BINUCLEAR TRANSITION METAL COMPLEXES CONTAINING 6 N MOIETIES SCHIFF BASE LIGAND: SYNTHESIS, CHARACTERIZATION AND MICROBICIDE ACTIVITIES

Complexes of Co(II), Ni(II) and Cu(II) ions with tetra amine hydrazide ligand [H4L] were prepared and characterized using physical and spectral methods. Analytical data showed that the complexes found in (1:2) ligand:metal ratio. Spectral studies revealed that the ligand bonded to the metal ion in neutral tetradentate or tetrabasic tetradentate manner through azomethine nitrogen atom, protonated/deprotonated hydroxyl group. From the electronic spectral data together with magnetic susceptibility values a distorted octahedral structure can be proposed for all complexes except complex 2 which has square planar structure. Electron spin resonance spectra for Co(II) complex 6 revealed axial symmetry with g|| > g perpendicular to > ge, indicating distorted octahedral or square planar structures and the unpaired electron exists in a d(x2-y2) orbital with marked covalent bond feature. Quantum chemical calculations have been performed to study structures and energetics of the ligand and its complexes. The prepared complexes showed good to excellent antimicrobial activity, and the most active complexes against Aspergillus niger were 3 with zone of inhibition of 23 mm. Complex 7 showed interesting activity against Escherichia coli with zone of inhibition of 23 mm.