Synthesis, structure characterization, DNA binding, and cleavage properties of mononuclear and tetranuclear cluster of copper(II) complexes

Abstract

Two copper(II) complexes, cluster 1, and mononuclear 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio for 1 and 1:2 ratio for 2) with CuCl2 in a methanol solution. In 2, which is a new complex, the ligand acts as a tetradentate which binds the metal ion via two amide-O atoms and two imine-N atoms providing an N2O2 squa-re-planar around the copper(II) ion. The absorption spectra data evidence strongly suggested that the two copper(II) compounds could interact with CT-DNA (intrinsic binding constant, Kb = 0.45 × 10⁴ M⁻¹ for 1 and Kb = 2.39 × 10⁴ M⁻¹ for 2). The super coiled plasmid pBR322 DNA cleavage ability was studied with 1 and 2 in the presence and absence of H₂O₂ as an oxidant. In both the absence and the presence of an oxidizing agent, complex 2 exhibited no nuclease activity. However, even in the absence of an oxidant, complex 1 exhibited significant DNA cleavage activity.