Transition Met Chem (2008) 33:775–779 DOI 10.1007/s11243-008-9110-y
The ONN-complexes of dioxomolybdenum(VI) with dibasic 2-hydroxy-1-naphthaldehyde S-methyl/allyl-4-phenyl-thiosemicarbazones _ Irfan Kızılcıklı Æ Songu¨l Eg˘lence Æ Ali Gelir Æ ¨ lku¨seven Bahri U
Received: 10 March 2008 / Accepted: 14 May 2008 / Published online: 10 June 2008 Ó Springer Science+Business Media B.V. 2008
Abstract New dioxomolybdenum(VI) complexes were prepared by reacting S-methyl/allyl-4-phenyl-thiosemicarbazones of 2-hydroxy-1-naphthaldehyde (L1H2 and L2H2) and [MoO2(acac)2] in methyl, ethyl and propylalcohols. In the complexes the doubly deprotonated ligands are coordinated to molybdenum as tridentate ONN-donors through phenolic-oxygen, azomethine- and thioamide-nitrogen. The solid complexes of general formula [MoO2L(ROH)] which contain an alcohol (ROH) as second ligand were characterized by physico-chemical and spectroscopic methods. The fluorescence emission intensities of the compounds were recorded in chloroform, and the intensity changes were evaluated depending on chelation and time. The structure of the S-allyl-4-phenyl-thiosemicarbazone complex has been determined by the single crystal X-ray diffraction method.
Introduction Thiosemicarbazones and their metal complexes have raised considerable interest in pharmacology due to their wide range of biological activities such as antitumour [1–4], Electronic supplementary material The online version of this article (doi:10.1007/s11243-008-9110-y) contains supplementary material, which is available to authorized users. _ Kızılcıklı S. Eg˘lence B. U ¨ lku¨seven (&) I. Department of Chemistry, Istanbul University, Avcilar, Istanbul 34320, Turkey e-mail:
[email protected] A. Gelir Department of Physics, Istanbul Technical University, Maslak, Istanbul 34469, Turkey
antiviral [5–7], antifungal [8, 9], antimalarial [10] and antioxidant properties [11]. In addition to these, investigations on the interactions of thiosemicarbazones and DNA have received significant attention over the last years [12–14]. Molybdenum is an oligo-element and one of cofactors for several enzymes catalysing redox reactions [15], and some molybdenum compounds are included in plausible enzyme model systems [16, 17]. The known molybdenum (VI) complexes of thiosemicarbazones of general formula [MoO2L(L0 )] are potential catalysts as the coordinated L0 molecule may be replaced by the activated enzyme molecule. 2-Hydroxy-arilydene-thiosemicarbazones act by ON1N4 or ON1S donor sets in the octahedral dioxomolybdenum(VI) complexes. Therefore, in preparation of these complexes the sulphur [18–20] or N4-nitrogen [21–25] substitued thiosemicarbazone derivatives (–N4H2–SR or –N4HR–SH) have been used to supply the coordination of the thioamide-nitrogen (N4) or sulphur atoms along with phenolic-oxygen and azomethine-nitrogen (N1). In our previous paper, we reported the first dioxomolybdenum(VI) complexes which have two substituents both on sulphur and thioamide-nitrogen of the thiosemicarbazone ligand [26]. In this work, we present new dioxomolybdenum(VI) complexes with dianionic forms of the S-methyl/allyl-N4-phenyl-thiosemicarbazones, L1H2 and L2H2 (Fig. 1). The ligands and complexes were characterized by elemental analysis, molar conductivity, IR and 1 H-NMR spectroscopy. The structure of [MoO2(L2) C2H5OH] (V) was determined by X-ray single-crystal diffraction method. The fluorescence spectra of the ligands and complexes were recorded in chloroform, and the intensity changes of the molybdenum complexes were monitored for 4 days.
