Synthesis, structure, cytotoxic activities and DNA-binding properties of tetracopper(II) complexes with dissymmetrical N,N′-bis(substituted)oxamides as ligands

To compare the cytotoxicities and the DNA-binding properties in tetranuclear complexes with different bridging ligands, two tetracopper(II) complexes with formulae of [Cu-4(oxbe)(2)Cl-2(bpy)(2)]center dot 4H(2)O (1) and [Cu-4(oxbm)(2)Cl-2(bpy)(2)]center dot 2H(2)O (2) were synthesized, where H(3)oxbe and H(3)oxbm stand for N-benzoato-N'-(2-aminoethyl)oxamide and N-benzoato-N'-(1,2-propanediamine)oxamide, respectively, and bpy is 2,2'-bipyridine. Complex 1 was characterized by elemental analyses, IR and electronic spectra and single-crystal X-ray diffraction. The crystal structure reveals the presence of the circular tetranuclear copper(II) cations which are assembled by a pair of cis-oxamido-bridged dinuclear copper(II) units through carboxyl bridges. The crystal structure of complex 2 has been reported in our previous paper. However, the bioactivities were not studied. Cytotoxicities experiments reveal that both the two complexes exhibit cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549, and complex 1 has the better activities than those of complex 2. The results of the interactions between the two complexes and herring sperm DNA (HS-DNA) suggest that the two complexes interact with HS-DNA in the mode of intercalation with the intrinsic binding constants of 3.93 x 10(4) M-1 (1) and 2.48 x 10(4) M-1 (2). These results indicated that the bridging ligands may play an important role in the cytotoxicities and the DNA-binding properties of tetranuclear complexes. (C) 2010 Elsevier B.V. All rights reserved.