.3909(19) 16.3909(19) 16.3909(19) 90 90 90 4403.61 8
Table 6: Bond angles of compound 12 Atom1 C2 O1 O1 C3 C2 C2 C2 H33 H33 H32 C2 C2 Cl5 C4 C4 C7
Atom2 O1 C2 C2 C2 C3 C3 C3 C3 C3 C3 C4 C4 C4 C6 C6 C6
Atom3 Al5 C3 C4 C4 H33 H32 H31 H32 H31 H31 Cl5 C6 C6 C7 O8 O8
Angle 129.3(2) 116.6(3) 121.9(3) 121.4(3) 108.0(4) 108.4(4) 110.1(4) 107.4(4) 111.9(4) 110.9(4) 117.3(3) 123.8(3) 118.6(3) 121.4(3) 122.2(3) 116.4(3)
Atom1 C2 C2 C2 H33 H33 H32 C2 C2 Cl5 C4 C4 C7 C6 C6 C6 H73 [140]
Atom2 C3 C3 C3 C3 C3 C3 C4 C4 C4 C6 C6 C6 C7 C7 C7 C7
Atom3 H33 H32 H31 H32 H31 H31 Cl5 C6 C6 C7 O8 O8 H73 H72 H71 H72
Angle 108.0(4) 108.4(4) 110.1(4) 107.4(4) 111.9(4) 110.9(4) 117.3(3) 123.8(3) 118.6(3) 121.4(3) 122.2(3) 116.4(3) 109.3(4) 110.5(4) 109.5(4) 109.0(5)
Chapter-3
C6 C6 C6 H73 H73 H72 C6 O1 O1 O1 O1 O1 O8 O8 O8 O8 O1 O1 O1 O8 O8 O1 Al5 O1 O1 C3
C7 C7 C7 C7 C7 C7 O8 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 O1 C2 C2 C2
H73 H72 H71 H72 H71 H71 Al5 O8 O1 O8 O1 O8 O1 O8 O1 O8 O8 O1 O8 O1 O8 O8 C2 C3 C4 C4
109.3(4) 110.5(4) 109.5(4) 109.0(5) 108.7(5) 109.7(5) 129.3(2) 90.3(1) 88.2(1) 178.5(1) 88.2(1) 92.1(1) 92.1(1) 89.3(1) 178.5(1) 89.3(1) 90.3(1) 88.2(1) 178.5(1) 92.1(1) 89.3(1) 90.3(1) 129.3(2) 116.6(3) 121.9(3) 121.4(3)
H73 H72 Al5 Al5 O1 O1 C3 C2 C2 C2 H33 H33 H32 C2 C2 Cl5 C4 C4 C7 C6 C6 C6 H73 H73 H72 Al5
C7 C7 O8 O1 C2 C2 C2 C3 C3 C3 C3 C3 C3 C4 C4 C4 C6 C6 C6 C7 C7 C7 C7 C7 C7 O8
H71 H71 C6 C2 C3 C4 C4 H33 H32 H31 H32 H31 H31 Cl5 C6 C6 C7 O8 O8 H73 H72 H71 H72 H71 H71 C6
Atom1 C3 C3 C3 C4 C4 C6 C6 C7 C7 C7 O1
Atom2 H33 H32 H31 Cl5 C6 C7 O8 H73 H72 H71 C2
Type Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
108.7(5) 109.7(5) 129.3(2) 129.3(2) 116.6(3) 121.9(3) 121.4(3) 108.0(4) 108.4(4) 110.1(4) 107.4(4) 111.9(4) 110.9(4) 117.3(3) 123.8(3) 118.6(3) 121.4(3) 122.2(3) 116.4(3) 109.3(4) 110.5(4) 109.5(4) 109.0(5) 108.7(5) 109.7(5) 129.3(2)
Table 7: Bond lengths of compound 12 Atom1 O1 O1 C2 C2 C3 C3 C3 C4 C4 C6 C6
Atom2 C2 Al5 C3 C4 H33 H32 H31 Cl5 C6 C7 O8
Type Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
Length 1.263(4) 1.879(3) 1.497(5) 1.408(6) 1.010(4) 0.999(5) 0.976(5) 1.752(4) 1.399(5) 1.501(6) 1.273(4) [141]
Length 1.010(4) 0.999(5) 0.976(5) 1.752(4) 1.399(5) 1.501(6) 1.273(4) 0.962(5) 0.970(5) 0.966(5) 1.263(4)
Chapter-3
C7 C7 C7 O8 Al5 Al5 Al5 Al5 O1 C2 C2
H73 H72 H71 Al5 O1 O8 O1 O8 C2 C3 C4
Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
0.962(5) 0.970(5) 0.966(5) 1.871(3) 1.879(3) 1.871(3) 1.879(3) 1.871(3) 1.263(4) 1.497(5) 1.408(6)
C2 C2 C3 C3 C3 C4 C4 C6 C6 C7 C7 C7
C3 C4 H33 H32 H31 Cl5 C6 C7 O8 H73 H72 H71
Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
1.497(5) 1.408(6) 1.010(4) 0.999(5) 0.976(5) 1.752(4) 1.399(5) 1.501(6) 1.273(4) 0.962(5) 0.970(5) 0.966(5)
Table 8: All torsion angles of compound 12 Atom1 Al5 Al5 C2 C2 C2 C2 C2 O1 O1 O1 C4 C4 C4 O1 O1 C3 C3 C2 C2 Cl5 Cl5 C4 C4 C4 O8 O8 O8 C4
Atom2 O1 O1 O1 O1 O1 O1 O1 C2 C2 C2 C2 C2 C2 C2 C2 C2 C2 C4 C4 C4 C4 C6 C6 C6 C6 C6 C6 C6
Atom3 C2 C2 Al5 Al5 Al5 Al5 Al5 C3 C3 C3 C3 C3 C3 C4 C4 C4 C4 C6 C6 C6 C6 C7 C7 C7 C7 C7 C7 O8
Atom4 C3 C4 O8 O1 O8 O1 O8 H33 H32 H31 H33 H32 H31 Cl5 C6 Cl5 C6 C7 O8 C7 O8 H73 H72 H71 H73 H72 H71 Al5
Torsion 170.5(3) -10.4(5) 17.9(3) -74.2(3) -60(5) 162.5(3) 107.3(3) 131.3(4) 112.7(4) -8.8(5) 49.6(5) -66.4(5) 172.1(4) 179.3(3) -5.9(6) -0.2(5) 173.2(4) 170.8(4) 7.4(6) 2.6(5) 179.2(3) 174.1(4) 54.2(6) -66.8(5) -4.2(6) 124.1(4) 114.8(4) 7.3(5)
Atom1 O1 O8 O1 Al5 Al5 O1 O1 O1 C4 C4 C4 O1 O1 C3 C3 C2 C2 Cl5 Cl5 C4 C4 C4 O8 O8 O8 C4 C7 Al5 [142]
Atom2 Al5 Al5 Al5 O1 O1 C2 C2 C2 C2 C2 C2 C2 C2 C2 C2 C4 C4 C4 C4 C6 C6 C6 C6 C6 C6 C6 C6 O1
Atom3 O8 O8 O8 C2 C2 C3 C3 C3 C3 C3 C3 C4 C4 C4 C4 C6 C6 C6 C6 C7 C7 C7 C7 C7 C7 O8 O8 C2
Atom4 C6 C6 C6 C3 C4 H33 H32 H31 H33 H32 H31 Cl5 C6 Cl5 C6 C7 O8 C7 O8 H73 H72 H71 H73 H72 H71 Al5 Al5 C3
Torsion -30(5) 108.4(3) -16.2(3) 170.5(3) -10.4(5) 131.3(4) 112.7(4) -8.8(5) 49.6(5) -66.4(5) 172.1(4) 179.3(3) -5.9(6) -0.2(5) 173.2(4) 170.8(4) 7.4(6) 2.6(5) 179.2(3) 174.1(4) 54.2(6) -66.8(5) -4.2(6) 124.1(4) 114.8(4) 7.3(5) 174.4(3) 170.5(3)
Chapter-3
C7 C6 C6 C6 C6 C6 O1 O8 O8 O1 O8 O1 O8 O1 O1 O8 O1 O8 O1 O8 O8 O1 O8
C6 O8 O8 O8 O8 O8 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5 Al5
O8 Al5 Al5 Al5 Al5 Al5 O1 O1 O1 O1 O1 O8 O8 O8 O8 O8 O1 O1 O1 O1 O1 O8 O8
Al5 O1 O1 O8 O1 O8 C2 C2 C2 C2 C2 C6 C6 C6 C6 C6 C2 C2 C2 C2 C2 C6 C6
174.4(3) -16.2(3) 72.0(3) 162.3(3) -30(5) 108.4(3) 162.5(3) 107.3(3) 17.9(3) -74.2(3) -60(5) -30(5) 108.4(3) -16.2(3) 72.0(3) 162.3(3) -74.2(3) -60(5) 162.5(3) 107.3(3) 17.9(3) 72.0(3) 162.3(3)
Al5 O1 O1 O1 C4 C4 C4 O1 O1 C3 C3 C2 C2 Cl5 Cl5 C4 C4 C4 O8 O8 O8 C4 C7
O1 C2 C2 C2 C2 C2 C2 C2 C2 C2 C2 C4 C4 C4 C4 C6 C6 C6 C6 C6 C6 C6 C6
C2 C3 C3 C3 C3 C3 C3 C4 C4 C4 C4 C6 C6 C6 C6 C7 C7 C7 C7 C7 C7 O8 O8
C4 H33 H32 H31 H33 H32 H31 Cl5 C6 Cl5 C6 C7 O8 C7 O8 H73 H72 H71 H73 H72 H71 Al5 Al5
-10.4(5) 131.3(4) 112.7(4) -8.8(5) 49.6(5) -66.4(5) 172.1(4) 179.3(3) -5.9(6) -0.2(5) 173.2(4) 170.8(4) 7.4(6) 2.6(5) 179.2(3) 174.1(4) 54.2(6) -66.8(5) -4.2(6) 124.1(4) 114.8(4) 7.3(5) 174.4(3)
3.3 Heterometallic alkoxides We have also prepared some mixed metal alkoxides of aluminum, by the reaction of aluminum alkoxides with Ca and Mg acetates (compound 13-16). The use of heterometallic alkoxides as precursors for mixed metal oxides has been increased significantly in the last two decades [14-16]. Metal salts such as nitrate, halides [17], acetates [18,19], β-diketones [20] and hydroxides are the most common compounds associated with metal alkoxides. The structural characterization of complexes is important for understanding the relationship between the precursor and the final oxide material in the sol-gel process. In general, metal acetates are the most common precursors associated with metal alkoxides. Structural features of the products obtained by treating metal acetates with metal alkoxides show that the acetate ligand is bridging bidentate or
[143]
Chapter-3
bridge-chelating, indicating the role of the carboxylate group in maintaining the stoichiometry during the various stages of the transformation that leads to mixed metal oxides. Reactions between metal alkoxides and metal acetates have generally been reported to give oxo products by the elimination of an ester. A. Pandey et al. [21] have reported heterometallic alkoxide [Pb2 Al5(µ3-O)(µ4-O)(OAc)3(OPri)3(µ-OPri)9] by the reaction of lead acetate and aluminum isopropoxide in 1:2 molar ratio. The compound represents a unique example in which aluminum is present in three different coordination environments. The penta coordination around the two lead atoms has distorted tetragonal geometry (Figure 23). In present work, instead of lead we have used magnesium and calcium acetates with the aluminum alkoxides.
