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

Abstract

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 (L¹), 1,3-diaminopropane (L²), 1,4-diaminobutane (L³), 1,2-diaminobenzene (L⁴) and 1,8-diaminonaphthalene (L⁵) 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.