Synthesis, Characterization and antimicrobial Activity ...

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Ahmed A. A., BenGuzzi S. A. and EL-. Hadi A. A., J of Sci. and Its Appli., 1(1), ... Farooque M. A., Mosaddik M. A., Islam. M. S., Alam M. S. and Bodruddoza M.
Ultra Chemistry Vol. 6(2), 211-220 (2010).

Synthesis, Characterization and antimicrobial Activity of Ternary Cr(VI) and Fe(III) Metal Complexes of 2-{[(2-aminophenyl)imino] methyl} phenol and Metformin SANGITA SHARMA,a* JAYESH RAMANI,a DIPIKA DALWADI,a JASMIN BHALODIA,a DHARA PATELa and RAJESH PATELb a

Department of chemistry, Hemchandracharya North Gujarat University, Patan, Gujarat-384 265 (INDIA) b Department of Life Science, Hemchandracharya North Gujarat University, Patan, Gujarat-384 265 (INDIA) *Corresponding author: E-mail: [email protected] (Acceptance Date 27th August, 2010)

Abstract Schiff base 2-{[(2-aminophenyl)imino] methyl} phenol was synthesized from O-phynelendiamine and salicyldehyde. Metal Complexes of Cr(VI) and Fe(III) were synthesized from Schiff base and metformin. The synthesized transition metal complexes were characterized by elemental analyses, conductance and magnetic susceptibility measurements, as well as spectroscopic (IR, electronic) and thermal studies. IR spectral studies revealed the existence of the ligands in the amine form in the solid state. The magnetic and electronic spectral studies suggest an octahedral geometry for all the complexes. The metformin acts as a bidentate ligand and Schiff base of O-phynelendiamine and salicyldehyde acts as a tridentate ligand. Antimicrobial screening of the Schiff base, ligand and transition metal complexes were determined against the bacteria Escherichia coli and Bacillus megaterium. Key word: Schiff base, metal complexes, Antimicrobial activity, metformin, ligand

Introduction

M etformin

hydrochloride (N,NDimethyl-imido-dicarbonimidic diamide hydrochloride) is a strongly basic bisusbstituted

guanidine derivative with short side chains1. The metabolic abnormalities of non-insulindependent diabetes mellitus (NIDDM) are generally acknowledged to result from a combination of insulin resistance and impaired

212 insulin secretion2. Schiff bases offer a versatile and flexible series of ligands capable to bind with various metal ions to give complexes with suitable properties for theoretical and/or practical applications3. The chemistry of metal complexes containing salen-type Schiff-base ligands derived from condensation of aldehydes and amines is of enduring significance, since they have common features with metalloporphyrins with respect to their electronic structures and catalytic activities that mimic enzymatic hydrocarbon oxidation4. Catalytic activity of such metal complexes has been highlighted in the past few decades5. The presence of transition metals in human blood plasma indicates their importance in the mechanism for accumulation, storage and transport of transition metals in living organisms6-8. Experimental Materials The ligands O-phenylenediamine, salicyldehyde, metformin and transition metal salts were obtained from S. d. fine chemicals Ltd. India and Escherichia coli; MTCC 1687, Bacillus megaterium; MTCC 428 were collected from MTCC Bangalore, India. Preparation of Schiff base and Metal complexes : The Schiff base under investigation was prepared by mixing an ethanolic solution (50 cm3) of (1.22 gm) 0.01 mole of Salicylaldehyde with (1.08 gm) 0.01 mole of o-phenylenediamine in the same volume of ethanol. Few drops of 10% NaOH were added to adjust pH-7 and the obtained mixture then refluxed with stirring for two hours. The