Figure 23: Plot of the molecular core of Pb2 Al5(µ3-O)(µ4-O)(µ-OPri)9(OPri)3(µ-OAc)
[144]
Chapter-3
Table 9: Physical properties of compounds (13-16) S. N.
Compound
13.
Mg2Al5(O)2(OAc)3(OPri)12
14.
15.
16.
Physical state & Color Yellow viscous liquid
Analyses Aluminum Isopropoxy (%) (%)
Yield of crude product 97%
Calc= 12.24 Calc=64.35 Found=12.00 Found=64.02
White viscous liquid
97.9%
Calc=11.9 Calc=62.55 Found=10.98 Found=61.78
t
Yellow viscous liquid
97.94%
Calc=10.62 Found=10.5
--
t
White viscous liquid
98.9%
Calc=10.36 Found=10.13
--
Ca2Al5(O)2(OAc)3(OPri)12
Mg2Al5(O)2(OAc)3(OBu )12
Ca2Al5(O)2(OAc)3(OBu )12
Table 10: Important IR bands (in cm-1) S. N.
Compound
13
Mg2Al5(O)2(OAc)3(OPri)12
νas CO2
1696
νs CO2
Δ C-H gemMe2
ν C-O terminal alkoxo
ν C-O bridging alkoxo
1459
1357
1112
1078
Ca2Al5(O)2(OAc)3(OPri)12
1538
1434
1349
1131
1012
Mg2Al5(O)2(OAc)3(OBut)12
1578
1466
--
951
1091
Ca2Al5(O)2(OAc)3(OBut)12
1648
1548
--
910
1101
14.
15.
16.
[145]
Chapter-3
Table 11: 1H NMR spectra (in ppm) of Al, Ca and Mg compounds S. N.
Compound
3.499 s
Isopropoxo/ tert. butoxy protons CH, 4.221 sept; gem-(CH3)2, 1.213, 1.203 d CH, 4.417 sept; gem-(CH3)2, 1.677, 1.404 d
1.421 s
CH3,1.155 s
1.419 s, 1.462 s
CH3, 1.102 s
Carboxylate proton
Mg2Al5(O)2(OAc)3(OPri)12
13
3.505 s Ca2Al5(O)2(OAc)3(OPri)12
14 15 16
Mg2Al5(O)2(OAc)3(OBut)12 Ca2Al5(O)2(OAc)3(OBut)12
Table 12: Important 13C and 27Al NMR data (in ppm) of compounds S. N.
Compound
Acetate carbons CH3
13
14 15 16
Mg2Al5(O)2(OAc)3(OPri)12 Ca2Al5(O)2(OAc)3(OPri)12 Mg2Al5(O)2(OAc)3(OBut)12 Ca2Al5(O)2(OAc)3(OBut)12
Isopropoxy/butoxy carbons
27
Al
CO
80.21
201.09
79.14
193.00
75.91
199.8
76.87
186.8
CH3, 26.572, 27.840; C, 66.330 CH3, 26.557, 27.840; C , 63.488 CH3, 31.278, 33.830; C, 127.71 CH3, 31.278, 33.692; C, 127.771
4.590, 63.022 4.590, 65.678 54.26 52.398
Firstly we have used use aluminum isopropoxide for the preparation of heterometallic alkoxide, where it was reacted with magnesium acetate [Mg(OAc)2] in 2:1 molar ratio (Scheme 13) to give product Mg2Al5(O)2(OAc)3(OPri)12 13. The composition of product 13 has been proposed on the basis of Al gravimetric analysis and isopropoxy analysis. Toluene 2 Al(OPri)3 + Mg(OOCCH3)2 8 hours reflux (Argon atm.)
Scheme 13 [146]
Mg2Al5 (O)2 (OOCCH3)3(OPri)12
Chapter-3
In 1H NMR spectrum of compound 13, the septet centered at δ 4.39 indicates the -CH proton of isopropoxy group and three doublets at δ 1.33, 1.404 and 1.677 represent the protons of gem dimethyl groups. A singlet at δ 2.108 shows the presence of acetate proton (Figure 24).
Figure 24: 1H NMR spectrum of compound 13 In 27Al NMR spectrum, a broad peak centered at δ 63.02 suggests the penta coordinated Al atoms and sharp peak at δ 4.59 for an octa-coordinated Al (Figure 25).
Figure 25: 27Al NMR spectrum of compound 13
[147]
Chapter-3
In 13C NMR spectrum, peak at δ 201.09 is the indication for carbonyl carbon and δ 80.21 for methyl of acetate groups. Peaks at δ 26.572 and 27.840 correspond to CH and at δ 66.33 to CH3 of isopropoxide groups. In IR spectrum of compound 13, vibrations observed at νas-1568 and νs-1455 cm-1 correspond to the stretching of bidentate bridging COO- groups while absorption peaks at 1012 and 1123 cm-1 indicate the bridging and terminal alkoxy groups. When aluminum isopropoxide was reacted with calcium acetate in 2:1 molar ratio (Scheme 14) the product 14 having similar composition as 13 (on the basis of Al gravimetric analysis and isopropoxy analysis) was obtained. Toluene 2Al(OPri)3 + Ca(OOCCH3) 2 8 hours reflux (Argon atm.)
Ca2Al5 (O)2 (OOCCH3)3(OPri)12
Scheme 14 In 1H NMR spectrum of compound 14, the septet peak at δ 4.413 indicates the -CH proton of isopropoxy group and three doublets at δ 1.38, 1.423 and 1.67 represent the protons of gem dimethyl groups. A singlet at δ 2.109 shows the presence of acetate proton. In 27Al NMR spectrum of compound 14, the broad peak centered at 65.67 ppm suggests the penta coordinated Al atoms and the sharp peak at 4.5 ppm for octa coordinated Al (Figure 26).
[148]
Chapter-3
Figure 26: 27Al NMR spectrum of compound 14 In 13C NMR spectrum, peak at δ 193.00 assigned to the carbonyl carbon of acetate and at 79.14 to the carbon of CH3 of acetate group. Peaks at 26.557 & 27.84 correspond to the carbon of CH and at 63.48 to the carbon of CH3 of isopropoxy groups. In IR spectrum of compound 14, vibrations observed at νas-1578 and νs-1466 cm-1 correspond to the stretching of bidentate bridging COO- groups. The absorptions at 1021 and 1151 cm-1 indicate the bridging and terminal alkoxy groups. Due to the absence of single crystal analysis, structure of compound 14 could not be specified. Further aluminum tertiary butoxide was reacted with magnesium acetate in 2:1 molar ratio (Scheme 15) to yield product 15. The composition of product 15 has been proposed on the basis of Al gravimetric analysis
Toluene 2 Al(OBut)3 + Mg(OOCCH3)2 8 hours reflux (Argon atm.)
Scheme 15
[149]
Mg2Al5 (O)2 (OOCCH3)3(OBut)12
Chapter-3
In 1H NMR spectrum (Figure 27) of compound 15, two singlets at δ 1.421 and 1.515 indicate the protons of bridging and terminal tertiary butoxy groups and a singlet at δ 2.109 represents the presence of acetate proton.
Figure 27: 1H NMR of compound 15
In IR spectrum of compound 15, vibrations observed at νas-1575 & νs-1460 cm-1 correspond to the stretching of bidentate bridging COO- groups. The absorption peaks at 1021 and 1132 cm-1 indicate the bridging and terminal alkoxy groups. In 27Al NMR spectrum, the broad peak centered at 54.260 ppm suggests the tetrahedral and pentagonal coordination around Al atoms (Figure 28).
[150]
Chapter-3
Figure 28:
27
Al NMR of compound 15
In 13C NMR spectrum (Figure 29), peak at δ 199.8 is the indicative of carbon of CO, at δ 75.91 of CH3 of acetate group and at δ 31.278, 33.830 and 127.71 of carbons of tertiary butoxides.
Figure 29:
13
C NMR of compound 15
[151]
Chapter-3
Further modification of aluminum tertiary butoxide was done by the reaction with calcium acetate in 2:1 molar ratio (Scheme 16) to yield product 16. The composition of product 16 has been proposed on the basis of Al gravimetric analysis Toluene 2Al(OBut)3 + Ca(OOCCH3) 2 Ca2Al5 (O)2 (OOCCH3)3(OBut)12 8 hours reflux (Argon atm.)
Scheme 16 In 1H NMR spectrum (Figure 27) of compound 16, two singlets at δ 1.419 and 1.514 indicate the two types of tertiary butoxy groups (bridging and terminal) and a singlet at δ 2.09 represents -CH3 of acetate group. In
27
Al NMR spectrum of compound 16, a broad peak at 52.398 ppm suggests the
tetrahedral and pentagonal coordination around Al atoms (Figure 30).
Figure 30: 27Al NMR of compound 16 In IR spectrum of compound 16, vibrations observed at νas-1557 and νs-1449 cm-1 correspond to the stretching of bidentate bridging COO- groups. The absorption peaks at 1011 and 1132 cm-1 indicate the bridging and terminal alkoxy groups.
[152]
Chapter-3
In the 13C NMR spectrum of compound 16, peak at δ 186.8 and at δ 79.87 denote CO & CH3 of acetate groups respectively. Peaks at 31.278, 33.69 ppm correspond to carbon of CH3 and at 127.771 ppm to tertiary carbon of tertiary butoxy groups. Some of the synthesized metal alkoxides are subjected to the sol-gel process for the preparation of metal oxides nanomaterials. 3.4 Metal/ mixed metal oxides Metal oxides have attracted the attention of material scientists due to their optical, electrical, mechanical and catalytic properties. Oxygen interaction with atoms of metals relates to the technical processes of corrosion, bulk oxidation, heterogeneous catalysis, and so on. Studies of these processes have laid the foundation of applications in microelectronics (gate devices and deep submicron integrated circuit technologies), photo-electronics (photoluminescence, photo-conductance, and field emission), magnetoelectronics (superconductivity and colossal magneto-resistance) and dielectrics (ferro-, piezo-, and pyro-electrics). Sol-gel chemistry has been widely developed during the past decades for the synthesis of glasses and ceramics, based on the organic polymerization of alkoxide precursors. Polymerization is initiated via hydrolysis in order to the formation of an oxide network. The molecular design of the alkoxides precursors provides a chemical control over condensation reactions allowing the synthesis of tailor made materials. Different metal oxides can be obtained depending on the hydrolysis ratio of parent and substituted alkoxides. Structural properties and relationship of alkoxide as precursors for metal oxides in sol-gel process was first observed by Klemperer et al. (Mat. Res. Soc. Proc.
[153]
Chapter-3
1990). The chemistry of alkoxides and their modified products are quite interesting in the formation of metal oxides through sol-gel process. Alumina (Al2O3) has been studied extensively due to the significant application in catalysis,
bio-medical,
electro-technology,
CD/DVD
polishing,
fabrication
of
superconducting devices, electronic and ceramic industries. Various processes have been employed for the preparation of high quality alumina including the sol-gel processing of aluminum alkoxides. Advantages of sol-gel route for the synthesis of alumina in comparison to the conventional routes is well established which include high surface area, purity, narrow size particles and pore distribution. Aluminum alkoxides are very sensitive to the moisture and in order to be used as a precursor for the preparation of alumina, chelating agents are required to control hydrolysis, condensation and improve quality of alumina. The coordination number of aluminum in aluminum alkoxides increases by introducing the chelating agents and consequently the rate of hydrolysis as well as condensation decreases that reflects on the properties of final materials. In present work we have synthesized metal oxides from modified alkoxide precursors via sol-gel process. The alumina powders have been obtained by the parent alkoxide Al(OPri)3 and it’s modified compounds.