123
776
Transition Met Chem (2008) 33:775–779
Alcohol O
O O Mo 4 N 1 N 2
N
S R
Fig. 1 The molybdenum chelates of S-R-N4-phenyl-thiosemicarbazones. R/Alcohol = CH3/CH3OH(I); CH3/C2H5OH(II); CH3/C3H7OH(III); C3H5/CH3OH(IV); C3H5/C2H5OH (V); C3H5/ C3H7OH(VI)
Experimental Materials and methods Analytical data were obtained with a Thermo Finnigan Flash EA 1112 analyser. Infrared spectra were recorded as KBr discs on a Mattson 1000 FT-IR spectrophotometer in the 4000–400 cm-1 range at room temperature. Electronic spectra were recorded in CHCl3 solution with a ATIUnicam Spectrometer in the 800–200 nm range. Fluorescence emission measurements were made on a LS 50 Perkin-Elmer spectrofluorophotometer using 1-cm quartz cells and slit width of 10 nm depending on samples. The 1 H-NMR spectra were recorded on Bruker Avance-500 model spectrometer relative to SiMe4 using deutered CHCl3 as solvent. X-ray measurements were made on a Rigaku RAXIS RAPID imaging plate area detector with graphite mono˚ ). The data were chromated MoKa radiation (k = 0.71073 A corrected for Lorentz and polarization effects. An empirical absorption correction was applied which resulted in transmission factors ranging from 0.79 to 1.00. The molecular and crystal structures were solved by direct methods implemented in the program SIR92 [27]. Hydrogen atoms were refined using the riding model and the non-hydrogen atoms were refined anisotropically. All calculations were performed using the Crystal Structure crystallographic software package [28, 29]. Preparation of the ligands 2-Hydroxy-1-naphthaldehyde S-R-4-phenyl-thiosemicarbazones [where R = methyl (L1H2) or R = allyl (L2H2)] and MoO2(acac)2 were prepared with small modifications of general methods [30, 31]. The colour, m.p. (°C), yield (%), elemental analysis, UV–Vis [kmax (loge), nm (dm3 cm-1 mol-1)], IR (cm-1) and 1H-NMR (ppm) data of the ligands were as follows. L1H2: light yellow, 155, 80. Analytical data for C19H17N3OS (335.42 g mol-1), found (calc.): C, 68.0 (68.3); H, 5.1 (4.9); N, 12.5 (11.3); S, 9.6 (9.3). UV–Vis:
123
241(5.19); 334(4.85); 376(4.99). IR (cm-1): m(OH) 3434(s); m(NH2) 3280(s); v(CH) 2925(w); d(NH2) 1620(s); m(C=N1) 1601(s); m(N2=C) 1566(m). 1H-NMR (ppm): 13.09, 12.64 (s, s, trans/cis isomer ratio = 2, OH), 9.37, 9.31 (s, s, syn/anti isomer ratio = 1/1, 1H, CH=N1), 8.09– 7.12 (doublet and triplets, 11H, aromatics), 6.17 (s, 1H, NH), 2.35 (s, 3H, –CH3). L2H2: light yellow, 148, 55. Anaytical data for C21H19N3OS (361.46 g mol-1), found (calc.): C, 69.8 (69.7); H, 5.3 (5.2); N, 11.6 (11.5); S, 8.9 (8.7). UV–Vis: 241(4.72); 334(4.39); 379(4.54). IR (cm-1): m(OH) 3422(s); m(NH2) 3268(s); d(NH2) 1624(s); m(C=N1) 1593(m); m(N2=C) 1582(m). 