Synthesis, structures, anticancer activities and DNA-binding properties of new dicopper(II) complexes bridged by N-benzoato-N′-(2-amino-2-methylethyl)oxamide

Abstract

Two new dicopper(II) complexes bridged by N-benzoato-N′-(2-amino-2-methylethyl)-oxamidate (oxbm), and end-capped with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen), respectively, namely [Cu2(oxbm)(bpy)(H2O)2](pic) (1) and [Cu2(oxbm)(phen)(H2O)(CH3OH)](pic) (2) (where pic = 2,4,6-trinitrophenol), have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR, electronic spectra, and X-ray single crystal diffraction. In the two complexes, the central copper(II) atoms are bridged by cis-oxbm3− with Cu···Cu separations of 5.1815 A (1) and 5.1672 A (2), respectively. Atoms Cu1 and Cu2 are both in distorted square-pyramidal coordination geometries. The three-dimensional supramolecular structures in complexes 1 and 2 are built up by classical and non-classical hydrogen bonding chains. The interactions of the two dicopper(II) complexes with herring sperm DNA (HS-DNA) are investigated by using electronic and fluorescence spectra, electrochemical techniques, and viscometry. The results show that the two dicopper(II) complexes interact with HS-DNA in the mode of intercalation and complex 2 possesses stronger intercalating ability. Cytotoxicities experiments reveal that the two dicopper(II) complexes exhibit cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549. Cytotoxic activities follow the order 2 > 1, which are thought to be related with their DNA-binding affinities. The influence of the substituent on terminal ligands in the dicopper(II) complexes on DNA-binding properties and anticancer activities is preliminarily discussed.