Synthesis, physicochemical studies and biological evaluation of unimetallic and heterobimetallic complexes of hexadentate dihydrazone ligands

A new coordination unimetallic and heterobimetallic complexes of hexadentate N2O4 donor dihydrazone ligands were prepared by the condensation of 4-formyl antipyrine with adipic dihydrazide and succinic dihydrazide. The ligands (1) and (11) and their complexes thoroughly characterized using various analytical, physical and spectroscopic techniques, which indicate a distorted octahedral geometry around the metal ions. The ESR spectra of solid copper(II) complexes (2-4) and (12-14) showed axial symmetry with g||>g⊥ > ge, indicating distorted octahedral structure and the presence of the unpaired electron in a d(x2−y2) orbital with significant covalent bond character. The antimicrobial activity results of the metal compounds (2-5), (7), (10), (12-15) and (17) show that, all these complexes exhibit inhibitory moderate to mild effects towards Bacillus subtilis, Escherichia coli and Aspergillus niger.