Mixed-ligand binuclear copper(II) complex of 5-methylsalicylaldehyde and 2,2′-bipyridyl: Synthesis, crystal structure, DNA binding and nuclease activity

Abstract

A new mixed-ligand binuclear copper(II) complex [Cu(MS)(bpy)] 2.(ClO4)2, built of 5-methylsalicylaldehyde and 2,2′-bipyridyl has been synthesized and characterized by using elemental analysis, IR and UV-Vis spectroscopy. Crystal structure of the complex shows that copper(II) ion lies in a square pyramidal coordination environment. The structure consists of two symmetrical half units in which the copper(II) ion of one half unit connected with the phenolate oxygen atom of other half unit along with one perchlorate anion in the crystal lattice as free molecule. Presence of uncoordinated perchlorate anion was also confirmed by IR spectroscopy. Absorption spectroscopy exhibits d-d transition at 628 nm, which further supports the square pyramidal geometry around the copper(II) ions. EPR spectrum of the copper(II) complex at room temperature shows a broad signal without any splitting pattern at g || = 2.26,g ⊥ = 2.03 and the magnetic moment (μ eff= 1.31 BM) obtained at room temperature indicate an antiferromagnetic interaction between the two copper(II) ions through phenoxide-bridge. Binding studies reveal that the complex possesses good binding propensity (K b = 5.2 ± 1.7 × 104 M-1) and bind to nitrogenous bases of DNA through intercalation. Nuclease activity of the complex with pBR322 DNA shows that the effect of hydrolytic cleavage is dose-dependent and the oxidative cleavage indicates the involvement of hydroxyl radical and singlet-oxygen as reactive oxygen species. © 2014 Indian Academy of Sciences.