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

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.

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 prepared via the reaction of an unsymmetrical amino dicarboxylic ligand, N-(2-carboxybenzomethyl)-β-alanine (H2cbal), Cu(ClO4)2·6H2O and NaOH/K2CO3, and characterized. The X-ray crystal structure analyses reveal that the three copper centers are at the corners of an equilateral triangle in complex 1, whereas in complex 2, the three copper centers are at the corners of a scalene triangle. Both the two complexes are investigated for their binding affinity with CT-DNA in aqueous solution at physiological pH using a combined approach of UV–Vis and fluorescence spectroscopic techniques.Figure optionsDownload as PowerPoint slide