Synthesis, characterization, DNA binding ability, in vitro cytotoxicity, electrochemical properties and theoretical studies of copper(II) carboxylate complexes

Four copper(II) carboxylate complexes, namely [Cu-2(mu-3,5-dinitrobenzoate-O,O')(4)(4-(dimethylamino)benzaldehyde)(2)] (1), [Cu-2(mu-benzoate-O,O')(4)(benzoic acid)(2)] (2), [Cu-2(mu-benzoate-O,O')(4)(H2O)(2)] [Cu(benzoate-O, O')(2)(imz)(2)](2H2O)-H-center dot (3) and [Cu(benzoate-O,O')(2)(2-Me-imz)(2)] (4) (imz = imidazole, 2-Me-imz = 2-methyl-imidazole), were synthesized and comprehensively characterized by elemental analysis, spectroscopic methods, single crystal X-ray diffraction, cyclic voltammetry (CV), topological analysis as well as theoretical studies. Single crystal X-ray diffraction revealed that products 1 and 2 are dinuclear paddle-wheel complexes, compound 3 is a co-crystal containing mononuclear and dinuclear blocks, while compound 4 is a mononuclear complex. Hirshfeld surface analysis of the compounds rationalized different types of hydrogen bonds, which also lead to the generation of H-bonded networks in 3 and 4. Their topological analysis disclosed a uninodal 4-connected 2D layer with sql topology in 3 and a uninodal 2-connected 1D chain with 2C1 topology in 4. The interaction of 1-4 with calf thymus DNA was investigated by UV-visible and fluorescence spectroscopy, revealing a moderately strong non-intercalative mode of interaction. In vitro cytotoxicity study of the complexes on HepG2 (human liver hepatocellular carcinoma) cell lines revealed a significant inhibition activity. Electrochemical study of the complexes in CH3CN (1-3) and DMSO (4) solution showed a one electron transfer corresponding to Cu(III)Cu(II)/Cu (II)Cu(II) and Cu(II)Cu(II)/Cu(I)Cu(II) redox couples. The Delta E and I-pa/I-pc values suggest that the redox couples are quasireversible. The DFT study was performed to further rationalize the crystal structures and nuclearity of the obtained copper(II) complexes.