Synthesis, crystal structure, and DNA-binding properties of a new copper (II) complex containing mixed-ligands of 2,2′-bipyridine and p-methylbenzoate

A novel copper complex of [Cu(bpy)(pba)2 · H2O] · 0.5H2O (bpy = 2,2′-bipyridine, pba = p-methylbenzoate) was synthesized. The interaction of the complex to native fish sperm DNA was investigated through electrochemistry, electronic absorption spectroscopy and viscosity experiments. In the X-ray crystallography structure, the copper (II) ion is coordinated by two oxygen atoms of two p-methylbenzoate groups, two nitrogen atoms of 2,2′-bipyridine and one water molecule. The observed changes in the physicochemical features of the copper (II) complex on binding to DNA suggested that the complex bind to DNA with intercalation mode via 2,2′-bipyridine ring into DNA base pairs. Electrochemical studies revealed that the complex prefer to bind to DNA in Cu(I) form rather than Cu(II) oxidation state form. Additionally, the nuclease activity of the title complex was assessed by gel electrophoresis assay and the results shown that the copper complex can cleave pBR322 DNA effectively in the presence of ascorbic acid.