These have also been prepared by some
modified products of Al(OBut)3. The Al2O3 powders have been characterized by powder X-ray diffraction (PXRD) and their average particle sizes are calculated from Scherrer Formula.
d = (0.9)λ / β Cos θ Where d = Inter planer spacing (distance) β = FWHM (full width at half maximum) θ = Angle λ = Wave length [154]
Chapter-3
On heat treatment alumina transforms in to different phases as shown: γ
δ
θ
α- Al2O3
The stability of the δ and θ-phases are meager and these phases coexist with the parent phase γ - Al2O3. γ - Al2O3 partially transforms to the θ-phase. These transformations are simply written as γ
α- Al2O3. These phases are the prominent one, which are
also of technical interest. γ - Al2O3 has cubic crystal system and α- Al2O3 is found in trigonal crystal system with octahedral coordination geometry.
Schematic representation of synthesis of alumina from aluminum alkoxides:
[155]
Chapter-3
Alumina prepared via sol-gel process by Al(OPri)3 were calcined at 300, 500, 900 and 1200 oC for 5h to give four samples. The results of PXRD (Figure 31) are matched with the JCPDS database [22]. When the raw powder was annealed at 300o C for 5h, no crystalline phase was observed. However, when the powders were subjected to 500o C and above, the average grain sizes as calculated by the Scherrer formula were found to be 23.89, 43.5 and 59.3 nm respectively. (a)
(b) (111)
o
300 C, 5h
O
C, 5h
Intensity
Intensity
500
(220)
20
40
10
60
2 Theta
20
30
40
50
60
70
2 Theta
(c)
(d) o
O
900
1200 C, 5h C, 5h
(113)
(300)
(012)
(110)
10
20
Intensity/ a.u.
Intensity (a. u.)
(104)
30
40
2 Theta
(024)
50
60
70
10
20
30
40
50
60
2 Theta
Figure 31: PXRD of Al2O3 powder obtained from Al(OPri)3, treated at 300 (a), 500 (b), 900 (c) and 1200 (d) ⁰C for 5 h.
[156]
70
Chapter-3
The raw powder obtained from Al(OPri)2(MCA) annealed at 500, 900 and 1200⁰C for 5 h, gave XRD patterns as shown in figure 32 a, b, and c respectively. The typical particle sizes calculated from XRD data were 15.27, 59.66 and 66.24 nm respectively. Therefore the modification by MCA leads to smaller particles than the parent alkoxide when annealed at 500⁰C temperature. (a)
(b)
Intensity / a. u.
o
10
500 C, 5h o
Intensity
900 C, 5h
20
30
40
50
60
70
10
20
30
2 Theta
40
50
60
2 Theta
(c) O
Intensity/a. u.
1200 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 32: PXRD of Al2O3 obtained from Al(OPri)2(MCA), treated at (a) 500, (b) 900 and (c) 1200 ⁰C for 5 h.
[157]
70
Chapter-3
When the sol gel derived powder obtained from Al(OPr i)2(DCA) was annealed at 500, 900 and 1200 ⁰C for 5 h (Figure 33 a, b, and c), the average particle sizes intended from XRDs were found to be 20.83, 30.56 and 42.79 nm respectively. Therefore, modification of Al(OPri)3 by DCA leads much different grain sizes than the parent and the MCA modified alkoxide. (a)
(b)
o
o
10
20
30
40
50
60
900 C, 5h
Intensity
Intensity
500 C, 5h
70
10
20
30
2 Theta
40
50
60
70
2 Theta
(c)
o
Intensity/ a.u.
1200 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 33: PXRD of Al2O3 obtained from Al(OPri)2(DCA), treated at (a) 500⁰C, (b) 900 ⁰C and (c) 1200 ⁰C for 5 h.
[158]
Chapter-3
The unrefined crush of Al(OPri)2(TCA) when calcined at 500, 900 and 1200 ⁰C for 5 h gave the XRD patterns as shown in figure 34 (a, b, and c). The typical particle sizes as calculated from XRDs were 14.82, 21.64 and 51.64 nm respectively. (a)
(b) o
Intensity/ a.u.
900 C, 5h
o
10
20
30
40
50
Intensity/ a.u.
500 C, 5h
60
70
10
20
30
40
50
60
2 Theta
2 Theta
(c)
o
Intensity/ a.u.
1200 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 34: PXRD of Al2O3 obtained from Al(OPri)2(TCA), treated at (a) 500⁰C, (b) 900 ⁰C and (c) 1200 ⁰C for 5 h.
[159]
70
Chapter-3
Alumina powders were also synthesized from the gel of Al(OBu t)2(DCA) and heated at 500, 900 and 1200 ⁰C for 5 h (Figure 35 a, b, and c). The average primary particle sizes were found to be 16.16, 21.26 and 24.48 nm respectively as calculated from XRD data. (a)
(b) o
500 C, 5h o
Intensity/ a.u.
Intensity/ a.u.
900 C, 5h
10
20
30
40
50
60
10
70
20
30
40
50
60
2 Theta
2 Theta
(c)
o
Intensity/ a.u.
1200 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 35: PXRD of Al2O3 obtained from Al(OBut)2(DCA), treated at (a) 500 ⁰C, (b) 900 ⁰C and (c) 1200 ⁰C for 5 h.
[160]
70
Chapter-3
When the solid obtained from sol-gel treatment of Ca2 Al5(O)2(OAc)3(OBut)12 were annealed at 500 and 900 ⁰C for 5 h (Figure 36 a and b) an oxide of the composition CaAl2.5O4.75 was obtained as indicated by JCPDS no. 53-191. The typical particle sizes as calculated from XRD were 17.87and 22.55 nm respectively.
Intensity/ a.u.
(a)
o
500 C, 5h
10
20
30
40
50
60
70
2 Theta
(b)
o
Intensity/ a.u.
900 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 36: CaAl2.5O4.75 obtained from Ca2 Al5(O)2(OAc)3(OBut)12 treated at (a) 500⁰C and (b) 900 ⁰C for 5 h.
[161]
Chapter-3
Raw MgAl2.5O4.75 obtained from gel of Mg2 Al5(O)2(OAc)3(OBut)12 heated at 500, 900 and 1200 ⁰C for 5 h (Figure 37 a, b and c) as indicated by JCPDS no. 75-1796. The typical average particle sizes as calculated from XRD were 16.13, 27.15 and 41.97 nm respectively. (a)
(b)
o
900 C, 5h
o
Intensity/ a.u.
Intensity/ a.u.
500 C, 5h
10
20
30
40
50
60
70
10
20
30
2 Theta
40
50
60
70
2 Theta
(c) o
Intensity/ a.u.
1200 C, 5h
10
20
30
40
50
60
70
2 Theta
Figure 37: MgAl2.5O4.75 obtained from Mg2 Al5(O)2(OAc)3(OBut)12 treated at (a) 500 ⁰C, (b) 900 ⁰C and (c) 1200 ⁰C for 5 h.
[162]
Chapter-3
Experimental All experiments were performed under nitrogen/argon atmosphere by using standard Schlenk techniques for preparation of alkoxides. Reagent grade toluene was distilled over sodium under nitrogen prior to use. Monochoroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), acetylacetone (acac) and 3-chloroacetylacetone were degassed and dried over molecular sieves. [Al(OPri)3]4 and [Al(OBut)3]2 were vacuum distilled prior to use. All NMR spectra were obtained on either JEOL AL-300 FT-NMR or JEOL DELTA_NMR-300 spectrometer. 1H NMR spectra were recorded at 270 MHz and 300 MHz.
13
C NMR at 67.93 MHz and chemical shifts are given in parts per million (ppm)
relative to Me4Si.
27
Al NMR spectra were recorded at 70.39 MHz and are reference to
aqueous Al(NO3)3. A FT-IR-1600 Perkin Elmer PE machine was used for recording the infrared spectra of the compounds as Nujol mulls between NaCl plates. X-ray data collection of compounds was carried out using 'Oxford XCalibur' diffractometer with a CCD area detector using MoKα-radiation. The structure was solved by direct methods and refined through full-matrix least-squares techniques using the WINGX, SHELX-97 programs. Aluminum analysis was done by standard procedure with 8-hydroxyquinoline [23]. Alkoxy group analysis: The method is based upon the oxidation of ethanol and isopropanol according to the following example:
C2H5OH (CH3)CHOH
CH3COOH
H2O
(CH3)2CO H2O
1/2O2 [163]
Chapter-3
The sample was added to 5mL of standard chromic acid (normal potassium dichromic prepared in 12.5% sulphuric acid) in a closed small flask. After allowing the content of the flask to stand for 2 hs at the room temperature, it was transferred to the solution of Na2HCO3 and HCl (to provide an atmosphere of CO2). The liberated I2 was titrated against standard solution of sodium thiosulphate (N/5) [24].
Where V = volume (mL) of thiosulphate solution used in the analysis; N = normality of sodium thiosulphate solution; M = molecular weight of alkoxyl group; and W = weight (gram) of the sample. Synthesis of Al(OPri)2(O2CCH2Cl) (1) : A toluene (15 mL) solution of monochloroacetic acid (ClCH2CO2H) (0.94g, 10 mmol) was added dropwise to a toluene solution Al(OPri)3 (2.04g, 10 mmol) (15 mL) and strirred for 8 h at ambient temperature. The reaction mixture was stirred for 8 hs at room temperature. Compound 1 was obtained as colorless white solid (Crude = 97%) after evaporation of the solvent in vacuum. The so obtained white solid was purified by re-dissolving and crystallizing in toluene upon storage at 30oC (Crystallization yield = 83.4%). FT-IR (Nujol): ν = 1579 (νas CO2), 1465 (νs CO2), 1354 (gem-Me2 of OPri), 1176 (terminal OPri), 1072 (bridging) OPri) cm-1. 1H NMR (C6D6) δ 4.373 (sept, 1 OCHMe2), 4.373 (sep, 1 OCHMe2), 2.108 (s, ClCH2CO2), 1.678 (d, JHH O CHMe2). 13C NMR (CDCl3) δ 64.244 and 63.17 (OCHMe2), 21.438 & 23.135 (CH3), 198.3(CO).
27
Al NMR (C6D6) δ 66.35 (4 coordinated Al), 4.62 and 13.16
(s, 6
coordinated Al). Anal calcd (%) for compound 1 Al, 11.3; OPri, 49.5. Found: Al, 11.00; OPri, 48.9.