1H-NMR. (ppm): 13.15, 12.62 (s, s, cis/trans isomer ratio = 1/2, OH), 9.55, 9.32 (s, s, syn/anti isomer ratio = 1/2, 1H, CH =N1), 8.08–7.00(doublet and triplets, 11H, aromatics), 6.58 (s, 1H, NH), 6.00 (m, 1H, –CH =), 5.41, 5.38 (d, d, trans/cis isomer ratio = 2/3, 2H, =CH2), 3.72 (d, 2H, S–CH2). Preparation of [MoO2(L1)(CH3OH)] (I) 2-Hydroxy-1-naphthaldehyde S-methyl-4-phenyl thiosemicarbazone (0.34 g, 1 mmol) was dissolved in absolute methanol (5 mL) by heating. The hot solution was treated with 2 mL of a methanolic solution of MoO2(acac)2 (0.32 g, 1 mmol). The reaction mixture was stirred for 60 min, at 60 ± 2 °C, and than the mixture was allowed to stand at 5 °C for several days. The red precipitate was collected by filtration and washed twice by 2–4 mL of cold methanol. The product was dried for 12 h in air. The molybdenum complexes, II–VI, were synthesized by a similar procedure. The second ligand (alcohol), colour, m.p. (decomp., °C), yield (%), analytical and spectroscopic data of the molybdenum complexes were given as follows. (I): C1H3OH, red, 225, 70. Analytical data for C20H19N3O4SMo (493.38 g mol-1), found (calc.): C, 48.6 (48.3); H, 3.9 (3.8); N, 8.8 (8.4); S, 6.5 (6.2). UV–Vis: 244(4.52); 336(4.27); 462(3.82). IR: m(OH)alc.3460(s); v(CH) 2925(w), m(C1H3) 2929(w); d(C1H3) 1439(s). 1 H-NMR: 9.73 (s, 1H, CH=N1); 3.41 (s, 1H, C1H3), 2.49 (s, 3H, S–CH3). (II): C2H3C1H2OH, red, 277, 75. Analytical data for C21H21N3O4SMo (507.41 g mol-1), found (calc.): C, 49.7 (49.7); H, 4.2 (4.2); N, 8.3 (8.4); S, 6.3 (6.2). UV–Vis: 245(4.50); 337(4.27); 461(3.82). IR: m(OH)alc. 3395(s); m(C1H) 2968(w); d(C2H3) 1458(s); d(C1H2) 1385(m). 1 H-NMR: 9.81 (s, 1H, CH=N1), 3.73 (q, 2H, C1H2), 2.56 (s, 3H, S–CH3), 1.24 (t, 3H, C2H3). (III): C3H3C2H2C1H2OH, red, 272, 65. Analytical data for C22H23N3O4SMo (521.44 g mol-1), found (calc.): C, 50,7 (50.4); H, 4.4 (4.2); N, 8.1 (8.2); S, 6.2 (6.3). UV–Vis: 246(4.67); 339(4.44); 463(4.01). IR: m(OH)alc.3449(s);
Transition Met Chem (2008) 33:775–779
m(C1H), m(C2H) 2929, 2955(w); d(C3H3) 1458(s); d(C1H2), d(C2H2) 1385(m). 1H-NMR: 9.81 (s, 1H, CH=N1), 3.55 (t, 2H, C1H2), 2.56 (s, 3H, S–CH3), 1.51 (m, 2H, C2H2), 0.84 (t, 3H, C3H3). (IV): C1H3OH, red, 206, 75. Analytical data for C22H21N3O4SMo (519.42 g mol-1), found (calc.): C, 50.9 (51.0); H, 4.1 (4.0); N, 8.1 (8.0); S, 6.2 (5.9). UV–Vis: 243(4.81); 339(4.57); 463(4.14). IR: m(OH)alc. 3376(s); v(CH) 2971(w); d(CH3) 1451(s), d(CH2) 1435(m); 1HNMR: 9.77 (s, 1H, CH=N1), 5.98 (m, 1H, –CH =), 5.30, 5.17 (d, d, trans/cis ratio = 2/3, 2H, =CH2), 3.82 (d, 2H, S–CH2), 3.48 (s, 1H, C1H3). (V): C2H3C1H2OH, red, 209, 80, analytical data for C23H23N3O4SMo (533.45 g mol-1), found (calc.): C, 51.8 (51.9); H, 4.3 (4.4); N, 7.9 (7.8); S, 6.0 (5.8). UV–Vis: 243(4.61); 339(4.37); 464(3.94). IR: m(OH)alc. 3449(s); m(C1H) 2971(w); d(C2H3) 1451(s), d(C1H2) 1385(m). 1HNMR: 9.77 (s, 1H, CH=N1), 5.98 (m, 1H, –CH=), 5.30, 5.17 (d, d, trans/cis ratio = 1, 2H, =CH2), 3.82 (d, 2H, S–CH2), 3.71 (q, 2H, C1H2), 1.24 (t, 3H, C2H3). (VI): C3H3C2H2C1H2OH, red, 210, 60. Analytical data for C24H25N3O4SMo (547.47 g mol-1), found (calc.): C, 52.6 (52.4); H, 4.6 (4.7); N, 7.7 (7.5); S, 5.8 (5.5). UV–Vis: 245(4.46); 336(4.23); 463(3.74). IR: m(OH)alc. 3287(s); m(C1H), m(C2H) 2935, 2968(w); d(C3H3) 1451(s); d(C1H2), d(C2H2) 1385 (m). 1H-NMR: 9.65 (s, 1H, CH=N1), 5.91 (m, 1H, –CH=), 5.23, 5.10 (d, d, trans/cis ratio = 2/3, 2H, =CH2), 3.74 (d, 2H, S–CH2), 3.52 (t, 2H, C1H2), 1.51 (m, 2H, C2H2), 0.86 (t, 3H, C3H3).
