Synthesis and structure of new tetracopper(II) complexes with N-benzoate-N'-[3-(diethylamino)propyl]oxamide as a bridging ligand: The influence of hydrophobicity on enhanced DNA/BSA-binding and anticancer activity.

Two new tetracopper(II) complexes bridged by N-benzoate-N'-[3-(diethylamino)propyl]oxamide (H3bdpox), and ended with 4,4'-dimethyl-2,2'-bipyridine (Me2bpy) or 2,2'-bipyridine (bpy), namely [Cu4(bdpox)2(Me2bpy)2](pic)2 (1) and [Cu4(bdpox)2(bpy)2](pic)2·2H2O (2) (where pic denotes the picrate anion) have been synthesized and characterized by X-ray single-crystal diffraction and other methods. In both complexes, four copper(II) ions are bridged alternately by the cis-oxamido and the carboxylato groups of two bdpox(3-) ligands to form a centrosymmetric cyclic tetranuclear cation, in which, the copper(II) ions at the endo- and exo-sites of cis-bdpox(3-) ligand have square-planar and square-pyramidal coordination geometries, respectively. The reactivity towards DNA/BSA suggests that these complexes can interact with HS-DNA through the intercalation mode and the binding affinity varies as 1>2 depending on the hydrophobicity, and effectively quench the fluorescence of protein BSA via a static mechanism. In vitro anticancer activities showed that the two complexes are active against the selected tumor cell lines, and the anticancer activities are consistent with their DNA-binding affinity.