Sangita Sharma, et al. obtained precipitate was collected by filtration through Buchhner funnel, recrystallized from ethanol and dried at room temperature. The yield was 65% and its melting point obtained was 195ºC The complexes under investigation were prepared by three mixing 50 cm 3 ethanolic solution of 0.01M Schiff base, 0.01M metal salt and 0.01M metformin. If the complexes did not separate, few drops of ammonium hydroxide were added to adjust the pH-8. The obtained mixture was refluxed with continues stirring for four hours. The resulted mixture was filtered, product was collected and then washed several times with hot ethanol until the filtrate became clear. The complexes were dried in desiccator over anhydrous CaCl2 under vacuum. The yield ranged from 60-75% and the melting points of all complexes was above 350ºC. Analysis and Physical Measurements : Elements like C, H, O and N were analyzed with a Perkin-Elmer 2400 series II elemental analyzer. The metal content was estimated with titrematry method using standardized EDTA solution after decomposing the complexes with aquaregia mixture. Magnetic susceptibilities were measured at room temperature on a Gouy9 balance using Hg[Co(CNS)]4 as calibrate. The IR spectra were recorded on a Perkin-Elmer Lamda-983 spectrometer with samples prepared as KBr pellets and UVVisible reflectance spectra were obtained on a Beckman DK-2A spectrophotometer using MgO as reference. Thermal measurements were carried out using perkin-Elmer TGA7DSC-PYRIS-1-DTA-7 thermal analyzer

Synthesis, Characterization and---phenol and Metformin.

213

maintained at a 10oC min-1 heating rate.

Conductance Measurements :

Antimicrobial Assay :

The conductivity of complexes was measured in 1:1 mixture of methanol and water at room temperature. All the complexes showed the molar conductance values for 10 -3 M concentration in range 8 to 14 ohm-1cm2 mol-1. It is suggesting that all complexes have non electrolyte nature10. The molar conductance values of the complexes are listed in table 1.

The experiments were designed so as to test the effect of the presence of the ligand and their metal chelates in liquid culture media. 210-3M of ligands and their metal chelates Cr(VI) and Fe(III) were supplemented in nutrient broth. The flasks were inoculated with 5% (v/v) actively growing inoculums and incubated for 24 hours on rotary shaker adjusted at 120 rpm and 37oC. After the incubation growth was measured spectrophotometrically at 660 nm. The % growth inhibition was calculated with reference to growth in the respective medium without any inhibitory compounds. Results and Discussion The analytical data of the complexes is presented in Table 1 indicates 1:1:1 stoichiometry. The general equation for the formation of the complexes is shown as below: Mx+ + HA + L

MAL + XH+

Where Mx+ = Cr(VI) or Fe(III) A = Schiff base and L = Metformin All synthesized complexes were colored and possess high decomposition points. All were amorphous and stable in air. The complexes were partially soluble in methanol and insoluble in water and other organic solvents like benzene, chloroform, carbon tetrachloride. Hence it was not possible to characterize them by conventional methods like osmometry or viscosity measurements.

Infrared Spectra : There is strong coupling among the IR bands of ternary complexes and hence quantitative interpretation of the bands in the IR spectra is not possible without normal coordinate analysis. Important IR frequencies of the complexes are listed in Table 2 along with their suggested assignments. The IR spectra of all of the complexes differed from those of the ligands. A strong band ascribed to the presence of υOH of schiff base appears at 3090 cm-1 in spectrum. This band disappeared in spectra of all metal complexes which accounts for coordination of -OH. Similarly frequency appear at 3200 cm-1 to 3460 cm-1 in complexes, which gives indication for presence of water molecules. The spectra of schiff base showed υC=N- stretching band, thus band was observed at 1660 cm-1 related to schiff base but such band does not appear in the spectrum of metformin. The same band in IR spectra of complexes is displaced to 1652cm-1 for Cr(VI) and 1539cm-1 for Fe(III). There was shift of 8-38cm-1 for various heterochelates formed indicating for involvement of this frequency in coordination11. The -NH2

Cr C17H38N7O12 Fe C17H32N7O6 2Cl Brown Dark brown

Colour

557.26

601.41

Formula Weight

υ-NH

1528 Sh.(s) 1539 Sh.(s)

Schiff Base [CrO3·A·L·H2O] 7H2O [Fe·A·L·H2O] 4H2O·2Cl

C

H

O

3050 Sh.(m)

3120 Sh.(m)

-

3367 Sh.(s)

Metformin

1362 Sh.(m)

1368 Sh.(m)

-

1381 Sh.(m)

Metformin

1642 Sh.(s)

3460 (m)

3210 (m)

3090 Sh.(m)

1660 Sh.(s) 1652 Sh.(s)

-

A/complexes

-

A

1612 sh.(s) 910 sh.(m) 1604 sh.(s) 835 sh.(m) 1604 sh.(s) 841sh.(m)

-

A.

