Research Journal of Chemical Sciences _______________________________________________ ISSN 2231-606XVol. 5(5), 19-23, May (2015 Res. J. Chem. Sci. International Science Congress Association 19 Synthesis and Characterization of Antimicrobial Activities of some Transition Metal Complexes of Asymmetrical Tetradentate LigandsBorde V. L, Naglolkar B. B, Shankarwar S. G and Shankarwar A.G* Department of Chemistry, S.B.E.S. College of Science, Aurangabad, Maharashtra, INDIA Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, Maharashtra, INDIA Available online at: www.isca.in, www.isca.me Received 22nd March 2015, revised 1st May 2015, accepted 15th May 2015 AbstractThe Schiff bases have been prepared by reacting dehydroacetic acid with 6-methyl 1,3,5-triazine 2,4- diamine and 2'-hydroxy acetophenone. The Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been prepared by reacting metal nitrate with those Schiff bases in alcoholic medium. The Complexes are electrolytes in DMSO. All the complexes were characterized by elemental analysis, H -NMR, FT-IR, UV-VIS, magnetic susceptibility, conductance measurements studies. The IR spectral data suggest that the ligand behaves as a tetradentate ligand with NNNO donor atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes was found to be 1:1 (metal : ligand). X-ray diffraction and screened for their antibacterial activity against bacterium Staphylococcus aurious, B.subtilis (Gram positive) and Escherichia coli, K. pneumonae (Gram negative). The result indicated that the complexes exhibited good antibacterial activities. Keywords: Unsymmetrical schiff bases, transition metal complexes, powder X-ray diffraction, biological activity. Introduction Schiff bases are considered as a very important class of organic compounds which have wide applications in many biological aspecta. Transition metal complexes of Schiff bases are one of the most adaptable and thoroughly studied systems. These complexes have also applications in analytical, industrial, biological, clinical, biochemical, antimicrobial, anticancer, antibacterial, antifungal and antitumor activity2-5 in addition with important roles in ranging from anticorrosion, soil treatment agents and medicinal agents3,5-10.Metal complexes make the compounds effective as a stereo specific catalyst towards oxidation, reduction, hydrolysis, biological activity and other transformations of organic and inorganic chemistrySchiff base complexes play a vital role in designing metal complexes related to synthetic and natural oxygen carries. 4,11-13 However a brief survey of literature reveal that not much work has been carried out on the chelating tendency of Schiff bases derived from dehydroacetic acid, heterocyclic diamine and 2'-hydroxy acetophenone with transition metal ions. In view of the above observations it appeared worthwhile to study the synthesis, characterization and antimicrobial activity of unsymmetrical metal complexes. Material and Methods Experimental: All chemicals used were of the analytical grade (AR) Dehydroacetic acid, 6-methyl 1,3,5-triazine 2,4- diamine and 2'-hydroxy acetophenone were used for the complex preparation. IR spectra were recorded on FTIR(ATR)-BRUKER -TENSOR37 spectrometer using KBr pellets in the range of 4000-400 cm-1. H- NMR varian mercury 300MHZ spectra of ligand were measured in CDCl using TMS as internal standard. XRD were recorded on BRUKER D8 Advance. The carbon, hydrogen and nitrogen contents were determined on Elementar model vario EL-III. The UV-visible spectra of the complexes were recorded on UV-1800, SHIMADZU spectrometer. Molar conductance of complexes was measured on Elico CM 180 conductivity meter using 10-4 M solution in DMSO. Magnetic susceptibility measurements of the metal complex were done on Gouy balance at room temperature using Hg[Co(SCN)] as a calibrant. Synthesis of ligand: 6-methyl 1,3,5-triazine 2,4- diamine (0.05M) was dissolved in ethanol to which Dehydroacetic acid (0.05M) was added and mixture was refluxed for 4 hours. The yellow mono- Schiff base product formed was filtered and washed with ethanol. Mono-Schiff base thus formed was then refluxed with 2'-hydroxy acetophenone (0.05M) to prepare asymmetric ligand. Asymmetric Schiff base thus formed was cooled to room temperature and recrystalized in ethanol. Purity of the compound was checked by TLC. (Yield: 69-71%). Synthesis of metal complexes: Equimolar amount of metal and the ligands were mixed in 1:1 molar ratio using required quantities of ethanol were mixed together under constant stirring. The pH of reaction mixture was adjusted to 7-8 by adding 10% alcoholic ammonia solution and refluxed for 3 hours at room temperature on water bath. On cooling, colored solid metal complexes were precipitated out. The products were filtered, washed with warm methanol, warm ethanol, petroleum ether and Chloroform and dry at room temperature. