Abstract
Transition metal complexes of Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with a tridentate ligand, 4-hydroxy-4-methyl-2-pentanone-1H-benzimidazole-2yl-hydrazone (H-HPBH) derived from the condensation of 2-hydrazinobenzimidazole and diacetone alcohol was synthesized. Characterization has been done on the basis of analytical, conductance, thermal and magnetic data, infrared,1H NMR, electronic, mass and ESR spectral data. From analytical and thermal data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand). Divalent complexes have the general formula [M(HPBH)Cl(H2O)2] in octahedral geometry, [M(HPBH)Cl] in tetrahedral and square planar stereochemistries and trivalent complexes [M(HPBH)Cl2(H2O)] in octahedral disposition. Infrared spectral data suggest that the ligand HPBH behaves as a monobasic tridentate ligand with N: N: O donor sequence towards the metal ions. On the basis of the above physicochemical data, octahedral, tetrahedral and square planar geometries were assigned for the complexes. The ligand and metal complexes were screened for their physiological activities againstE. coliandS. aureus. The order of physiological activity has been found to be Cu(II) > Ni(II) > Zn(II) > Co(II) > Cr(III) > Mn(II) > Fe (III) > ligand againstE.coliand Ni(II) > Cu(II) > Zn(II) > Mn(II) > Cr(III) > Fe(III) > Co(II) > ligand againstS. aureus.
Highlights
The coordination chemistry of nitrogen-oxygen donor ligands is an interesting area of research[1]
A great deal of attention in this area has been focused on the complexes formed by transition metal ions with hydrazones[2,3,4,5,6,7]
The metal complexes are insoluble in common organic solvents like benzene, chloroform, carbon tetrachloride, hexane, methanol, ethanol, acetone etc
Summary
The coordination chemistry of nitrogen-oxygen donor ligands is an interesting area of research[1]. The coordination chemistry and physiological activities of benzimidazole derivatives and their metal complexes are of recent interest[17,18,19,20,21,22]. The metal chelates were prepared by refluxing the methanol solutions of the respective metal chlorides (0.01 mole) and H-HPBH (0.01mole, 0.246 g) on a water bath for ca 4 h. The analytical data (Table 1) of the metal complexes show that all the metal chelates have 1:1 metal to ligand stoichiometry.
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