Synthesis, characterization, electrochemical studies, DNA binding, and cleavage activity of mixed copper(II)oxime DMSO complexes

Mixed ligand complexes having molecular formulae Cu(L)2(DMSO)2 [where L ¼ salicylaldoxime (SAO), 2-hydroxyacetophenone oxime (HAO), and resacetophenone oxime (RPO)] have been synthesized and characterized by molar conductivity, magnetic susceptibility, UV–vis, IR, and ESR methods. The electronic and ESR spectra suggest distorted octahedral geometry for mixed ligand complexes. From ESR data all the complexes follow the order gjj 4g? 4 2.0037 showing covalent bonding nature and copper(II) (d 9 ) ion in axial symmetry with unpaired electron in dx27y2 orbital. Cyclic voltammetric studies show quasireversible reduction attributable to Cu 2þ /Cu þ . Absorption titration studies revealed that each complex is an avid binder of CT DNA. The apparent binding constants are in the range 3.2 6 10 5 to 2.4 6 10 6 . The cleavage activity of complexes was carried out on double-stranded pBR322 circular plasmid DNA using gel electrophoresis. All complexes show increased nuclease activity in the presence of oxidant (H2O2) and cleavage is strongly dependent on time of incubation and concentration of complex. Control cleavage experiment carried out in the presence of potential inhibitors, viz. dimethyl sulfoxide, tert-Butyl alcohol, ethylenediaminetetraacetic acid and NaN3, inhibits cleavage activity suggesting an oxidative mechanism with major active species involving . OH in cleavage of plasmid DNA.