Antibacterial Activities and Nuclease Properties of Two New Ternary Copper(II) Complexes with 2-(4′-Thiazolyl)-benzimidazole and 2,2′-Bipyridine/1,10-phenanthroline

Two new complexes: [Cu(TBZ)(bipy)Cl]Cl center dot H2O (1) and [Cu(TBZ)(phen)Cl]Cl center dot H2O (2) [TBZ=2-(4'-thiazolyl)benzimidazole, phen=1,10-phenanthroline and bipy=2,2'-bipyridine] have been synthesized and characterized by elemental analysis, molar conductivity, IR, and UV-vis methods. Complex 2, structurally characterized by single-crystal X-ray crystallography, crystallizes in the monoclinic space group P2(1)/c in a unit cell of a=0.85257(12) nm, b=2.5358(4) nm, c=1.15151(13) nm, beta=118.721(8)degrees, V=2.183.2(5) nm(3), Z=4, D-c=1.624 g.cm(-3), mu=1.367 mm (1). The complexes, free ligands and chloride copper(II) salt were each tested for their ability to inhibit the growth of two gram-positive (B. subtilis and S. aureus) and two gram-negative (Salmonella and E. coli) bacteria. The complexes showed good antibacterial activities against the microorganisms. The interaction between the complexes and calf thymus DNA in aqueous solution was investigated adopting electronic absorption spectroscopy, fluorescence spectroscopy, viscosity measurements and cyclic voltammetry. Results suggest that the two complexes can bind to DNA by intercalative mode. In addition, the result of agarose gel electrophoresis suggested that the complexes can cleave the plasmid DNA at physiological pH and room temperature. Mechanistic studies with different inhibiting reagents reveal that hydroxyl radicals, and a singlet oxygen-like copper-oxo species are all involved in the DNA scission process mediated by the complexes.