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RESEARCH PRODUCT

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

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Two new water soluble trinuclear copper(II) complexes, [Na 6 (H 3 O) 4 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O) 3 ] 4 (ClO 4 ) 6 ·3H 2 O ( 1 ) and [K(H 2 O) 2 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O)]·3.75H 2 O ( 2 ) have been synthesized in good yield via the reaction of an unsymmetrical amino dicarboxylic ligand, N-(2-carboxybenzomethyl)-β-alanine (H 2 cbal), Cu(ClO 4 ) 2 ·6H 2 O and NaOH/K 2 CO 3 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 [Cu 3 O 4 ] core consisting of the trinuclear [{Cu(cbal)} 3 (μ 3 -OH)(H 2 O) 3 ] − and [{Cu(cbal)} 3 (μ 3 -OH)(H 2 O)] − 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.