DNA Binding and Cleavage Activity of cis‐Cobalt Aromatic Oxime Complexes and Its Pyridine/imidazole Adducts

cis‐Cobalt complexes with salicycaldoxime(SAO), (Z)‐1‐(2‐hydroxyphenyl)ethanonoxime (HEO), (Z)‐1‐(2,5‐dihydroxyphenyl)ethanonoxime (DEO), (Z)‐1‐(2,5‐dihydroxyphenyl)(phenyl)methanonoxime (DPO) and their adducts with pyridine (Py) and imidazole (Im) were synthesized and characterized by elemental analysis, magnetic susceptibility, UV‐Vis and IR spectra. The electrochemical studies were carried by cyclic voltammeter, the peak potential separation and formal potential of complexes were independent of sweep rate or scan rate (ν) indicating a quasi reversible one‐electron redox process. Absorption studies and thermal denature studies revealed that each of these octahedral complexes is an avid binder of calf thymus DNA. The apparent binding constants for mixed ligand complexes are in order of ～10³‐10³ M^?1. Based on the data obtained in the DNA binding studies a partial intercalative mode of binding is suggested for these complexes. The nucleolytic cleavage activity of parent complexes and their pyridine adduct were carried out on double stranded pBR322 circular plasmid DNA by using a gel electrophoresis experiment in the presence and absence of oxidant (H₂O₂). All the metal complexes show enhanced cleavage activity in presence of oxidant. The hydrolytic cleavage of DNA of Co(DEO)₂ and Co(DPO)₂ is evidenced from the control experiments showing discernable cleavage inhibition in the presence of the hydroxyl radical inhibitor DMSO and EDTA.