Nuclease activity and interaction studies of unsymmetrical binuclear Ni(II) complexes with CT-DNA and BSA.

New unsymmetrical binuclear nickel(II) complexes [Ni2L(1-5)] (ClO4)2 (1-5) were synthesized by using [NiL] [(3-((9E)-(2-((E)-(3-formyl-2-olato-5-methylbenzylideneamino)methyl) phenylimino)methyl)-3-formyl-5-methyl-2-olato)nickel(II)] with various diamines like 1,2-diaminoethane (L(1)), 1,3-diaminopropane (L(2)), 1,4-diaminobutane (L(3)), 1,2-diaminobenzene (L(4)) and 1,8-diaminonaphthalene (L(5)) and characterized by elemental analysis and spectroscopic methods. The molecular structure of binuclear nickel(II) complex 1 is determined by a single crystal X-ray diffraction method. Cyclic voltammograms of binuclear Ni(II) complexes exhibit two quasi-reversible reduction waves in the cathodic region and two oxidation waves in the anodic region. DNA binding, protein binding and DNA cleavage studies were investigated. The interactions of complexes (1-5) with calf thymus DNA were studied by spectroscopic techniques, including absorption and fluorescence methods. The binding affinities of complexes (1-5) with CT-DNA and nuclease activities are in the following order: 5> 4>3 >2>1 . Binuclear Ni(II) complex 1 cleaved the plasmid DNA by a hydrolytic pathway. The hydrolytic cleavage of DNA by the complexes is supported by evidence from free radical quenching and T4 ligase ligation. Binuclear Ni(II) complexes (1-5) displayed significant protein (bovine serum albumin) interactions. The experimental results showed that the interaction between binuclear Ni(II) complexes and BSA was mainly a static quenching process.