A chiral binuclear nickel(II) complex with Schiff base ligand: synthesis, crystal structure, DNA/BSA binding interactions and SOD activity

A chiral binuclear Ni(II) complex [Ni2(o-van-ala)2(phen)2] (o-van-ala = a Schiff base derived from o-vanillin and l-alanine, phen = 1,10-phenanthroline) has been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction result showed that the Ni(II) complex contains two nickel centers, which are further bridged and coordinated by two o-van-ala Schiff base and two phen ligands in a cis-conformation. Each nickel atom is six-coordinated in a distorted NiN3O3 octahedral geometry. The interaction of the Ni(II) complex with calf thymus DNA (CT-DNA) has been investigated by spectroscopic methods. Based on results obtained, an intercalative binding mode has been proposed. In addition, the interaction between the Ni(II) complex and bovine serum albumin (BSA) has also been studied by various spectroscopic techniques. Results indicated that the Ni(II) complex can quench the intrinsic fluorescence of BSA in a static quenching process. The binding constant (Kb) and the number of binding sites (n) were calculated to be 2.92 × 106 M−1 and 1.21, respectively. Site-selective competitive binding experiment indicated that the binding site of the Ni(II) complex locates in site I in sub-domains IIA of BSA. The Ni(II) complex also displayed a significant superoxide anion scavenging activity.