Synthesis of cobalt(III)/copper(II) complexes of N,O chelators and their DFT optimization and biological evaluation

Three different metal complexes of formula [Co(nal)₂phen], 1a, [Co(bipyam)₂] 1b and [Cu(bpy)(1-Melm)(H₂O)Cl], 1c (where nal = nalidixic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanhroline, bipyam = 2,2′-dipyridylamine and 1-Melm = 1-methylimidazole) have been synthesized and structurally characterized by UV/visible, FT-IR, mass spectrometry and X-ray crystallography measurements. The tetra-coordinate of complex 1b adopts a square planar and hexa- and penta-coordinate complexes (1a & 1c) show distorted octahedral and tetrahedral geometry configurations. Density functional theory (DFT) calculations were used to optimize the molecular orbital depiction for the complexes. Utilizing a series of biophysical techniques to examine the in vitro binding studies of complexes (1a-1c) with BSA and DNA. The observed results were satisfied with strong binding interaction of complexes (1a-1c) in the subdomain IIIA of BSA as well as in the phosphate backbone of the DNA helix and follow the trend 1a > 1c > 1c. In addition, the variation in the ability of complexes to cleave BSA and DNA has also been explored by electrophoretic mobility spectrometry, which concluded that complexes have excellent cleavage ability. The computational (MD) study of the complexes (1a-1c) was attributed to the nature of ligands bound to the metal centre that influences their in vitro activities. The antibacterial study concluded that the largest inhibition zone occurred in 1a as compared to neomycin and other complexes. Further, these complexes have also revealed a significant antioxidant activity against DPPH radical. Cytotoxicity studies on three cancer cell lines (MCF-7, A-549 & HeLa) showed that complex 1a with the nal and phen ligands exhibited higher toxicity at both 24 h & 48 h, respectively.