Results and discussion The free ligands, obtained as crystalline powders, were soluble in alcohols and donor solvents such as DMSO. The interaction of the ligands with MoO2(acac)2 in 1:1 molar ratio in selected alcohols yielded diamagnetic complexes corresponding to the general formula [MoO2(L)ROH]. These complexes are soluble in alcohols and chlorinated hydrocarbons. The solid forms of I–VI are stable in air, but a few hours later they transform to black coloured amorphous materials at reflux temperature of solvent. IR and 1H-NMR spectra The stretching vibration bands of the OH, N4H, C=N1 and N2=C groups of the ligands were clearly observed. The S-alkyl-4-phenyl-thiosemicarbazone ligands coordinate through phenolic oxygen, azomethine (N1) and thioamide (N4) nitrogen atoms. Deprotonisations of the hydroxyl and thioamide groups, and so chelation of the L1 and L2 can be monitored by means of IR and 1H-NMR spectra.
777
In the spectra of the complexes (I–VI) the m(OH) and m(N4H) bands are absent due to coordination of the deprotonated phenolate and –N4R moieties (Fig. 1). The m(N2=C) vibrations of the ligands are shifted to higher frequencies by ca. 12–20 cm-1 while m(C=N1) is shifted by 8 cm-1 to lower frequencies by chelating, and the m(C=N1) and m(N2=C) bands of I–VI were recorded in the range of 1592–1596 cm-1 and 1578–1582 cm-1, respectively. The spectra of I–VI contain the aliphatic CH2, CH3 and OH vibrations of the coordinated ROH molecules. The characteristic bands of cis-MoO2 group are in the 888–919 and 939–942 cm-1 ranges. The ligand protons recorded the expected chemical shift values, and even the systematic signals of cis- and transisomers belonging to the S-allyl protons were observed [32]. The chemical shifts of the aromatic protons showed a pattern of obvolute doublet and triplet signals in the range of 7.18 and 8.30 ppm. In the complex spectra, there are no OH and N4H signals which can be attributed to the thiosemicarbazone moiety. The shift values of azomethine and S-alkyl protons somewhat different compared to the free ligand protons. The 1H-NMR spectra of the I–VI also contain the proton signals of CH2 and CH3 groups which are clear enough to be analysed in detail. Electronic and fluorescence spectra The electronic absorption bands of the compunds were recorded in 10-4 M chloroform solution between 200 and 600 nm. In the spectra of the ligands the p?p* transitions of the aromatic rings were recorded at 241 and 334, and the n?p* transitions of the azomethine and thioamide moieties were observed