[164]
Chapter-3
Synthesis of Al(OPri)(O2CCH2Cl)2 (2) : A toluene (20 mL) solution of Al(OPri)3 (2.65g, 13 mmol) was treated dropwise with a toluene solution (20 mL) of monochloroacetic acid (ClCH2CO2H) (2.45g, 26 mmol) and left for stirring for 8 h at room temperature. After that the solvent was removed in vacuum to yield white solid (Crude = 97.3%) that was purified by re-crystallization from toluene (Crystallization yield = 88.1%) upon storage at -30oC. Compound 2 was obtained as colorless white solid upon storage at -30oC. FT-IR (Nujol): ν = 1580 (νas CO2), 1460 (νs CO2); 1640 (νas CO2), 1457 (νs CO2), 1345 (gemMe2 of OPri), 1061 (bridging OPri) cm-1. 1H NMR (C6D6) δ 3.64 (sep, 1 OCHMe2), 2.108 (s, ClCH2CO2), 0.94 (d, JHH O CHMe2). 27Al NMR (C6D6) δ 61.34 (4-5 coordinated Al). Anal. Calcd. (%) for compound 2 Al, 9.88; OPri, 49.50. Found: Al, 9.83; OPri, 48.90. Synthesis of Al(OPri)2(O2CCHCl2) (3) : A toluene (20 mL) solution of Al(OPri)3 (3.05g, 15 mmol) was treated dropwise with a toluene solution (25 mL) of dichloroacetic acid (Cl2CHCO2H) (1.42g, 15 mmol) and stirred for 8 h at room temperature. Then the solvent was removed in vacuum to give white solid (Crude = 98%). White solid was purified by re-crystallization from toluene upon storage at -10oC (Crystallization yield = 86.6%). FTIR (Nujol): ν = 1589 (νas CO2), 1468(νs CO2); 1372(gem-Me2 of OPri), 1118 (terminal OPri), 1018 (bridging OPri) cm-1. 1H NMR (CDCl3) δ 4.279, 4.257 (sep, OCHMe2), 2.344 (s, Cl2CHCO2), 1.085 (d, JHH O CHMe2). 13C NMR (CDCl3) δ 195.4 (CO), 77.54, 66.66 and 63.07 (OCHMe2), 27.74 & 25.57 (OCHMe2). Anal calcd (%) for compound 3 Al, 9.88; OPri, 43.27. Found: Al, 9.7; OPri, 42.8. Synthesis of Al(OPri)(O2CCHCl2)2 (4) : To the toluene (20 mL) solution of Al(OPri)3 (2.45g, 12 mmol) was added a toluene solution (25 mL) of dichloroacetic acid (Cl2CHCO2H) (3.09g, 24 mmol) dropwise and left for stirring at ambient temperature for [165]
Chapter-3
8 h. Then the solvent was removed in vacuum to give yellow solid (Crude = 97.8%). It was purified by re-crystallization from toluene upon storage at 0oC (Crystallization yield=80.8%). FT-IR (Nujol): ν = 1578 (νas CO2), 1465 (νs CO2); 1669 (νas CO2), 1459 (νs CO2), 1340 (gem-Me2 of OiPr), 1022 (bridging OPri) cm
_1
. 1H NMR (CDCl3) δ
4.036 (sep, OCHMe2), 2.283 (s, Cl2CHCO2), 1.181, 1.253 (d, JHH O CHMe2). 27Al NMR (C6D6) δ 64.1 (4-5 coordinated Al). Anal calcd (%) for compound 4 Al, 7.89; OPri, 17.28. Found: Al, 7.57; OPri, 17.11. Synthesis of Al(OPri)2(O2CCCl3) (5) : A toluene (20 mL) solution of trichloroacetic acid (Cl3CCO2H) (1.63g, 10 mmol) was added to the toluene solution (25 mL) of Al(OPri)3 (2.04g, 10 mmol). The reaction mixture was stirred for 8 hs. Removal of the solvent under vacuum yielded white powder (yield = 99%), which was purified by recrystallization from toluene upon storage at 0oC (Crystallization yield = 94.4%). FT-IR (Nujol): ν = 1587 (νas CO2), 1474 (νs CO2); 1350 (gem-Me2 of OPri), 1017 (bridging OPri) and 1164 (terminal OPri) cm-1. 1H NMR (CDCl3) δ 4.046 (sep, 1 OCHMe2) and 1.123 (d, JHH O CHMe2). 13C NMR (CDCl3) δ 187.98 (CO), 77.451 (OCHMe2), 33.539 & 127.771 (OCHMe2).
27
Al NMR (C6D6) δ 65.7 (4-5 coordinated Al) and 6.5ppm (6
coordinated Al). Anal calcd (%) for compound 5 Al, 8.77; OPri, 38.69. Found: Al, 8.69; OPri, 38.27. Synthesis of Al(OPri)(O2CCCl3)2 (6) : To the toluene (20 mL) solution of Al(OPri)3 (3.26g, 16 mmol) was added a toluene solution (25 mL) of dichloroacetic acid (Cl2CHCO2H) (5.22g, 32 mmol) dropwise. It was stirred for 8 hs at room temperature. After that solvent was removed in vacuum to give yellow solid (Crude = 95.0%). It was purified by re-crystallization from toluene upon storage at -30oC (Crystallization yield = [166]
Chapter-3
90.8%). FT-IR (Nujol): ν = 1582 (νas CO2), 1462 (νs CO2); 1645 (νas CO2), 1461 (νs CO2), 1355(gem-Me2 of OPri), 1032 (bridging OPri) cm-1. 1H NMR (CDCl3) δ 3.942 (sep, 1 OCHMe2) and 0.977 (d, JHH O CHMe2).27Al NMR (C6D6) δ 59.1 (4-5 coordinated Al). Anal calcd (%) for compound 6 Al, 6.57; OPri, 14.48. Found: Al, 6.60; OPri, 14.43. Synthesis of Al(OBu t)2(O2CCHCl2) (7): To the solution of Al(OBu t)3 (2.46g, 10 mmol) in toluene (20 mL) was added toluene solution (20 mL) of dichloroacetic acid (Cl2CHCO2H) (1.27g, 10 mmol) dropwise and stirred for 8 h.. Then the solvent was removed in vacuum to give white solid (Crude = 96.0%), which was purified by recrystallization from toluene (Crystallization yield = 91.2%) upon storage at -30oC. FT-IR (Nujol): ν = 1580 (νas CO2), 1462 (νs CO2); 1108 (bridging OBu t) and 920 (terminal OBut) cm _1. 1H NMR (C6D6) δ 2.108 (s, Cl2CHCO2), 1.47, 1.39 (s, OCMe3). 13C NMR (C6D6) δ 199.3 (acid CO), 68.66 (acid CH3), 33.53, 33.69, 31.27, 30.91 (OBut).
27
Al
NMR (C6D6) δ 62.59 (4-5 coordinated Al) and 11.03 (6 coordinated Al). Anal. Calcd. (%) for compound 7 Al, 8.96. Found: Al, 8.88. Synthesis of Al(OBut)(O2CCHCl2)2 (8): A toluene (20 mL) solution of dichloroacetic acid (Cl2CHCO2H) (2.8g, 22 mmol) was added dropwise to a toluene solution (20 mL) of Al(OBut)3 (2.7g, 11 mmol). After stirring for 8 h at ambient temperature the reaction mixture was concentrated in vacuum to give white solid (Crude=97.1%), which was purified by re-crystallization from toluene upon storage at -30oC (Crystallization yield=88.2%). FT-IR (Nujol): ν = 1568 (νas CO2), 1445 (νs CO2); 1677 (νas CO2), 1439 (νs CO2), 1099 (bridging OBut) cm-1. 1H NMR (C6D6) δ 2.107 (s, Cl2CHCO2), 1.047, 0.292 (s, OCMe3).
13
C NMR (C6D6) δ 201.45 (acid CO), 66.651 (acid CH3), 31.7 &
[167]
Chapter-3
127.786 (OCMe3).
27
Al NMR (C6D6) δ 59.2 (4-5 coordinated Al). Anal calcd (%) for
compound 8 Al, 7.58; Found: Al, 7.55. Synthesis of Al(OBut)2(O2CCCl3) (9): To the solution of Al(OBut)3 (3.45g, 14 mmol) in toluene (25 mL) was added toluene solution (20 mL) of trichloroacetic acid (Cl3CCO2H) (2.28g, 14 mmol) dropwise and stirred for 8 h at room temperature. Then the solvent was removed under reduced pressure to give white solid (Crude=97.8%). It was purified by re-crystallization at 0oC (Crystallization yield=90.8%). FT-IR (Nujol): ν = 1615 (νas CO2), 1460 (νs CO2); 1108 (bridging OBut) and 920 (terminal OBut) cm-1. 1H NMR (C6D6) δ 1.47, 1.42, 1.38, 1.05 (s, OCMe3). 13C NMR (C6D6) δ 68.72 (acid CCl3), 33.70, 31.27, 31.04, 30.88 (OCMe3).
13
C NMR (C6D6) δ 200.7 (acid CO), 75.91 (acid CH3),
31.7 and 127.786 (OCMe3).27Al NMR (C6D6) δ 64.79 (4-5 coordinated Al) and 6.11 (6 coordinated Al). Anal calcd (%) for compound 9 Al, 8.04; Found: Al, 7.90. Synthesis of Al(OBut)(O2CCCl3)2 (10): A flask was charged with Al(OBut)3 (3.32g, 13.5 mmol) in toluene (20 mL).To it a toluene solution (20 mL) of trichloroacetic acid (Cl3CCO2H) (4.41g, 27 mmol) was added dropwise and left for stirring for 8 h. Removal of solvent in vacuum yielded white solid (Crude = 98.4%), that was re-crystallized in toluene at 0oC (Crystallization yield = 93.0%). FT-IR (Nujol): ν = 1538 (νas CO2), 1434 (νs CO2); 1696 (νas CO2), 1459 (νs CO2); 1128 (bridging OBut) cm-1. 1H NMR (C6D6) δ 1.46, 1.28, 1.12 (s, OCMe3). 13C NMR (C6D6) δ 195.3 (acid CO), 78.56 (acid CCl3) and 30.84 &128.137 (OCMe3).
27
Al NMR (C6D6) δ 58.19 (4-5 coordinated Al) and 11.7 (6
coordinated Al). Anal calcd (%) for compound 10 Al, 6.35; Found: Al, 6.22. Synthesis of Al(CH3COCHCOCH3)3 (11): A toluene (18 mL) solution of 3chloroacetylacetone (CH3COCHCOCH3) (1.10g, 11 mmol) was added dropwise to the [168]
Chapter-3
toluene solution (20 mL) of Al(OPri)3 (2.24g, 11 mmol) and the reaction mixture was stirred at 85⁰C for 24 h. It was left at room temperature for 24 h to yield colorless crystals.
1
H NMR (C6D6) δ 5.53, 5.42 (s, CH3OCCHCOCH3) and 1.83 (s,
CH3OCCHCOCH3). 13C NMR (C6D6) δ 193.2 (CO), 68.89 (acac-CH2) and 101.00 (CH3acac). One of the crystals of compound 11 was characterized by X-ray crystallography. Synthesis of Al(CH3COCClCOCH3)3 (12): To the toluene (18 mL) solution of Al(OBut)3 (2.46g, 10 mmol) was added a toluene solution (20 mL) of 3-chloroacetylacetone (CH3COCHClCOCH3) (1.34g, 10 mmol) dropwise and stirred at reflux temperature for 24 h. After the completion of reaction it was cooled to room temperature. Compound 12 was obtained as colorless crystals at room temperature after 24 h. 1H NMR (C6D6) δ 1.69 (s, CH3OCC(Cl)COCH3).
13
C NMR (C6D6) δ 188.34 (CO) and 99.8 (CH3-Clacac). One
of the crystals was characterized by single crystal X-ray crystallography. Synthesis of Mg2Al5(OPri)12(0Ac)3(O)2 (13): A toluene (22 mL) solution of magnesium acetate (H3CCO2)2Mg (1.28g, 9 mmol) was added to the solution of Al(OPri)3 (3.67g, 18 mmol) in toluene(18 mL) slowly. After stirring at refluxing for 8 h, the solution was filtered, concentration upto 10 mL and kept at -20 ⁰C but it did not crystallize. Then it was dried in vacuum to give white viscous liquid (Crude = 97.9%). FT-IR (Nujol): ν = 1696 (νas CO2), 1459 (νs CO2); 1357 (gem-CMe2), 1112 (terminal OPri) and1078 (bridging OPri) cm-1.