1260 Sh.(m)

1259 Sh.(m)

1361 Sh.(m)

-

A.

υ M-N=C

-

-

Cl

574 807 Sh.(m) sh.(m)

464 Sh.(m)

479 Sh.(m)

-

-

>350

>400

D.P. (oC)

848 Sh.(m)

855 Sh.(m)

-

-

υ M-OH2

59.9

2.40

Molar Cond. ohm-1 cm2 mol-1

υ M-0

12.52 (12.64)

624 783 Sh.(m) sh.(m)

-

-

N 16.75 (16.79) 17.51 (17.43)

υ M-N

8.88 34.98 6.41 32.81 (8.90) (34.86) (6.51) (32.88) 9.41 36.39 6.46 16.97 (9.94) (36.31) (6.51) (17.10)

M

Analysis of elements (%) Found (Calculated)

A = Schiff Base, L = Metformin, (s) = Strong, (m) = Medium, Sh. = sharp

1580 Sh.(s)

Metformin

Metformin

Complex

70 (8.77) 69 (8.91)

Yield % (g)

Table 2. Infrared spectral data of the metal complexes (cm-1) υ-C=NH υ-N-CH3 υ-C=N- υ –OH υ-C=Cυ-NH

A = Schiff Base, D.P. = Decomposition point, L = Metformin

[CrO3·A·L·H2O] 7H2O [Fe·A·L·H2O] 4H2O· Cl3

Complex

Molecular Formula

Table 1. Analytical data and some physical properties of the metal complexes

214 Sangita Sharma, et al.

Synthesis, Characterization and---phenol and Metformin. stretching appears in Schiff base at ~1340 which is reported by sharp and medium stretching band. The band similar in behavior to –NH2 stretching of Schiff base studied complexes was observed in all heterochelates, but it has shifted to ~1263cm-1 for Cr(VI) and ~1260cm-1 for Fe(III) respectively. This shift again accounts for coordination of –NH2 group of Schiff base with metal ions. Two more bands which were strong and of medium intensity were found in range of 624-590 and 783-800cm-1 in studied heterochelates, these can be arranged as M-N and M-N=C stretchings respectively12. A sharp and strong band obtained at ~480cm-1 in heterochelates can be attributed to M-O stretching13.

215

Thermo gravimetric Analysis : Thermogravimetric analysis of the metal complexes was carried out in air by heating at a constant rate of 10oC per minute using a Perkin-Elmer TGA-7DSC-PYRIS-1 DTA-7 thermal analysis system. The complexes lost weight gradually during every phase of the experiment, then the samples underwent an accelerated weight loss and finally in the temperature range of about 500-600oC rate of weight loss became much more moderate. During the initial phase the gradual weight loss may be due to water of hydration which may be either crystal or coordinated water.

Table 3. Cumulative % weight loss data of metal complexes at various temperatures from thermogram Complex % Weight loss at temperature (oC) 50 100 150 200 250 300 350 400 450 500 550 Metformin 0.1 0.1 0.1 1.2 12.1 42.0 71.2 80.0 82.0 86.5 88.0 Schiff Base 0.1 0.1 1.5 1.8 8.0 31.5 56.5 70.0 74.2 77.5 79.9 [CrO3·A·L·H2O] 1.2 2.5 3.5 4.9 7.5 11.5 14.2 15.5 17.0 19.9 23.1 7H2O [Fe·A·L·H2O] 1.5 2.5 3.3 7.2 10.2 12.8 15.0 22.5 25.0 27.5 30.0 4H2O·2Cl A = Schiff Base L = Metformin

(OC)

600 90.0 80.0 25.0 32.5

Table 4. Cumulative weight loss data of metal complexes at 50OC to 250OC Complex Found 50oC 100oC 150oC 200oC 250oC gm % gm % gm % gm % gm % [CrO3·A·L·H2O] 7.02 1.2 14.63 2.5 20.48 3.5 28.67 4.9 43.89 7.5 7H2O [Fe·A·L·H2O] 8.90 1.5 14.84 2.5 19.58 3.3 42.73 7.2 60.55 10.2 4H2O·2Cl A = Schiff Base, L = Metformin

216

Sangita Sharma, et al.

