Synthesis, structure, spectral characterization and DNA binding affinity of new water soluble trinuclear copper(II) complexes with partial cubane Cu3O4 cores

Abstract

Two new water soluble trinuclear copper(II) complexes, [Na6(H3O)4][Cu3(cbal)3(μ3-OH)(H2O)3]4(ClO4)6·3H2O (1) and [K(H2O)2][Cu3(cbal)3(μ3-OH)(H2O)]·3.75H2O (2) have been synthesized in good yield via the reaction of an unsymmetrical amino dicarboxylic ligand, N-(2-carboxybenzomethyl)-β-alanine (H2cbal), Cu(ClO4)2·6H2O and NaOH/K2CO3 in methanol at room temperature. Complexes 1 and 2 have been characterized by elemental analysis, room temperature magnetic susceptibility measurements, FTIR, UV–Vis, mass spectrometry and single crystal X-ray crystallography. Both complexes contain a partial cubane [Cu3O4] core consisting of the trinuclear [{Cu(cbal)}3(μ3-OH)(H2O)3]− and [{Cu(cbal)}3(μ3-OH)(H2O)]− unit, respectively. While the X-ray crystal structure of complex 1 reveals that the three copper(II) ions are in a distorted octahedral geometry forming an equilateral triangle, complex 2 shows that one copper(II) ion is in a distorted square pyramidal geometry, the other copper(II) ions are in a distorted trigonal bipyramidal and a distorted octahedral geometry forming a scalene triangle. Complexes 1 and 2 are investigated for their binding affinity towards CT-DNA in aqueous medium at pH∼7.5 using UV–Vis and fluorescence spectroscopic techniques. DFT calculation has been performed to calculate the Fukui functions at the metal sites as well as HOMOs and LUMOs in complexes 1 and 2 to elucidate the possible binding site with the DNA.