Synthesis, crystal structure description, electrochemical, and DNA-binding studies of “paddlewheel” copper(II) carboxylate

Abstract

Dimeric paddlewheel copper(II) complex, pyCu(phenylacetate)4Cupy, where py = pyridine, has been prepared and the crystal structure determined. Single crystal X-ray diffraction (XRD) revealed three crystallographically independent molecules in the unit cell. The geometry around each Cu(II) is square pyramidal with monodentate pyridine at the apical and bidentate carboxylates in the equatorial positions. The supramolecular structure of the complex arises primarily as a result of C–H • • •O along with some contribution of C–H• • •C interactions, resulting in the preferential alignment of the molecules along the c-axis. The purity of the crystalline complex has been confirmed through powder XRD study. Electrochemical solution study of the complex in aqueous DMSO (1 : 4) showed two redox couples corresponding to Cu(III)/Cu(II) and Cu(II)/Cu(I) irreversible electron transfer. The values of various voltammetric variables, such as diffusion coefficient (Do), heterogeneous rate constant (k°), formal potential (E°), and charge transfer coefficient (α), have been calculated before and after DNA addition. DNA binding of the complex has been explored through cyclic voltammetry, UV–visible spectrophotometry, and viscosity measurement which have exhibited a mixed electrostatic and intercalative mode of interaction. Cyclic voltammetry indicated self-induced redox activation and potential anticancer ability of the complex, supported by UV–visible spectrophotometry as well as viscometry.