Thermogravimetric data and cumulative weight losses of metal complexes at 150oC and 200oC are presented in table 3 and 4 respectively. The rate of decomposition of metal complexes was lower than that of the ligand suggested that there may be weak intermolecular hydrogen bonding. The percentage of loss observed in all complexes above 300oC was higher, it indicated for decomposition of complexes and formation of oxides.

of these complexes were also obtained from their electronic data and magnetic moments which are presented in tables 5 and 6. The Fe(III) complexes was found to be paramagnetic, as expected for six-coordinated d5 octahedral complexes. The electronic spectra of Fe(III) d5 complex exhibits electronic transition at 4347 cm-1(υ1), 6756 cm-1(υ2), 12345 cm-1(υ3) and gives B = 605 cm-1, β = 0.59 and β0 = 41%. These transitions were assigned to 4A1  4E , 6A1  4T1, 6A1  4T2 for Fe(III) complexes in octahedral environment due to large crystal field splitting.

Electronic Spectra and Magnetic Measurements : The information regarding geometry

Table 5. Electronic spectra and magnetic moment data for the complexes Complex Absorption region Band assignment Magnetic (cm-1)

moment

Geometry

µeff (B.M.) 5128 cm-1 CrO3·A·L·H2O] 7H2O

1

T1 

1

E

-1

1

T2 

1

-1

1

T2 

1

4347 cm-1

4

A1 

4

-1

6

A1 

4

6

4

14285 cm

34129 cm broad



A2

Octahedral

E

band [Fe·A·L·H2O] 4H2O·2Cl

6756 cm

-1

12345 cm

Table 6. Parameters of the d-d transition Complex (cm-1) υ2 υ3 [CrO3·A·L·H2O] 7H2O [Fe·A·L·H2O] 6756 12345 4H2O·2Cl

A1 

E

T1

1.73

Octahedral

T2

electronic spectra of metal complexes Dq B -1 (cm ) (cm-1) β= B/Bo υ4

β o (%)

-

-

-

-

-

-

4347

605

0.59

41

Synthesis, Characterization and---phenol and Metformin.

217

Table 7. Effect of ligand and metal complexes on the growth of bacteria Bacteria Compound

Escherichia coli Inhibition

Bacillus megaterium Inhibition

in (mm)

in (mm)

Schiff Base

7.14

8.01

Metformin

10.41

10.07

[CrO3·A·L·H2O] 7H2O

12.72

14.11

[Fe·A·L·H2O] 4H2O·2Cl

10.32

7.43

H N

NH2

O Fe HN

2+

4H 2 O.2Cl

O H2 NH CH3

H 2N

N H

N CH3

Figure 1. Octahedral geometry for Fe(III) complex

-

218

Sangita Sharma, et al.

H N

O

O O Cr HN

O

NH 2

-

OH 2 NH CH 3

H 2N

N

N

H

CH 3

Figure 2. Octahedral geometry for Cr(VI) complex

The lowest long wavelength will be T 1 2e LMCT ( 1 T 2  1 A 1). The other expected configuration are (t1)T e1 which gives four states 3T1, 3T2, 3T1 and 1T2 but these are shortly spaced and cannot be resolved. In our studies, the electronic spectrum of Cr(VI) complex exhibits electronic transitions at 5128 cm-1, 14285cm-1 and 34,129cm-1. 1

The antimicrobial effects of metal complexes at 210-3 M concentration on the

growth of bacteria (Escherichia coli and Bacillus megaterium) Growth inhibition pattern for free ligands, uncompleted metal salts and synthesized metal complexes are given in Table 7. The highest activity was reported with Cr(VI) complexes with 12.7 mm and 14.11 mm growth inhibition for E. coli and B. megaterium respectively. The least activity has been reported for the Fe(III) complexes.