in the range of 376–379 nm. The spectra of the complexes showed the p?p* and n?p* transition bands at 241–246 and 336–339 nm, respectively. The bands at 461–463 nm indicate the charge-transfer to the lowest empty molybdenum d orbital [33, 34]. The fluorescence spectra of the compounds in 10-4 M chloroform were recorded at excitation wavelength 380 nm. The spectra of the ligands, fresh and 4 days aged solutions of the methanol bonded complexes, I and IV, are shown in Fig. 2. The S-allyl thiosemicarbazone (L2H2) showed ca. 40% higher fluorescence intensity than the S-methyl derivative (L1H2). Quenching of the fluorescence intensities of the thiosemicarbazones were observed upon chelation of the dioxomolybdenum ion. As known, when the probability of intersystem crossing (ISC) increases, the quantum yield decreases [35]. Thus, the ligands are in lower ISC probability due to the electron localization in the conjugated backbone after complexation. The fluorescence spectra of the complexes dissolved in chloroform were recorded after four days. The fluorescence intensities of the aged complexes, It and IVt, increased
123
778
Transition Met Chem (2008) 33:775–779
Fig. 2 Fluorescence spectra of the ligands (L1, L2), fresh (I, IV), and 4 days aged complex solutions (It, IVt)
with time (Fig. 2). Considering the kmax values in Fig. 2 are almost equal, it seems likely that complexes I and IV partly dissociated giving the free ligands. Structure of [MoO2(L2)(C2H5OH)] (V) Recrystalizations of I–VI were carried out in alcohol which is present as second ligand in the complex structure. By slow evaporation of the recrystalization solution relatively
large crystals can be generated. However, only crystals of V could be obtained in suitable size for single crystal diffraction method. A red platelet crystal of C23H23N3O4MoS having approximate dimensions of 0.50 9 0.20 9 0.20 mm was mounted on a glass fibre. For the crystallographic data and structure refinement parameters of the complex [MoO2(L2)C2H5OH] (V) (533.45 g mol-1): C23H23N3O4MoS, red coloured plates, triclinic, space group P-1(#2), unit cell parameters a, ˚ ; b, 11.7308(8) A ˚ ; c, 13.2486(9); a, 111.8160(2)o; 8.4932(4) A o ˚ 3; Z, 2; b, 101.0902(7) ; c, 103.0207(7)o; V, 1136.970(5) A -3 -1 Dcalc, 1.558 g cm ; l (MoKa), 0.703 nm ; F000, 544.00; 89,650 reflections collected, 6,663 unique and 6,378 observed reflections; Rint, 0.023; R [I [ 2r(I)], 0.037; R w [I [ 2r(I)], 0.033; goodness-of-fit indicator, 1.102. The relevant bond lengths and angles of the complex V are presented in Table 1, and its ORTEP drawing with the atom numbering scheme is given in Fig. 3. The bond angle of the MoO2 core indicates the cisdioxomolybdenum structure. The doubly deprotonated ligands are bonded to the cis-MoO2 coordinating through O3, N1 and N3 atoms in accordance with the IR and 1HNMR data. The fourth and fifth coordination sites of molybdenum belong