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(5), 19-23, May (2015) Res. J. Chem. Sci. International Science Congress Association 20 NNN N H3C N C C CH O CH O CH HO OH Figure-1 Structure of ligand Results and Discussion All the metal complexes are colored solids, stable to air and soluble in polar solvents like DMF and DMSO. The physical Characteristics, analytical and molar conductance data of the ligands and metal complexes are given in tables-1 and 2. The molar conductance values of all the metal complexes in DMSO at the concentration of 10-4 M are very low indicating their non electrolytic nature. The analytical data indicate 1:1 metal: ligand stoichiometry for the Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes. 1H-NMR spectra of ligand: The H-NMR. spectra of ligand was recorded in CDCl. It shows following signals at 2.18 (s, 3H, C-CH3), 2.49 (s, 3H, C6-methyl H 6-methyl-1,3,5-triazine-2,4-diamine ), 2.50 (s, 3H, N=C-CH3), 6.28 (s, 1H, phenolic OH), 6.95 to 7.67 (m,4H, Aromatic H, H, H, Hprotons of phenyl ring). IR Spectra: The IR spectral frequencies (cm-1of ligands and their complexes are shown in table-3. The IR spectrum of the free ligands show a broad weak band 3279 cm-1 attributed to intramolecular bonding (OH). The bands 1662-1232 cm-1 are assigned to (C=N) (azomethine), (C=C) (Aromatic double bond), (C-N) (aryl azomethine) and (C-O) (enolic) stretching modes, respectively. The disappearance of IR band at 3100-3300 cm-1 (intramolecular hydrogen bonding) in the spectra of all the complexes indicates deprotonation of enolic oxygen and azomethine nitrogen in coordination to the metal ion. It is further supported by a downward shift in (C-O) in all complexes14. A downward shift in (C=N) indicates participation of azomethine nitrogen in complex formation15. The IR spectra of the metal complexes showed new bands in the 510-612 cm-1 and 469-541 cm-1 region, which can be assigned to (M-O) and (M-N) vibrations respectively16-18Table-1 Physical characterization, analytical and molar conductance data of compounds Compound Molecular formula Mol. Wt. M.P. Decomp temp. C Colour Molar Conduc. Mho Cmmol-1 L 393.40 �300 White ---- L Cr 445.39 �300 Gray 14.02 L Fe 449.24 �300 Brown 31.26 L Co 452.33 �300 Pink 21.04 L Ni 452.09 �300 Green 26.55 L Cu 456.94 �300 Blue 14.22 L Zn 458 .79 �300 White 38.07 Table-2 Elemental Analysis of Zn(II) Complex Compound Found (Calculated) C H N M L 60.90 (61.06) 4.39 (4.86) 17.67(17.80) 0 L-Zn 52.29 (52.35) 4.19 (4.17) 15.30 (15.26) 14.29 (14.25) Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(5), 19-23, May (2015) Res. J. Chem. Sci. International Science Congress Association 21 Magnetic measurements and electronic absorption spectra: The electronic spectral studies of Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex in DMSO solution. The absorption spectrum of the Cr(III)complex shows band at 37878 cm-1attributed to charge transfer transition respectively in an octahedral field19. Fe(III) complex exhibits electronic spectral band at 29411 cm-1 which can be assigned to charge transfer in an octahedral field20. The absorption spectrum of the Co(II)complex shows bands at 18248 and 38314 cm-1 attributed to 1g2g (F) and charge transfer in an octahedral field21. Ni(II) complex exhibits electronic spectral bands at 12886 and 29411 cm-1 which can be assigned to 2g2g (F) and charge transfer in an octahedral field 22. The absorption spectrum of the Cu(II) complex shows band at 39062cm-1 attributed to charge transfer respectively in an octahedral field23. Zn(II) complex exhibits electronic spectral band at 38910 cm-1 which can be assigned to charge transfer in an octahedral field24. All the Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes were diamagnetic in nature. X-ray powder diffraction: The x-ray diffractogram of metal complexes Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) of L was scanned in the range 20-80° at wavelength 1.543 Å. The diffractogram and associated data depict the 2 value for each peak, relative intensity and inter-planar spacing (d-values). The diffractogram of Cr(III) complex of L had eighteen reflections with maxima at 2 = 14.74° corresponding to d value 3.02Å. The diffractogram of Fe(III) complex of L had eighteen reflections with maxima at 2 = 14.74° corresponding to d value 3.02Å. The diffractogram of Co(II) complex of L had twenty one reflections with maxima at 2 = 14.86° corresponding to d value 3.00Å. The diffractogram of Ni(II) complex of L had sixteen reflections with maxima at 2 = 10.71° corresponding to d value 4.14Å. The diffractogram of Cu(II) complex of L had nineteen reflections with maxima at 2 = 14.84° corresponding to d value 3.00Å.The diffractogram of Zn(II) complex of L shows twenty two reflections with maxima at 2 = 10.68° corresponding to d value 4.14Å.. The X-ray diffraction pattern of these complexes with respect to major peaks of relative intensity greater than 10% has been indexed by