Synthesis, characterization, and biological activity of nickel(II) complexes with a tridentate Schiff base derived from heterocyclic aldehyde

A series of nickel(II) complexes, namely [Ni(L)(2)] (1), [Ni(L)(HL)](ClO4)(H2O) (2), [Ni(HL)(bipy)(H2O)](NO3)(ClO4)(H2O) (3), and [Ni(HL)(dien)](ClO4)(2)(H2O) (4) have been synthesized with Schiff base (L) derived from 2-pyridinecarboxaldehyde and benzoylhydrazine. The elemental analyses of the complexes indicate stoichiometry ML2 and M(L)(B), where L = N-[(1)-pyridin-2-ylmethylidene]benzohydrazide, B = diethylenetriamine/2,2'-bipyridine. L is a deprotonated as well as neutral tridentate ligand. Single-crystal X-ray structures of 1-4 reveal distorted octahedral geometry in the complexes. The molecules are connected by various hydrogen-bonding interactions. Magnetic susceptibility measurements at room temperature were 2.79-2.91 MB. The electrochemical behavior, superoxide dismutase, and antibacterial activities of these complexes were made by cyclic voltammetry, the alkaline DMSO-nitro blue tetrazolium chloride assay, and the paper disc diffusion method, respectively.