13
C NMR (C6D6) δ 201.09 (CO of Ac), 80.21 (OAc), 26.572,
27.840, (OCHMe2), 66.33 (C of CH3).
1
H NMR (C6D6) δ 4.221 (sept. OPri3), 3.505 (s,
CH3CO2), 1.213 (d, JHH O CHMe2). 27Al NMR (C6D6) δ 63.022 (4-5 coordinated Al) and 4.590 (6 coordinated Al). Anal calcd (%) for compound 13 Al, 12.24; OPri, 64.35. Found: Al, 12.0; OPri, 64.02. [169]
Chapter-3
Synthesis of Ca2Al5(OPri)12(0Ac)3(O)2 (14): A toluene (25 mL) solution of calcium acetate (H3CCO2)2Ca (1.73g, 11 mmol) was added to a toluene solution (25 mL) of Al(OPri)3 (4.49g, 22 mmol) dropwise at room temperature and stirred at 100⁰C for 8 h. After cooling to room temperature, it was filtered and concentrated up to 10 mL and kept at -10 ⁰C for crystallization. However, when no crystallization took place the solvent was removed in vacuum to give white viscous liquid (Crude = 97.9%). FT-IR (Nujol): ν = 1538 (νas CO2), 1434 (νs CO2); 1349 (gem-CMe2), 1131 (terminal OPri) and1012 (bridging OPri) cm-1.
13
C NMR (C6D6) δ 193.00 (CO of Ac), 79.14 (OAc), 26.557,
27.84, (OCHMe2), 63.488 (C of CH3).
1
H NMR (C6D6) δ 4.417 (sept. OPri3), 3.399 (s,
CH3CO2), 1.677, 1.404 (d, JHH O CHMe2).
27
Al NMR (C6D6) δ 65.678 (4-5 coordinated
Al) and 4.5 (6 coordinated Al). Anal calcd (%) for compound 14 Al, 11.9; OPri, 62.35. Found: Al, 11.0; OPri, 60.03. Synthesis of Mg2Al5(OBut)12(0Ac)3(O)2 (15): To the clear solution of Al(OBut)3 (4.18g, 17 mmol) in toluene (20 mL) was added toluene solution (20 mL) of magnesium acetate (H3CCO2)2Mg (1.21g, 8.5 mmol) dropwise and stirred at 100 ⁰C for 8 h. After cooling to room temperature, it was filtered and concentrated upto 10 mL and kept at -25 ⁰C. Then the solvent was removed in vacuum to give yellow viscous liquid (Crude = 97.94%). FTIR (Nujol): ν = 1578 (νas CO2), 1466 (νs CO2); 951 (terminal OBu t) and1091 (bridging OBut) cm
_1
.
13
C NMR (C6D6) δ 199.8 (CO of Ac), 77.67 (OAc), 31.278, 33.830
(OCMe3), 127.71 (C of CH3). 1H NMR (C6D6) δ 1.421 (s, OAc), 1.155 (s, OCMe3). 27Al NMR (C6D6) δ 52.398 (4-5 coordinated Al). Anal calcd (%) for compound 15 Al, 10.36; Found: Al, 10.13.
[170]
Chapter-3
Synthesis of Ca2Al5(OBut)12(0Ac)3(O)2 (16): To the toluene (25 mL) solution of Al(OBut)3 (4.67g, 19 mmol) was added dropwise a toluene solution (25 mL) of calcium acetate (H3CCO2)2Ca (1.50g, 9.5 mmol) and stirred at room temperature. The reaction mixture was heated slowly by raising the bath temperature to 100 ⁰C. The reaction mixture, after filtration, was concentrated upto 5 mL and kept at -20 ⁰C for crystallization. When no crystal formation took place, the solvent was removed in vacuum to give white viscous liquid (Crude=98.9%). FT-IR (Nujol): ν = 1648 (νas CO2), 1548 (νs CO2); 910 (terminal OBut) and1101 (bridging OBut) cm-1.
13
C NMR (C6D6) δ
186.8 (CO of Ac), 79.87 (OAc), 31.278, 33.694, (OCMe3), 127.771 (C of CH3).
1
H
NMR (C6D6) δ 1.419, 1.462 (s, OAc), 1.102 (s, OCMe3). 27Al NMR (C6D6) δ 52.398 (4-5 coordinated Al). Anal calcd (%) for compound 16 Al, 10.36; Found: Al, 10.13. General method of synthesis of alumina (Al2O3) from parent/modified alkoxides: To the concentrated solution of parent / modified alkoxide in dry THF was added double distilled water in 1:0.1 molar ratio. After sol-gel process the obtained gel was dried in oven to get raw powder that was subjected to different temperatures and durations in the furnace for calcination. These treated powders were examined by powder X-ray diffraction (PXRD). Synthesis of MgAl2.5O4.75 /CaAl2.5O4.75 from modified alkoxides: The herometallic alkoxide in THF was treated with double distilled water in 1: 0.1 molar ratio. After solgel process the obtained gel was dried in oven to get off white powder (raw). Raw powder was subjected to different temperatures and durations in the furnace. The sizes of the newly prepared crystalline powders were examined by powder X-ray diffraction (PXRD). [171]
Chapter-3
References
[1] (a) Bradley, D.C., Mehrotra, R.C., and Wardlaw, W., J. Chem. Soc. (1952) 4204 (b) Mehrotra R.C., J. Indian Chem. Soc., 31 (1954) 904 [2]
Gainsford, G.J., KemmitT., Lensik, C., and Milestone, N.B., Inorg. Chem., 34 (1995) 746.
[3]
Mehrotra, R.C. and Bohra, R., Metal Carboxylates, Academic Press, London (1983)
[4] (a) Mehrotra, R.C., Gaur, D.P., and Bohra, R., Metal β-Diketonates and Allied Derivatives, Academic Press, London (1978) (b) Mehrotra, R.C., In Recent Trends in Inorganic Chemistry (A. Chakravorty ed.), 256–275, Indian National Science Academy Publications (1986). [5]
K. Narasaka, Synthesis, (1993) 1
[6] (a) Turova, N. Ya., Kozunov, V. A, Yanovskii, A. I., Bokii, N. G., Struchkov, Yu. T., Tamopolskii, B. L., J. Inorg. Nucl. Chem., 41 (1979) 5. (b) Folting, K., Streib, W. E., Caulton, K. G., Poncelet, Hubert- Pfalzgraf, L. G., Polyhedron 10 (1991) 1639. [7]
Jain, A. K., Bohra, R. , Mehrotra, R. C., Nagar, S., Sharma S., Heteroatom Chemistry 14, 6 (2003) 518
[8]
Yamamoto, H. and Saito, S., Pure Appl. Chem., 71(1999) 239
[9]
Mehrotra, R.C. and Gupta, V.D., J. Organomet. Chem., 4 (1965) 237
[10]
Bradley, D.C., Mehrotra, R.C., Wardlaw, W., J. Chem. Soc. (1952) 2027
[11] (a) Wengrovius, J. H., Carbauskas, M. F., Williams, E. A., Going, R. C., Donahue, [172]
Chapter-3
P. E., and Smitb, J. F., J. Am. Chem. Soc. 108 (1986) 982 (b) Shirodker, M, Broker, V., Nather, C, Bensch, W and Rane, K. S., Ind. Journal of Chemistry, 49A (2010) 1607 [12]
Zhou S, Antonietti and Niederberger M, Small, 3 (2007) 763
[13]
Smolentsev, A. I., Zherikova, K. V., Trusov, M. S., Stabnikov, P. A., D. Naumov Yu., and Borisov, S. V., Journal of Structural Chemistry, 52, 6 (2011) 1070
[14]
Mehrotra, R. C., Singh, A, and Sogani, Sanjeev, Chem. Rev., 94 (1994) 1643
[15]
Mishra, S. and Singh, A., Transition Metal Chemistry 27 (2002) 541
[16]
Teff , D. J., Huffman, J. C., and Caulton, K. G., Inorg. Chem., 35 (1996) 2981
[17]
Bochmann, M., Wilkinson, G., Young, G.B., Hursthouse, M.B., and Malik, K.M.A., J. Chem. Soc., Dalton Trans., (1980) 1863
[18]
Turevskaya, E.P., Berdyev, D.V., Turova, N.Ya., Starikova, Z.A., Yanovsky, A.I., Struchkov, Yu.T. and Belokon, A.I., Polyhedron, 16 (1997) 663
[19]
Boulmaaz, S., Papiernik, R., and Hubert-Pfalzgraf, L.G., Chem. Mater., 3 (1991) 779
[20]
Mehrotra, R.C., Coord. Chem., (IUPAC), 21(1981) 113
[21]
Pandey, A., Gupta, V. D., and Nöth, H., Eur. J. Inorg. Chem. (1999) 1291
[22]
http://www.icdd.com/products/pdf4.htm
[23]
Svhela, G., Vogel’s Textbook of Micro and Semimicro Quantitative Inorganic Analysis, Fifth Edition, (1978) 250
[24]
Bradley, D. C., F. Halim, M. A., Wardlaw, W., J. Chem. Soc. (1950) 3450
[173]
CHAPTER 4 Synthesis & Characterization of TiO2 films by Titanium butoxide [Ti(OBun)4] and it’s modified precursors
[174]
Chapter-4
Titamium alkoxide are highly reactive towards water than silicon alkoxides, because of lower electronegativity of titanium compared to silicon. Metal alkoxide acting as lewis acid, can interact with compound having lone pairs of electron to achieve an increased coordination number, which is called coordination expansion. The chemistry of organically modified titanium alkoxide precursors (and metal alkoxide precursors in general) is more demanding than that of the silicon based organo-functional precursors. The synthesis and characterization of nano-materials (nanotubes, nanorods, nanowires and nanosheets) have received substantial attention due to their unique properties and novel applications [1]. Most of the work has been concentrated on the important metal oxides such as TiO2, SnO2, VO2, and ZnO. Among them, TiO2 and TiO2-derived materials are of importance for their use in solar cells as well as in environmental purification. For example, TiO2 has been used as an electron receptor in dye-sensitized solar cells, as water treatment material, as catalyst, as gas sensors, and so on [2, 3]. In the field of alternative energy, a dye-sensitized solar cell is now a scorching topic due to its high conversion efficiency produced with a porous TiO2 electrode that is composed of nanometer-sized particles [4]. A low cost, large area photovoltaic device was introduced by Grätzel and coworkers [5] in 1990. The conversion of solar energy to electrical energy entails a wide band gap n-type metal oxide semiconductor whose conduction band edge lies at a redox level to accept an electron from photoexcited dye. Functional properties of TiO 2 are influenced by many factors such as crystallinity, size and surface area [6]. The shape and size of inorganic nanoparticles are controlled by using conventional synthesis methods such as the sol–gel method, hydrothermal method, molecular beam expitaxy and metal-organic chemical vapour deposition [7, 8]. Controlling the shape and
[175]
Chapter-4
size of inorganic nanoparticles with the introduction of surfactants has been recently developed [9]. A number of different shapes, including rod-, arrow-, teardrop-, tetrapodand disk-shape, of nanoparticles were prepared by introducing surfactants during preparation [10-12]. Sol-gel method is a size-tailoring technique and has been widely used for the preparation of nanocrystalline matrials including TiO2, SnO2 and ZrO2 [1315]. Modifications of precursors have been reported to influence the morphology of resulting metal oxide particle [16]. The replacement of one or more alkoxy groups by mono, bi and multidentate ligand has several chemical and structural consequences for sol-gel processing such as: (i) the degree of crosslinking of the gel network is decreased. (ii) The substitution of monodentate alkoxy groups by bi or multidentate ligands favors the formation of gel instead of crystalline precipitate. (iii) The polarity change by the organic groups has probably a similar effect on the network structure as changing the polarity of the solvent. (iv) The complexing ligands may stereochemically direct the hydrolysis and condensation reaction because the site trans to an organic group has a different reactivity than the cis site. In this context, the different modified precursors of titanium n-butoxide have been used to synthesize TiO2 thin film on conductive glass plate by using a single-step sol-gel technique. The surface morphology of the thin films of titania nanoparticles were controlled by using different precursors and film preparation technique. Scanning electron microscopy (SEM) and X-ray diffraction techniques have been used to examine the surface morphologies. X-ray crystallography was used to characterize single crystal structure of the modified precursors 1 & 2, which were obtained by the reaction of
[176]
Chapter-4
Ti(OBun)4 with dichloroacetic acid (DCA) & trichloroacetic acid (TCA) respectively in 1:2 molar ratio.
