Synthesis, structure and spectroscopic studies on DNA binding, BSA interaction of a nickel(II) complex containing l–methionine Schiff base and 1,10-phenanthroline

Abstract

A new nickel(II) complex, [Ni(o-van-L-met)(phen)(CH3OH)] (o-van-L-met = Schiff base derived from o-vanillin and l-methionine, phen = 1,10–phenanthroline), has been synthesized and characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. The crystal structure shows nickel is six-coordinate in a distorted octahedral geometry. In this crystal, molecules form a 2-D plane structure via hydrogen bonds and π–π interactions. The interaction of the complex with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroism (CD), spectroscopies, and viscosity measurement. The complex binds to CT-DNA in an intercalative mode with a binding constant of (4.7 ± 0.5) × 104 M−1. The interaction of the complex with bovine serum albumin (BSA) was also studied by the multispectroscopic methods. Results illustrated that the nickel(II) complex can effectively quench the intrinsic fluorescence of BSA via a static quenching mechanism and cause conformational changes. The binding constant Kb was (6.3 ± 1.6) × 104 M−1 and the binding site number n was 0.96 ± 0.04; its bind site was located within subunit IIA of BSA.