to two oxo groups, and octahedral coordination of the central atom is completed by the oxygen atom of the alcohol molecule. The –CH3 group of the ethanol molecule is slightly disordered. The molybdenum centred bond distance and angle values in the [MoO2(L2)(C2H5OH)] molecule indicate that the molybdenum atom lies in three axis distorted octahedral. The distortion is especially apparent through the bond between molybdenum (Mo1) and oxygen (O4) of ethanol ˚. that is weakly coordinated with the bond distance, 2.445 A The 4-phenyl rings are in different planes according to the chelate rings due to the torsion angles of Mo1-N3-C16-C17
Table 1 The bond lengths and angle values of [MoO2(L2)C2H5OH] ˚) Bond distances (A
Angles (o)
Torsion angles (o)
Mo1–O1
1.703(1)
O1–Mo1–O2
106.54(7)
Mo1–N1–N2–12
Mo1–O2
1.690(2)
O1–Mo1–N1
156.56(7)
Mo1–N1–C11–C2
Mo1–O3
1.947(2)
O1–Mo1–N3
95.90(6)
O3–Mo1–N1–N2
161.8(1)
Mo1–O4
2.445(1)
O2–Mo1–O3
99.41(8)
N3–Mo1–N1–C11
174.1(1)
Mo1–N1
2.218(1)
O2–Mo1–N1
95.15(6)
Mo1–N3—C16–C17
Mo1–N3
2.070(2)
O2–Mo1–N3
99.25(8)
C12–N3–C16–C21
62.2(2)
O3–C1
1.328(2)
O3–Mo1–O1
103.35(6)
O3–Mo1–N3–C16
148.64(9)
C1–C2
1.393(2)
O3–Mo1–N1
81.82(5)
O1–Mo1–N3–C16
21.5(1)
C2–C11
1.442(3)
O3–Mo1–N3
148.02(5)
O1–Mo1–N1–N2
58.4(2)
C11–N1
1.294(2)
N1–Mo1–N3
71.43(5)
C11–C2–C1–C10
171.2(2)
N1–N2
1.397(2)
N2–N1–Mo1
118.13(7)
S1–C12–N2–N1
175.0(1)
N2–C12
1.317(2)
C1–O3–Mo1
133.80(1)
C12–N3
1.351(2)
C11–N1–Mo1
125.90(1)
123
3.1(2) 7.5(3)
57.0(2)
Transition Met Chem (2008) 33:775–779
779
References
Fig. 3 The ORTEP view of [MoO2(L2)C2H5OH] (V)
and C12-N3-C16-C21. In the chelate molecule, other geometric parameters are in the expected ranges (Table 1). In complex V, hydrogen bonds are formed by O1, O2, O4 and N2 atoms. The O4–H23N2 hydrogen bond dis˚ , and the pairs of these tance in the structure is 2.026 A hydrogen bonds connect two molecules as the chelate ring planes become parallel. This dimer structure repeats itself ˚ ) interactions through the propagation of O2–H14 (2.557 A ˚ ) and in vertical axis. Other interactions O1–H6 (2.709 A ˚ ), are in horizontal plane, and pairs of O1–H15 (2,622 A these contacts tie the chelate ring planes of the dimers in directions of x- and y-axis. Conclusions Chelation between 2-hydroxy-arylidene-thiosemicarbazones and MoO2 occurs by ON1S or ON1 N4 donor sets. In all studies except our previous paper [26], synthesis of these molybdenum complexes have been realized by the thisosemicarbazones with thioamide group having only one substituent (–NH2–SR or –NHR–SH). Herein, by describing new ON1N4-complexes of dioxomolybdenum(VI) with 2-hydroxy-naphthaldehyde S-methyl/allyl-4-phenylthiosemicarbazones (–NHR1–SR2) we showed again that the nitrogen atom of the N4H-Ph moiety has a coordination ability in spite of the steric bulk of the phenyl ring. Appendix. Supplementary data Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC 673245 for [MoO2(L2)C2H5OH].
