O-bridged and paddlewheel copper(II) carboxylates as potent DNA intercalator: Synthesis, physicochemical characterization, electrochemical and DNA binding studies as well as POM analyses

Abstract

Dinuclear copper(II) complexes ACu(B)4CuA (1 and 2), where A is N-donor ligand such as 2,2′-bipyridine (1) and 3-bromopyridine (2) and B is O-donor carboxylate ligand such as 4-methylphenyl acetate, have been synthesized and characterized by FT-IR and single crystal X-ray crystallography. Crystallographic data of complex 1 revealed a square pyramidal geometry for each Cu center with bridging oxygen atoms at the elongated axial sites. For complex 2 a paddlewheel structure with bidentate coordination mode of the carboxylate moieties was observed. The mode of coordination of the carboxylate moiety was also determined from FT-IR data indicating a monodentate coordination mode in complex 1 and a bridging bidentate mode in complex 2. A close agreement for Δν value was also observed between the FT-IR and single crystal X-ray data for both the complexes. Electrochemical studies of the complexes showed two redox peaks corresponding to Cu(III)/Cu(II) and Cu(II)/Cu(I) processes. The values of diffusion coefficient (Do), heterogeneous rate constant (k°), formal potential (E°) and charge transfer coefficient (α) have been calculated for the electron transfer processes and correlated to the structural parameters of the complexes. The complexes bind to DNA via intercalative interactions resulting in significant hypochromism and bathochromic shift as confirmed by UV–Vis spectroscopy. The synthesized complexes have a negative value of miLogP (−0.97 for complex 1 and −4.22 for complex 2) evaluated by Petra/Osiris/Molinspiration (POM) analyses which indicate their ability to penetrate through bio-membranes.