Syntheses and structures of bicopper(II) complexes bridged by N-(5-chloro-2-hydroxyphenyl)-N′-[3-(dimethylamino)propyl]oxamide: Cytotoxic activities, and reactivities towards DNA and protein

Two new binuclear copper(II) complexes bridged by N-(5-chloro-2-hydroxyphenyl)-N′-[3-(dimethylamino)propyl]oxamide (H3L), and end-capped with 4,4′-dimethyl-2,2′-bipyridine (Me2bpy) or 2,2′-diamino-4,4′-bithiazole (dabt), respectively, namely [Cu2L(H2O)(Me2bpy)][Cu2L(CH3OH)(Me2bpy)](ClO4)2·(CH3OH)0.7 (1) and [Cu2L(CH3OH)0.25(dabt)]ClO4·(H2O)1.5 (2), have been synthesized and characterized by single-crystal X-ray diffraction. In complex 1, the dissymmetric unit of it contains two bicopper(II) cations, the cis-L3− ligands bridge two copper(II) ions with the corresponding separations of 5.1881(11) Å (Cu1···Cu2) and 5.2193(11) Å (Cu3···Cu4), respectively. In complex 2, the L3− ligand is adopting a cis conformation with the Cu···Cu distance of 5.2409 (7) Å. Through π–π stacking and hydrogen bonding interactions, the two bicopper(II) complexes are assembled to 3D supramolecular structures. Cytotoxic activities, and the reactivities towards DNA and protein of the two bicopper(II) complexes are investigated. The results suggest that the two bicopper(II) complexes interact with HS-DNA in the mode of intercalation, and the DNA-binding abilities are consistent with cytotoxic activities following the order of 2 > 1. The protein binding ability has been monitored using bovine serum albumin (BSA) as model protein.