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

A new coordination unimetallic and heterobimetallic complexes of hexadentate N 2 O 4 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⊥ > g e , 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.