Figure 1: Schematic diagram for preparation of TiO2 films 4.1 Synthesis and characterization of Ti(OBun)2(OOCCHCl2)2: Titanium tetrabutoxide was reacted with dichloroacetic acid in 1:2 molar ratio at ambient temperature in toluene. After the removal of solvent under reduced pressure a viscous liquid was obtained in quantitative yield. The composition of the compound was found to be Ti(OBun)2(OOCCHCl2)2 by analytical and spectroscopic analyses. It was left for crystallization at -30°C for 48 h to give colourless crystals of Ti6 (μ2-O)2(μ3-O)2(μ2OC4H9)2 (OC4H9)6(OOHCCCl2)8 (1). [177]
Chapter-4
Ti(OC4H9)4 + HOOCCHCl2
Ti(OC4H9)2(OOCCHCl2)2 + 2 C4H9OH
6Ti(OC4H9)2(OOCCHCl2)2
Ti6O4(OC4H9)8(OOCCHCl2)2 + 4CCl3COOC4H9 (1)
4.2 Synthesis and characterization of Ti(OBun)2(OOCCCl3)2: In order to obtain the trichloroacetate substituted product of titanium tetra-butoxide, another reaction was carried out with trichloroacetic acid in 1:2 molar ratio under the same reaction condition. After removal of the solvent under the vacuum a light-yellow viscous liquid corresponding to composition Ti(OBun)2(OOCCCl3)2 (2) was obtained. It was left for crystallization at -30°C for 48 hs to give colourless crystals. The
structure
of
crystal
was
proven
to
be
Ti6(μ2-O)2(μ3-O)2(μ2-OC4H9)2
(OC4H9)6(OOCCCl3)8 (2) by X-ray analysis. The formation of the product 2 can be schematised by the following reactions: Ti(OC4H9)4 + HOOCCCl3
6Ti(OC4H9)2(OOCCCl3)2
Ti(OC4H9)2(OOCCCl3)2 + 2 C4H9OH
Ti6O4(OC4H9)8(OOCCCl3)2 + 4CCl3 COOC4H9 (2)
The crystal structure of compound 1 was already reported [17]. Compound 2 crystallizes in the monoclinic space group P21/n with Z = 4. The molecular structure (Figure 2) consists of a hexanuclear unit of the formula Ti6O4(OC4H9)8(OOCCCl3)8. Each molecule possesses crystallographic inversion symmetry in the crystal and contains six titanium atoms all being hexa-coordinated. In the structure of this hexanuclear complex, there are two Ti2O10 units linked to two corner-sharing octahedra with the help of four bridging oxygen atoms: two triply bridging (μ3-oxo) O4 and O*4 and two doubly bridging O2 and [178]
Chapter-4
O*2. In the structure all the trichloroacetate groups are bridged bidentately while the butoxy groups are of two types. Out of the eight butoxy groups six are present at terminal positions and two (O17 and O*17) are occupying bridging positions. Although all six titanium atoms are bonded to triply bridging oxygen atoms they have non-equivalent environments. Ti16 is attached to two oxygen atoms of terminal butoxy groups, one oxygen atom of the bridging butoxy group shared with Ti1 and two oxygen atoms in cis position of the bridging acetate group. Ti1 is connected to one oxygen atom of the bridging butoxy group (shared with Ti16), three oxygen atoms of the trichloroacetate groups at equatorial positions, and one μ2-oxo ligand, while Ti5 has three oxygen atoms of the acetate groups in facial positions, one oxygen atom of the terminal butoxy group, and one doubly bridging oxygen atom (with Ti1) (Figure 3).
Figure 2: Ball and Stick representation of the molecular structure of 2
[179]
Chapter-4
Figure 3: Titanium-oxygen molecular core of complex 2
Table 1 Crystal data of compound 2
Chemical Formula Formula Weight Crystal System Space Group a [Å] b [Å] c [Å] α [°] β [°] γ [°] V [Å3] Z
C24 H36 Cl12 O14 Ti3 1441.58 Monoclinic P 21/n 14.971(5) 16.174(5) 19.443(5) 90 105.856(5) 90 4528.82 4
The important bond lengths and bond angles for complex 2 are listed in table 2 and 3, respectively. All the torsion angles of complex are given in table 4.
[180]
Chapter-4
Table 2 Selected bond lengths (Å) for 2 Atoms Ti1-O21 Ti1-O2 Ti1-O17 Ti1-O36 Ti5-Ti16 Ti5-O31 Ti5-O65 Ti16-O19 Ti16-O58 Ti16-O4
Length 2.066(3) 1.770(3) 2.025(3) 2.093(3) 3.6582(13) 2.175(3) 1.769(3) 2.218(4) 1.783(4) 2.131(3)
Atoms Ti1-O4 Ti1-Ti16 Ti1-O30 Ti5-O2 Ti5-O8 Ti5-O34 Ti16-O15 Ti16-O17 Ti16-O60 Ti5-O4
Length 1.843(3) 3.0680(12) 2.065(3) 1.832(3) 2.041(3) 2.105(3) 2.070(3) 1.973(3) 1.766(3) 1.964(3)
Table 3 Selected bond angles (deg.) for 2. Atoms O21-Ti1-O4 O4-Ti1-O2 O4-Ti1-O17 O21-Ti1-O30 O2-Ti1-O30 O21-Ti1-O36 O2-Ti1-O36 O4-Ti5-O2 O4-Ti5-O8 O4-Ti5-O31 O8-Ti5-O31 O2-Ti5-O34 O31-Ti5-O34 O19-Ti16-O4 O4-Ti16-O15 O4-Ti16-O17 O19-Ti16-O58 O15-Ti16-O58 O4-Ti16-O60
Bond angle 95.97(13) 104.88(13) 80.72(13) 166.87(13) 92.67(13) 83.40(14) 90.24(13) 97.16(13) 89.72(13) 84.06(13) 79.95(14) 88.96(13) 82.17(14) 82.88(13) 87.10(12) 75.26(12) 169.51(15) 93.20(16) 165.30(16)
Atoms O21-Ti1-O2 O21-Ti1-O17 O2-Ti1-O17 O4-Ti1-O30 O17-Ti1-O30 O4-Ti1-O36 O17-Ti1-O36 O4-Ti5-Ti16 O2-Ti5-O8 O2-Ti5-O31 O4-Ti5-O34 O8-Ti5-O34 O4-Ti5-O65 O19-Ti16-O15 O19-Ti16-O17 O15-Ti16-O17 O4-Ti16-O58 O19-Ti16-O60 O15-Ti16-O60 [181]
Bond angle 90.82(14) 86.77(13) 174.12(13) 95.36(13) 88.52(13) 164.88(13) 84.16(12) 27.90(8) 163.94(14) 86.33(13) 64.54(14) 80.99(13) 101.26(14) 77.28(15) 84.60(13) 156.15(14) 92.35(14) 83.97(16) 96.39(15)
Chapter-4
In general, the titanium oxygen bond lengths range from 1.766 to 2.218
(average bond
lengths 1.992 ). The Ti O bonds of the terminal butoxy groups are short (average 1.766 ), and the corresponding Ti O C angles are rather large (142.4 160.4°). onger Ti O bonds (Ti16 O19 = 2.218
and Ti16 O4 = 2.131 ) are due to the trans
influence of the opposite bonds. The Ti O bond lengths of the bridging butoxy groups are comparatively longer (Ti1 O17 = 2.025 (3) and Ti16 O17 = 1.973 (3)
) with
corresponding smaller angles (Ti1 O17 C49 =129.5 (3) and Ti16 O17 C49 = 127.2 (3)°. The sum of the angles around μ3-O is 360° making the perfectly planar configuration.
