Mixed Ligand Complexes of Ni2+, Cu2+ and Zn2+ Ions Containing N-(4-methoxybenzylidene)isonicotinohydrazone Schiff Base and 1,10-Phenanthroline : Synthesis, Characterization, Antimicrobial and Antioxidant Properties

Abstract

N-(4-methoxybenzylidene) isonicotinohydrazone (L1) Schiff base ligand was prepared by the condensation reaction of isonicotinic acid hydrazide (INH) and 4-methoxybenzaldehyde. A series of metal complexes of Ni2+, Cu2+ and Zn2+  ions was synthesized with Schiff base ligand (primary ligand, L1) and 1, 10-phenanthroline (L2) as a secondary ligand in stoichiometry ratio (1:1:1). Moreover, the synthesized ligand and its complexes have been characterized by analytical and physical properties, conductivity, magnetic susceptibility measurements, FTIR-spectra, and UV-Visible spectra. Conductivity measurements indicated that all complexes were 1:2 electrolytic in nature. IR spectra recommended that the oxygen of the carbonyl group (=CO) and nitrogen of the azomethine group (-C=N) were coordinated with metal ions. The confirmation of a square planar structure for Ni2+ and Cu2+ complexes, as well as a tetrahedral structure for the Zn2+ ion complex, was supported by their respective magnetic moment values and UV-Visible spectra. The antimicrobial activity of the metal complexes formed by L1 and L2 was evaluated against Escherichia coli and Pseudomonas sp. The metal complexes formed by the combination of L1 and L2 were subjected to testing against Escherichia coli and Pseudomonas sp. The Zn(II) complex exhibited superior antibacterial activity compared to the reference drug Kanamycin-30 against both bacterial strains in the tested compounds. In addition, the synthesised metal complexes demonstrated a comparatively moderate level of antioxidant activity when compared to the Schiff base. The Cu2+-complex exhibited the highest level of activity, while the Zn2+ -complex demonstrated the lowest antioxidant activity, which was comparable to that of BHT.