Syntheses and structures of tetracopper(ii) complexes with an N-benzoate-N′-[3-(2-hydroxylethylammino)propyl]oxamide ligand: reactivity towards DNA, cytotoxic and antimicrobial activities

Abstract

Two new tetracopper(II) complexes with formulae of [Cu4(bhpox)2(dabt)2](ClO4)2 (1) and [Cu4(bhpox)2(dmbt)2](ClO4)2·2H2O (2), where H3bhpox stands for N-benzoate-N′-[3-(2-hydroxyl-ethylammino)propyl]oxamide, dabt and dmbt are 2,2′-diamino-4,4′-bithiazole and 2,2′-dimethyl-4,4′-bithiazole, respectively, have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectral studies and single-crystal X-ray diffraction. The crystal structures reveal that both of the tetracopper(II) complexes are assembled by a pair of oxamido-bridged bicopper(II) units through carboxyl bridges, but the configuration of the μ-oxamido-bridge is cis- in complex 1 while trans- in complex 2. All the copper(II) ions in the two tetranuclear complexes are located in a square-pyramidal environment. Through hydrogen bonds, the two tetracopper(II) complexes 1 and 2 are assembled into a three-dimensional supramolecular structure and a two-dimensional network structure, respectively. The reactivity towards DNA, cytotoxic and antibacterial studies show that both the tetracopper(II) complexes can bind to HS-DNA in the mode of intercalation, and the cytotoxic and antibacterial activities are consistent with their DNA-binding abilities, following the order of 1 < 2. The influence of the substituents on terminal ligands in the two tetracopper(II) complexes on the structure, reactivity towards DNA, cytotoxic and antibacterial activities is preliminarily discussed.