1. Mantegazza P, Tommasini R (1951) Farmaco 6(2):264 2. Ainscough EW, Brodie AM, Denny WA, Finlay GJ, Ranford JD (1998) J Inorg Biochem 70(3–4):175 3. Sau DK, Butcher RJ, Chaudhuri S, Saha N (2003) Mol Cell Biochem 253(1):21 4. Padhye S, Afrasiabi Z, Sinn E, Fok J, Mehta K, Rath N (2005) Inorg Chem 44:1154 5. Mishra V, Pandeya SN, Pannecouque C, Witvrouw M, De Clercq E (2002) Arch Pharm 335(5):183 6. Genova P, Varadinova T, Matesanz AI, Marinova D, Souza P (2004) Toxicol Appl Pharmacol 197(2):107 7. Bal TR, Anand B, Yogeeswari P, Sriram D (2005) Bioorg Med Chem Lett 15(20):4451 8. Li QX, Tang HA, Li YZ, Wang M, Wang LF, Xia CG (2000) J Inorg Biochem 78(2):167 9. Khazi IM, Koti RS, Chadha MV, Mahajanshetti CS, Gadad AK (2005) Arzneimittelforschung 55(2):107 10. Walcourt A, Loyevsky M, Lovejoy DB, Gordeuk VR, Richardson DR (2004) Int J Biochem Cell Biol 36(3):401 11. Karatepe M, Karatas F (2006) Cell Biochem Funct 24(6):547 12. Kovala-Demertzi D, Demertzis MA, Filiou E, Pantazaki AA, Yadav PN, Miller JR, Zheng Y, Kyriakidis DA (2003) Biometals 16(3):411 13. Baldini M, Belicchi-Ferrari M, Bisceglie F, Dall’aglio PP, Pelosi G, Pinelli S, Tarasconi P (2004) Inorg Chem 43(22):7170 14. Capacchi S, Pelosi G, Tarasconi P (2005) J Inorg Biochem 99(7):1504 15. Coughlan ME (ed) (1980) Molybdenum and molybdenumcontaining enzymes. Pergamon Press, New York 16. Spence JT, Subrumanian P (1983) Inorg Chim Acta 79:12 17. Murray J, Macartney D, Thatcher GR (2001) Org Lett 3(23):3635 18. Iveges EZ, Leovac VM, Pavlovic G, Penavic M (1992) Polyhedron 11(13):1659 19. Szecsenyi KM, Leovac VM, Iveges EZ, Arman L, Kovacs A, Pokol G, Gal S (1997) Thermochim Acta 291(1–2):101 20. Tomic ZD, Kapor A, Miric AZ, Leovac VM, Zobel D, Zaric SD (2007) Inorg Chim Acta 360:2197 21. Mondal JU, Zamora JG, Kinon MD, Schultz FA (2000) Inorg Chim Acta 309:147 22. Vrdoljak V, Cindric M, Milic D, Matkovic-Calogovic D, Novak P, Kamenar B (2005) Polyhedron 24:1717 23. Vrdoljak V, Cindric M, Milic D, Calogovic DM, Novak P, Kamenar B (2005) Z Anorg Allg Chem 631:928 24. Cindric M, Vrdoljak V, Strukan N, Kamenar B (2005) Polyhedron 24(2):369 25. Seena EB, Prathapachra Kurup MR (2007) Polyhedron 26:3595 _ U ¨ lku¨seven B (2007) Russ 26. Kurt YD, Pozan GS, Kızılcıklı I, J Coord Chem 33(11):844 27. Altomare A, Cascarano G, Giacovazzo C, Guagliardi A, Burla M, Polidori G, Camalli M (1994) J Appl Crystallogr 27:435 28. CrystalStructure 3.5.1 Crystal Structure Analysis Package, Rigaku and Rigaku/MSC (2000–2003). 9009 New Trails Drive. The Woodlands TX 77381 USA 29. Watkin DJ, Prout CK, Carruthers JR, Betteridge PW (1996) Crystals Issue 10, Chemical Crystallography Laboratory, Oxford, UK 30. Fernelius WC, Terada K, Bryant BE (1960) Inorg Synth 6:148 31. Yamazaki C (1975) Can J Chem 53(4):610 ¨ lku¨seven B, Bal T, Sahin M (2006) Rev Inorg Chem 26(4):367 32. U 33. Chang CSJ, Enemark JH (1991) Inorg Chem 30:683 34. Enemark JH, Young CG (1993) Adv Inorg Chem 40:1 35. Valeur B (2002) Molecular fluorescence. Wiley-VCH, Germany
123