Synthesis, Characterization and---phenol and Metformin. All synthesized metal complexes have shown more inhibitory activity against bacteria as compared to parental ligands. Similar correlation and increase in antibacterial activity of ligands on Complexation with reference to parent ligands has been well cited14-17. Such increased activity of the metal chelates can be explained on the basis of Overtone’s concept and chelation theory. According to Overtone’s concept of cell permeability the lipid membrane that surrounds the cell favors the passage of only lipid soluble materials due to which liposolubility is an important factor that controls antimicrobial activity. On chelation, the polarity of metal ion was reduced to a greater extent due to the overlap of the ligand orbital and partial sharing of the positive charge of the metal ion with donor groups. Further, it increases the delocalization of π-electrons over the whole chelates ring and enhances the lipophilicities of the complex. The increased lipophilicities of complexes permit easy penetration into lipid membranes of organisms and facilitates as blockage of metal binding sites in enzymes18. Conclusion On the basis of elemental analyses, IR, thermogravimetric analyses, uv-visible reflectance spectra, molar conductance and magnetic properties, it is possible to assign octahedral geometry to the all metal complexes as shown in Fig. 1 and Fig. 2. The calculated values of β are favorable for assigned structure an accounted for covalent character of complexes. We are optimistic that future studies on biological properties of these complexes of Schiff base, metformin and there derivatives may lead to the development of a new class of

219

specific and effective pharmaceutical agents. Cr(VI) complexes have shown promising antibacterial activity against E. coli and B. megaterium. Least activity is shown for Fe(III) complexes because Fe(III) act as cofactor in many systems. The antimicrobial activity was explored on the basis of overtone concept of cell permeability. References 1. Stepensky D., Friedman M., Srour W., Raz, I. and Hoffman A., J. Control. Rel., 71, 107 (2001). 2. Stumvoll M., Nurjahan N., Perriello G., Dailey. G and Gerich J. E., N Engl J Med., 33(9), 550 (1995). 3. Ahmed A. A., BenGuzzi S. A. and ELHadi A. A., J of Sci. and Its Appli., 1(1), 79, (2007). 4. Groves J. T., in: P. Ortiz de Montellano (Ed.); Cytochrome P-450: Structure, Mechanism and Biochemistry; Plenum Press: New York, Vol. 7, 1 (1986). 5. Chatterjee D. and Mitra A., J. Coord. Chem., 57(3), 175 (2004). 6. Sullivan J. F., J. Nutr., 109(8), 143 (1979). 7. McNeely M. D. Clinical. Chem., 17, 1123 (1971). 8. Prasad M. D., Trace Element and Iron in Human Metabolism; Plenum Medical Book Company: Londan (UK), (1978). 9. Pierce W. S., Magneto Chemistry, New York (USA): Interscience, 62 (1956). 10. Morrison and Boyd, Organic Chemistry, 6th ed., Prentic Hall Pvt. Ltd., 746 (1997). 11. Patel A. K., Patel V. M. and Joshi J. D.,

220 Synth. React. Inorg. Met.-Org. Chem., 29(2), 193 (1999). 12. Nakamoto K., Infrared and Raman Spectra of Inorganic and Coordination Compounds, 4th ed., New York (USA): John Wiley Sons, 208 (1993). 13. Joshi J. D., Sharma S., Patel G. and Vora J. J., Synth. React. Inorg. Met.-Org. Chem., 32(10), 1729 (2002). 14. Konstantinovic S. S., Radovanovic B. C., Cakic Z. and Vasic V., J. Serb. Chem. Soc., 68(8-9), 641 (2003).

Ultra Chemistry Vol.6(2), (2010). 15. Farooque M. A., Mosaddik M. A., Islam M. S., Alam M. S. and Bodruddoza M. A.K., Online J. Bio. Sci., 2(12), 797 (2002). 16. Patel K. M., Patel K. N., Patel N. H. and Patel M. N., Synth. React. Inorg. Met.-Org. Chem., 31(2), 239 (2001). 17. Mishra A. P. and Soni M., Met Based Drugs, Hindawi Publishing Corporation, (2008). 18. Gudasi B. K., Shenoy R.V., Vadavi R. S., Patil M. S. and Patil S. A., Chem. Pharm. Bull., 53(9), 1077 (2005).