Transition metal complexes of a hydrazone-oxime ligand containing the isonicotinoyl moiety: Synthesis, characterization and microbicide activities

Complexes of VO2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Ru3+ and UO22+ with (3-(hydroxyimino)butan-2-ylidene)isonicotinohydrazide were synthesized and characterized using physical and spectral methods. Analytical data revealed that the complexes formed in 1:1 or 1:2 metal-ligand ratios. Spectral studies showed that the ligand bonded to the metal ion in neutral tridentate, monobasic tridentate or monobasic bidentate fashion through azomethine nitrogen atom, protonated/deprotonated imine oxime group and/or ketonic/enolic carbonyl group. From the electronic spectral data together with magnetic susceptibility values a square planar, tetrahedral or distorted octahedral structure can be proposed for all complexes. Electron spin resonance spectra for Cu2+ complexes (2-4) revealed axial symmetry with g(||) > g(perpendicular to) > g(e), indicating distorted octahedral or square planar structures and the unpaired electron exists in a d open="(" close=")">x2-y2 orbital with marked covalent bond feature. The prepared complexes showed good to excellent biological activity, and the most active complexes against Aspergillus niger were 4 and 9 with zone of inhibition of 25 and 23mm, respectively. Complexes 10 and 11 showed interesting activity against Escherichia coli with zone of inhibition of 44 and 32mm, respectively.