using computer program.25 The above indexing method also yields Miller indices (hkl), unit cell parameters and unit cell volume. The unit cell of Cr(III) complex of L yielded values of lattice constants, a=10.9942 Å, b=10.0016Å, c = 14.8995 Å and unit cell volume V=1418.85Å. In concurrence with these cell parameters, the condition such as a b c and = =90 required for Monoclinic. The unit cell of Fe(III) complex of L yielded values of lattice constants, a=10.5883 Å, b=8.5768Å, c = 19.6346Å and unit cell volume V=1544.22 Å. In concurrence with these cell parameters, the condition such as a b c and = =90 required for sample to be Monoclinic. The unit cell of Co(II) complex of L yielded values of lattice constants, a=8.9162 Å, b=9.9679 Å, c = 14.5956Å and unit cell volume V=1123.41Å.In concurrence with these cell parameters, the condition such as a b c and = = 90° required for sample to be monoclinic. The unit cell of Ni(II) complex of L yielded values of lattice constants, a=8.9621 Å, b=10.5908Å, c = 16.6019Å and unit cell volume V=1364.68Å.In concurrence with these cell parameters, the condition such as a b c and = =90 required for sample to be monoclinic. The unit cell of Cu(II) complex of L yielded values of lattice constants, a=10.0120 Å, b=10.0120Å, c = 14.7903Å and unit cell volume V=1363.89Å. In concurrence with these cell parameters, the condition such as a b c and = = 90°  required for sample to be monoclinic. The unit cell of Zn(II) complex of L yielded values of lattice constants, a=8.9568Å, b=9.8841 Å, c = 16.8813Å and unit cell volume V=1294.28Å.In concurrence with these cell parameters, the condition such as a b c and = = 90° required for sample to be monoclinic were tested and found to be satisfactory. Hence it can be concluded Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex of L has monoclinic crystal system. The experimental density values of the complexes were determined by using specific gravity method26 and found to be 1.02, 1.06, 1.2, 1.04, 0.96 and 1.12 gcm-3 for Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes respectively. By using experimental density values, molecular weight of complexes, Avogadro’s number and volume of the unit cell were calculated. Number of molecules per unit cell were calculated by using equation = nM/NV and was found Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes respectively. With these values, theoretical density were computed and found to be 1.02,1.06, 1.2, 1.04, 0.96 and 1.12 gcm-3 for respective complexes. Comparison of experimental and theoretical density shows good agreement within the limits of experimental error27. Antibacterial activity: The antibacterial activities of ligand and its metal complexes were screened against bacteria such as E. Coli, B.Subtilis, S. Aurious And K.Pneumonae by paper disc plate method28. The compounds were tested at the concentration 1250ppm 2500ppm 5000ppm and 10000ppm. DMSO and compared with known antibiotics viz Tetracyclin. From Table 4and 5, it is found that the inhibition by metal chelates is higher than that of a ligand and results are in good agreement with previous findings with respect to comparative activity of free ligand and its complexes29. Table-3 Characteristic IR frequencies (cm-1) of the ligands and their complexes Compound nn (C=N) nn (C=C) nn (C-N) nn (C-O) nn (M-O) nn (M-N) L 1662 1553 1391 1232 -- -- L-Ni 1624 1537 1260 1067 612 541 L-Cu 1645 1540 1269 1071 510 469 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(5), 19-23, May (2015) Res. J. Chem. Sci. International Science Congress Association 22 Table-4 Antibacterial activity of LigandBacteriumDiameter of inhibition zone (mm) (Ligand) 1250 ppm 2500 ppm 5000 ppm 10000 ppm E. coli 07 05 06 02 S. Aurious 09 11 08 06 B.Subtilis 13 06 05 06 K.Pneumonae 09 04 07 07 Table-5 Antibacterial activity of Co(II) ComplexBacteriumDiameter of inhibition zone (mm) (Ligand-Co) Tetracyclin 1250 ppm 2500 ppm 5000 ppm 10000 ppm 1000 ppm E. coli 15 12 10 07 25 S. Aurious 19 17 13 11 29 B.Subtilis 22 16 14 12 40 K.Pneumonae 14 14 14 13 25 Figure-2 The proposed Structure of the complexes When M= Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) Conclusion Metal complexes of octahedral geometry for Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes. On the basis of the physico-chemical and spectral data discussed above, one can assume that the ligand behave as dibasic, NNNO tetradentate, co-ordinating via phenolic oxygen and imino nitrogen as illustrated in figure-2. The complexes are biologically active and show enhanced antimicrobial activities compared to free ligand. The X-ray study suggests monoclinic crystal system for Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes. References 1.Tovrog B.S., Kitko D.J. and Dragom R.S., J.Am.Chem.Soc., 98, 5144 (1976)2.Abraham K.G., Lokhande M.V. and Bhusare S., J. of Chemistry Biological and Phy. 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