Metal-Based Molecular Design Tuning Biochemical Behavior: Synthesis,Characterization, and Biochemical Studies of Mixed Ligand Complexes Derived From 4-Aminoantipyrine Derivatives

Biosensitive mixed ligand complexes of metals (Fe(III), Co(II), Ni(II), Cu(II), and Zn(II)) with the Schiff bases of L¹ and HL² (L¹: obtained through the condensation of 4-aminoantipyrine with furfuraldehyde; HL²: derived from 2-aminophenol and 3-nitrobenzaldehyde) were synthesized. They were characterized using elemental analysis, magnetic susceptibility, molar conductance, proton nuclear magnetic resonance spectroscopy, ultraviolet–visible spectroscopy, infrared, and electron spin resonance techniques. Cyclic voltammogram of the complexes in dimethylsulfoxide solution at 300 K was recorded and their salient features were summarized. The X-band electron spin resonance spectrum of the copper complex in dimethylsulfoxide solution at 300 and 77 K was recorded. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, and Pseudomonas aeruginosa and the fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola, and Candida albicans by disc diffusion method. Comparative study of inhibition values of the Schiff bases and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. DNA binding studies of metal complexes using ultra-violet-visible spectroscopy and cyclic voltammetry paved the way to probe their DNA binding abilities. The solvatochromism and superoxide dismutase activity of these complexes have also been examined.