Table 4: Torsion angles of compound 2 Atom1 O17 O30 O36 O21 O4 O2 O2 O30 O30 O36 O36 O21 O21 O4 O4 O2 O17 O36 O21 O4 O2
Atom2 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1
Atom3 O2 O2 O2 O2 O2 O17 O17 O17 O17 O17 O17 O17 O17 O17 O17 O30 O30 O30 O30 O30 O36 [182]
Atom4 Ti5 Ti5 Ti5 Ti5 Ti5 Ti16 C49 Ti16 C49 Ti16 C49 Ti16 C49 Ti16 C49 C29 C29 C29 C29 C29 C35
Torsion 57(1) -44.9(3) 39.0(3) 122.4(3) -141.2(2) 149(1) -12(1) -109.5(1) 89.7(3) 166.5(1) 5.7(3) 82.8(1) -78.0(3) -13.8(1) -174.6(3) 23.5(4) -150.8(4) -66.5(4) -81.8(7) 128.7(4) -5.9(4)
Chapter-4
O17 O30 O21 O4 O2 O17 O30 O36 O4 O2 O2 O17 O17 O30 O30 O36 O36 O21 O21 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti16 Ti16 Ti16 Ti16 Ti16 Ti5 Ti5 Ti5 Ti5 Ti5
Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 Ti1 O2 O2 O2 O2 O2 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4
O36 O36 O36 O36 O21 O21 O21 O21 O21 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti1 Ti1 Ti1 Ti1 Ti1 [183]
C35 C35 C35 C35 C20 C20 C20 C20 C20 Ti16 Ti5 Ti16 Ti5 Ti16 Ti5 Ti16 Ti5 Ti16 Ti5 O4 O8 O31 O34 O65 O2 O8 O31 O34 O65 O2 O8 O31 O34 O65 O2 O17 O30 O36 O21
175.9(4) 86.7(4) -96.7(4) 174.8(5) 140.7(4) -44.6(4) -113.8(6) -129.1(4) 35.7(4) -165.4(1) 34.6(2) 12.8(1) -147.3(2) 100.4(1) -59.7(2) 13.8(6) -146.3(4) -72.9(1) 127.0(2) 123.4(3) 8.6(7) 39.9(3) -42.3(3) -134.6(3) -0.1(2) 165.4(2) 85.5(2) 112.6(5) -96.2(2) 155.3(2) -39.2(2) -119.1(2) -92.0(5) 59.1(2) -34.6(2) 147.3(2) 59.7(2) 146.3(4) -127.0(2)
Chapter-4
Ti16 Ti16 Ti16 Ti16 Ti16 Ti5 Ti5 Ti5 Ti5 Ti5 Ti1 Ti1 Ti1 Ti1 Ti1 O2 O4 O31 O34 O65 O2 O4 O8 O34 O65 O2 O4 O8 O31 O65 O2 O4 O8 O31 O34 Ti5 Ti5 O8 O8
O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 O4 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 Ti5 O8 O8 C9 C9
Ti1 Ti1 Ti1 Ti1 Ti1 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 O8 O8 O8 O8 O8 O31 O31 O31 O31 O31 O34 O34 O34 O34 O34 O65 O65 O65 O65 O65 C9 C9 C10 C10 [184]
O2 O17 O30 O36 O21 O15 O17 O58 O60 O19 O15 O17 O58 O60 O19 C9 C9 C9 C9 C9 C29 C29 C29 C29 C29 C35 C35 C35 C35 C35 C66 C66 C66 C66 C66 C10 O15 Cl11 Cl13
165.4(1) -12.8(1) -100.4(1) -13.8(6) 72.9(1) 48.8(2) -147.4(2) -44.3(2) 153.0(5) 126.3(2) -150.4(1) 13.4(1) 116.5(2) -46.2(7) -72.9(1) 114.8(6) -1.0(4) 83.0(4) 166.6(4) -102.3(4) -12.5(4) -110.1(4) 159.1(4) 76.9(4) 87(2) 16.2(4) -97.5(6) -151.2(4) -70.2(4) 110.8(4) -7.6(6) 90.6(6) -178.0(6) -107(1) -96.8(6) -156.5(4) 22.4(8) 1.0(6) 122.6(4)
Chapter-4
O8 O15 O15 O15 O8 C10 C9 C9 C9 C9 C9 O58 O58 O60 O60 O19 O19 O4 O4 O15 O15 O17 O60 O19 O4 O15 O17 O58 O19 O4 O15 O17 O58 O60 O4 O15 O17 O17 O58
C9 C9 C9 C9 C9 C9 O15 O15 O15 O15 O15 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16
C10 C10 C10 C10 O15 O15 Ti16 Ti16 Ti16 Ti16 Ti16 O17 O17 O17 O17 O17 O17 O17 O17 O17 O17 O58 O58 O58 O58 O58 O60 O60 O60 O60 O60 O19 O19 O19 O19 O19 O4 O4 O4 [185]
Cl14 Cl11 Cl13 Cl14 Ti16 Ti16 O4 O17 O58 O60 O19 Ti1 C49 Ti1 C49 Ti1 C49 Ti1 C49 Ti1 C49 C59 C59 C59 C59 C59 C33 C33 C33 C33 C33 C20 C20 C20 C20 C20 Ti1 Ti5 Ti1
-119.6(4) -178.1(4) -56.4(5) 61.4(5) -0.5(7) 178.4(3) -28.6(4) -70.5(5) 63.6(4) 165.7(4) -111.9(4) 101.1(2) -97.5(3) -155.1(2) 6.3(3) -71.9(1) 89.6(3) 12.2(1) 173.6(3) -31.4(4) 130.0(4) 157(1) 57(1) -65(2) -127(1) -40(1) 72.1(9) 177.3(9) -11.7(9) 15(1) -88.1(9) 26.5(4) -112.7(8) 124.2(4) -49.2(4) -137.8(4) -13.4(1) 147.4(2) -116.5(2)
Chapter-4
O58 O60 O60 O19 O19 O15 O15 O17 O58 O60 O19 O4 Ti1 Ti1 Ti1 Ti16 Ti16 Ti16 Cl25 Cl25 Cl44 Cl44 Cl46 Cl46 C27 O31 C27 O30 Ti5 Ti5 O34 C39 O34 O34 O34 O36 O36 O36 O17
Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 Ti16 O17 O17 O17 O17 O17 O17 C27 C27 C27 C27 C27 C27 C29 C29 C29 C29 O34 O34 C35 C35 C35 C35 C35 C35 C35 C35 C49
O4 O4 O4 O4 O4 O4 O4 O15 O15 O15 O15 O15 C49 C49 C49 C49 C49 C49 C29 C29 C29 C29 C29 C29 O30 O30 O31 O31 C35 C35 O36 O36 C39 C39 C39 C39 C39 C39 C51 [186]
Ti5 Ti1 Ti5 Ti1 Ti5 Ti1 Ti5 C9 C9 C9 C9 C9 C51 H491 H492 C51 H491 H492 O30 O31 O30 O31 O30 O31 Ti1 Ti1 Ti5 Ti5 O36 C39 Ti1 Ti1 Cl40 Cl42 Cl69 Cl40 Cl42 Cl69 C52
44.3(2) 46.2(7) -153.0(5) 72.9(1) -126.3(2) 150.4(1) -48.8(2) 70.5(5) -63.6(4) -165.7(4) 111.9(4) 28.6(4) -91.2(4) 148.7(3) 29.6(5) 112.8(4) -7.3(5) -126.4(3) 7.0(6) -174.9(3) -111.7(4) 66.3(5) 128.1(4) -53.8(5) 166.1(3) -11.6(7) -172.6(3) 5.2(7) 2.4(7) -177.8(3) -9.3(7) 170.9(3) -119.1(4) 122.8(4) 2.5(6) 60.7(5) -57.5(5) -177.7(3) -62.4(6)
Chapter-4
O17 O17 H491 H491 H491 H492 H492 H492 C49 C49 C49 H511 H511 H511 H512 H512 H512 C51 C51 C51 H521 H521 H521 H522 H522 H522 Ti16 Ti16 Ti16 O58 O58 O58 H591 H591 H591 H592 H592 H592 Ti16
C49 C49 C49 C49 C49 C49 C49 C49 C51 C51 C51 C51 C51 C51 C51 C51 C51 C52 C52 C52 C52 C52 C52 C52 C52 C52 O58 O58 O58 C59 C59 C59 C59 C59 C59 C59 C59 C59 O60
C51 C51 C51 C51 C51 C51 C51 C51 C52 C52 C52 C52 C52 C52 C52 C52 C52 C73 C73 C73 C73 C73 C73 C73 C73 C73 C59 C59 C59 C6 C6 C6 C6 C6 C6 C6 C6 C6 C33 [187]
H511 H512 C52 H511 H512 C52 H511 H512 C73 H521 H522 C73 H521 H522 C73 H521 H522 H731 H732 H733 H731 H732 H733 H731 H732 H733 C6 H591 H592 C2 H61 H62 C2 H61 H62 C2 H61 H62 C25
177.3(4) 59.4(6) 57.8(6) -62.5(6) 179.6(5) 177.3(5) 57.0(6) -60.9(6) -64.9(7) 177.1(5) 56.6(8) 54.8(8) -63.2(8) 176.3(6) 173.6(6) 55.6(8) -64.9(8) -179.6(6) -60.3(9) 58.6(9) -60.4(9) 58.9(9) 177.8(7) 58.7(9) 178.0(7) -63.1(9) -32(2) -151.3(9) 87(2) 176(1) -62(1) 56(1) -64(2) 58(1) 176(1) 57(2) 179(1) -63(1) 133.9(7)
Chapter-4
Ti16 Ti16 Ti5 Ti5 Ti5 O65 O65 O65 H661 H661 H661 H662 H662 H662 C66 C66 C66 H701 H701 H701 H702 H702 H702 C70 C70 C70 H711 H711 H711 H712 H712 H712 C46 C46 C46 H231 H231 H231 H232
O60 O60 O65 O65 O65 C66 C66 C66 C66 C66 C66 C66 C66 C66 C70 C70 C70 C70 C70 C70 C70 C70 C70 C71 C71 C71 C71 C71 C71 C71 C71 C71 C23 C23 C23 C23 C23 C23 C23
C33 C33 C66 C66 C66 C70 C70 C70 C70 C70 C70 C70 C70 C70 C71 C71 C71 C71 C71 C71 C71 C71 C71 C24 C24 C24 C24 C24 C24 C24 C24 C24 C25 C25 C25 C25 C25 C25 C25 [188]
H331 H332 C70 H661 H662 C71 H701 H702 C71 H701 H702 C71 H701 H702 C24 H711 H712 C24 H711 H712 C24 H711 H712 H241 H242 H243 H241 H242 H243 H241 H242 H243 C33 H251 H252 C33 H251 H252 C33
-107.2(9) 18(1) 130.7(5) 10.3(9) -108.0(6) -57.3(8) -178.1(5) 62.3(8) 63.0(8) -57.8(8) -177.4(6) -178.2(6) 61.1(8) -58.5(8) -169.9(7) -50.0(9) 69.5(8) -48.1(9) 71.7(8) -168.8(7) 70.0(9) -170.1(7) -50.6(9) -179.0(8) 60(1) -59(1) 61(1) -60(1) -178.5(8) -59(1) -179.8(8) 61(1) -86(1) 32(1) 157.7(9) 153.0(8) -89(1) 37(1) 35(1)
Chapter-4
H232 H232 C25 C25 C25 H231 H231 H231 H232 H232 H232 C23 C23 C23 H251 H251 H251 H252 H252 H252 H11 H11 H11 H12 H12 H12 H13 H13 H13 C1 C1 C1 H21 H21 H21 H22 H22 H22 Ti16
C23 C23 C23 C23 C23 C23 C23 C23 C23 C23 C23 C25 C25 C25 C25 C25 C25 C25 C25 C25 C1 C1 C1 C1 C1 C1 C1 C1 C1 C2 C2 C2 C2 C2 C2 C2 C2 C2 O19
C25 C25 C46 C46 C46 C46 C46 C46 C46 C46 C46 C33 C33 C33 C33 C33 C33 C33 C33 C33 C2 C2 C2 C2 C2 C2 C2 C2 C2 C6 C6 C6 C6 C6 C6 C6 C6 C6 C20 [189]
H251 H252 H461 H462 H463 H461 H462 H463 H461 H462 H463 O60 H331 H332 O60 H331 H332 O60 H331 H332 C6 H21 H22 C6 H21 H22 C6 H21 H22 C59 H61 H62 C59 H61 H62 C59 H61 H62 O21
152.8(9) -81(1) -173.6(9) -53(1) 66(1) -53(1) 68(1) -173.2(9) 66(1) -173.2(9) -54(1) -61(1) 178.2(8) 58(1) 178.8(7) 58(1) -62(1) 59(1) -62(1) 178.0(8) -170(1) -54(2) 75(2) -51(1) 66(2) -165(1) 70(1) -174(1) -45(2) 179(1) 55(1) -59(1) 62(2) -62(1) -176(1) -63(2) 174(1) 60(1) 15.0(8)
Chapter-4
Ti16 O19 C22 O19 O19 O19 O21 O21 O21 O4
O19 C20 C20 C20 C20 C20 C20 C20 C20 Ti1
C20 O21 O21 C22 C22 C22 C22 C22 C22 O2
C22 Ti1 Ti1 Cl23 Cl47 Cl48 Cl23 Cl47 Cl48 Ti5
-162.2(3) -2.9(7) 174.3(3) 80.0(5) -39.5(6) -158.7(4) -97.5(5) 142.9(4) 23.8(6) 141.2(2)
4.3 Influence of different precursor chemistry on TiO 2 film morphology It is well known in sol-gel chemistry, the precursor influences the hydrolysis and the condensation kinetics and, thus, the final thin film morphology. In the present study, two different derivatives of carboxylic acid have been used i.e. dichloroacetic acid and trichloroacetic acid to substitute butoxy group of parent precursor Ti(OBu n)4 to control the size and morphology of metal oxides nanoparticles. In both cases, the products were in form of oligomer, which was contrary to titanium butoxide, which is monomer. The presence of oligomer is known to slow down the rate of condensation reaction. Experiments [18] show that the hydrolysis of such modified precursors lead to more monodispersed
and
smaller
nanopaticles.
