Synthesis, crystal structure, cytotoxic activities and DNA-binding properties of new binuclear copper(II) complexes bridged by N,N′-bis(N-hydroxyethylaminoethyl)oxamide

Two new μ-oxamido-bridged binuclear copper(II) complexes with formulae of [Cu2(heae)(pic)2] (1) and [Cu2(heae)(Me2phen)2](ClO4)2 · H2O (2), where heae and pic stand for the anion of N,N′-bis(N-hydroxyethylaminoethyl)oxamide and 2,4,6-trinitrophenol, respectively, and Me2phen represents 2,9-dimethyl-1,10-phenanthroline; have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectra studies. The crystal structures of the two binuclear copper(II) complexes have been determined by X-ray single-crystal diffraction. In both the two binuclear complexes the central two copper(II) atoms are bridged by trans-heae. In complex 1 the coordination environment around each copper(II) atom can be described as a distorted octahedral geometry, while in complex 2 each copper(II) atom displays a square-pyramid stereochemistry. Hydrogen bonding and π–π stacking interactions link the binuclear copper(II) complex 1 or 2 into a 3D infinite network. The cytotoxicities of the two binuclear copper(II) complexes were tested by Sulforhodamine B (SRB) assays against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549. Both of the two binuclear copper(II) complexes exhibit potent cytotoxic effects against SMMC-7721 and A549 cell lines. The interactions of the two binuclear complexes with herring sperm DNA (HS-DNA) are investigated by using absorption and emission spectra and electrochemical techniques and viscometry. The results suggest that both the two binuclear copper(II) complexes interact with HS-DNA in the mode of intercalation with the intrinsic binding constants of 1.73 × 105 M−1 (1) and 1.92 × 106 M−1 (2). The influence of structural variation of the terminal ligands in the binuclear complexes on DNA-binding properties is preliminarily discussed.