Substituting
trichloroacetate
and
dichloroacetate groups for the butoxy moiety decrease the particle size of titania nanoparticles moderately.
[190]
Chapter-4
The smaller the particle, the more pronounced Ostwald ripening effect. The remarkable difference in the SEM images between the three samples can be explained by the modification of titanium butoxide with DCA and TCA. In case of compound 1 and 2, cubic shaped nanoparticles with different particle sizes were obtained as shown in figure 4, but in case of Ti(OBu n)4, uniform nanoparticles were obtained. The particle size observed from SEM analysis was also confirmed by XRD analysis (Figure 5).
After calcination at 450°C, anatase and rutile both phases of titania were detected. Size of the particle was estimated by Scherrer’s formula.
D = kλ/β cos θ
(3)
Where k is Scherrer constant, λ indicates wavelength of the X-ray, β is half width and θ indicates the Bragg diffraction angle. The value of λ is 1.5406 Å.
[191]
Chapter-4
The
grain
size
of
TiO2
in
thin
films
synthesized
from
(Ti(OBun)4,
Ti(OBun)2(OOCCHCl2)2 and Ti(OBun)2(OOCCCl3)2 were 26 nm, 22 nm and 18.6 nm (Figure 4).
(a)
(b)
(c)
Figure 4: XRD of the TiO2 thin film obtained from Ti(OBu)n4 (a), Ti(OBun)2(OOCCHCl2)2 (b) and Ti(OBun)2(OOCCCl3)2 (c) [192]
Chapter-4
(a)
(b)
(c)
Figure 5: SEM micrograph of TiO2 thin film prepared by dip coating technique from Ti(OBu)n4 (a), Ti(OBun)2(OOCCHCl2)2 (b) and Ti(OBun)2(OOCCCl3)2 (c)
(a)
(b)
(c)
Figure 6: SEM micrograph of TiO2 thin film prepared by spin coating technique from Ti(OBu)n4 (a), Ti(OBun)2(OOCCHCl2)2 (b) and Ti(OBun)2(OOCCCl3)2 (c)
4.4 Effect of deposition techniques As substrate for TiO2 thin films, F: SnO2 glass (2 cm X 2 cm) glass plates were chosen. The thin films were prepared by using dip and spin coating techniques and characterized by SEM. In dip coating technique, after optimizing the dipping and lifting speed, dipping length and waiting time, electrodes of fine layer were obtained by using sols of different precursors. Spin coated thin films were prepared at 3000 rpm for 3 min. The SEM
[193]
Chapter-4
analyses of thin films prepared by both above mentioned techniques reveals that the particle size of thin films prepared by spin coating technique was more uniform than the films prepared by dip coating technique as shown in fig. 4 and 5. The TiO2 thin film obtained by using spin coating technique may be used as a good electrode material for photovoltaic application. The results obtained by in present work reveal that the surface morphology of the thin films depends not only on the modified precursors but also on the deposition technique. Compared with most other metals, the structural chemistry of titanium alkoxide is simpler, because the coordination of titanium in stable compounds is mostly six sometime five, but rarely larger than six. This makes an elaboration of structural principles easier. By modifying the titanium butoxide with dichloroacetic acid and trichloroacetic acid, the degree of crosslinking of the gel network is decreased, because of the smaller proportion of hydrolysable OR groups, which produce smaller nanoparticles. The rutile thin film of TiO2 prepared by the spin coating technique has uniform, nonaggregated nanosized particles. So, the TiO2 thin film prepared in this work by using spin coating technique from compound 2 at pH 2 may have good potential for photovoltaic application. We hope that, by using this type of molecular approach, we can further improve our photoelectrodes, which is needed for high-power applications.
[194]
Chapter-4
Experimental section: The manipulations pertaining to the syntheses of compound 1 and compound 2 were performed under dry argon atmosphere using the Schlenk techniques [17]. Ti(OBun)4 (Aldrich Chemicals) was used as such for carrying out the reactions. Toluene and CDCl3 were dried by standard procedures. Conductive glass plates of Solaronix (Switzerland). 1
H NMR spectra were recorded in CDCl3 on a Bruker Biospin ARX 300 MHz
spectrometer with tetramethylsilane as internal reference at 243 K. Titanium was gravimetrically estimated as TiO2. A Jasco FT-IR-5300 spectrometer was used for recording the infrared spectra of the compounds as Nujol mulls between NaCl plates. X-ray diffraction analyses of the thin films were performed on a Tecnai 20 G2 X-ray diffractometer using a Cu Kα radiation. The samples were scanned over a range of 10° – 90°. The secondary particle sizes of different TiO2 nanoparticles were measured by Nanotrac particle size analyser. The surface morphology of samples was studied by the scanning electron microscopy on quanta 200 SEM. X-ray data collection of compound 2 was carried out using a 'Oxford XCalibur' diffractometer with a CCD area detector using MoKα-radiation. The structure was solved by direct methods and refined through full-matrix least-squares techniques using the WINGX, SHELX-97 programs. The thin films of titania were prepared by using dip coater and spin coater of Apex instruments company, Kolkata, India.
[195]
Chapter-4
Synthesis of Ti6(μ2-O)2(μ3-O)2(μ2-OC4H9)6(OOCHCl2)8 (1): A solution of CHCl2COOH (0.8486 g, 6.61mmol) in toluene (20 ml) was added dropwise to a stirred solution of Ti(OBun)4 (1.12 g, 3.29 mmol ) in toluene (30mL) over 30 min at 25°C. After complete addition, stirring of the reaction mixture was continued for 10 h. Then all the solvent was removed in vacuo to give a viscous liquid (1.394 g, 94%), which is kept for crystallization at -30 0C for 48 hs after dissolving the liquid in 10 ml of toluene. 1H NMR (25 0C): δ = 4.12, 4.23, 4.44 4.54 (t, OCH2 of OBun); 1.33, 1.45, 1.51 (m, CH2 of OBun); 1.10, 1.21 (t, CH3 of OBun); 5.85, 5.94, 6.15 (s, CHCl2 of acid). FT-IR (Nujol): ν = 2904 ν(CH), ∼1000 ν (C-O), 1760 νas (CO2), 1350 νs (CO2), 1588 νas (CO2), 1440 νs (CO2) cm−1. Synthesis of Ti6(μ2-O)2(μ3-O)2(μ2-OC4H9)2 (OC4H9)6(OOCCCl3)8 (2): A solution of CCl3 COOH (1.4882 g, 9.05mmol) in toluene (20 ml) was added dropwise to a stirred solution of Ti(OBun)4 (1.55 g, 4.55mmol ) in toluene (30mL) over 30 min at 25°C. After complete addition, stirring of the reaction mixture was continued for 10 h. Then all the solvent was removed in vacuo to give a viscous liquid (2.021 g, 89%), which is kept for the crystallization at -30 0C for 48 hs after dissolving in 10 ml of toluene. 0
1
H NMR (25
C): δ = 4.34, 4.37, 4.39 (t, OCH2 of OBun of bridging butoxide); 3.66, 3.68, 3.70 (t,
OCH2 of OBun of terminal butoxide); 1.33, 1.78 (m, CH2 of OBun); 0.962, 0.973, 0.997 (t, CH3 of OBun). FT-IR (Nujol): ν = 2910 ν (C-H), ∼1005 ν (CO), 1755 νas (CO2), 1344 νs (CO2), 1593 νas (CO2), 1445 νs (CO2) cm−1.
[196]
Chapter-4
Synthesis of colloidal TiO2 Nanoparticles: Titanium dioxide was synthesized by sol-gel method. TiO2 was synthesized by adding of double distilled water (27.77 mm ) of pH = 2 (adjusted by conc. HCl) to 0.668 g of the three different precursors Ti(OBu n)4, compound 1 and compound 2 dissolved in 3.0 mL of THF. In the Ti(OBun)4 white precipitate was formed instantaneously while yellow precipitates were formed with precursors 2 and 3. To prevent cracking during film drying, polyethylene glycol (PEG, molecular weight 8000) and triton-100 (molecular weight 625) were added in proportion of 30% of the TiO2 weight in the remaining solution. A small amount of gel (without binders) was kept in oven at 100 0C for 12 h to get the dried powder of TiO2 nanoparticle for making suspension to analyse secondary particle size.
Preparation of TiO2 thin film: The so obtained suspension of TiO2 from different precursors were used for deposition of the film on a FTO glass (2cm X 2cm) by dip coating technique using 90 mm/min of dipping and lifting speed for 5 times (dipping length of plate is 4 mm, waiting time is 0.3 min. and drying time is 0.1 min). Spin coating technique was also used for deposition of the layer of TiO 2 on substrate at 3000 rpm for 3 minutes. The layers were dried in air at room temperature for 10 min, followed by treatment at 50°C for 15 min. Then, the films were annealed at 450°C for 30 minutes.
[197]
Chapter-4
References [1] (a) Murray, C. B., Kagan, C. R., Bawendi, M. G., Annu. Rev. Mater. Sci. 30 (2000) 545 (b) Alivisatos, A. P., Science 271 (1996) 933 (c) Brus, L., J. Phys. Chem. 98 (1994) 3575 (d) Bawendi, M. G., Steigerwald, M. L., Brus, L., Annu. Rev. Phys. Chem. 41(1990) 477 [2]
Chun, K. Y., Park, B. W., Sung, Y. M., Kwak, D. J., Hyun, Y.T., Park, M. W., Thin Solid Films 517 (2009) 4196
[3]
Sebastián, P. J., Olea, A., Campos, J., Toledo, J. A., Gamboa, S. A., Sol. Energy Mater. Sol. Cells. 81 (2004) 349
[4]
Rao, C. N. R., Nath, M., Dalton Trans. (2003) 1-24
[5]
Patzke, G. R., Krumeich, F., Nesper, R., Chem. Int. Ed. 41(2002) 2446
[6]
Ishizaki, K., Komarneni, S., Nanko, M. K., Academic Publishers, Chapter 1, 4, 5 (1998)
[7]
Mele, G., Del Sole, R., Vasapollo, G., J. Catal. 217 (2003) 334
[8]
Petroski, J. M., Wang, Z. L., Green, T. C., J. Phys. Chem. B 102 (1998) 3316
[9]
Pileni, M. P., Nat. Mater. 2 (2003) 145
[10]
Vidal-Iglesias, F. J., Solla-Gullon, J., Aldaz, A., Electrochem. Commun. 6 (2004) 1080
[11]
Lee, J. H., Leu, I. C., Hon, M. H., J. Phys. Chem. B 109 27 (2005) 13056
[12]
Mills, A., Elliot, N., Parkin, I. P., J. Photochem. Photobio. A: Chem. 151 (2002) 171
[13]
Chang, S. M., Doong, R. A.,J. Phys. Chem. B 108 (2004) 18098 [198]
Chapter-4
[14]
Tsai, H. C., Doong, R. A., Anal. Biochem. 334 (2004) 183
[15]
Chang, S.M., Doong, R. A., J. Phys. Chem. B 110 (2006) 20808
[16]
Barbe C J, Arendse F, Comte P, Jirousck M, Lenzmann F, Shklover V, Gratzel M J. Am. Ceram. Soc. 80 [12] (1997) 3157
[17]
Pandey, A., Pandey, A., Singh, S., Mayer, P., Parak, W. J., Z. Naturforsch 65b (2010) 147
[18]
Sanchez, C., Babonneau, F., Doeuff, S., Leaustic, A., Ceramic Ultrastructure and Pocessing, Wiley (1988) 77
[199]
