Synthesis, crystal structure, DNA-binding properties, cytotoxic and antioxidation activities of several ternary copper(II) complexes with a new reduced Schiff base ligand

Three new ternary copper(II) complexes, [Cu2(phen)2(PDIMAla)(H2O)2](ClO4)2·CH3OH (1), [Cu2(dpq)2(PDIMAla)(H2O)2](ClO4)2·CH3OH (2) and [Cu2(dppq)2(PDIMAla)(H2O)2](ClO4)2·CH3OH (3) (phen = 1,10-phenanthroline, dpq = dipyrido[3,2:2′,3′-f]quinoxaline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine, H2PDIMAla = N,N′-(p-xylylene)di-alanine acid) have been synthesized and the complex 1 has been structurally characterized by single-crystal X-ray crystallography, spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements. The results indicate that the three compounds, especially the complex 3, can strongly bind to calf-thymus DNA (CT–DNA). The intrinsic binding constants Kb of the ternary copper(II) complexes with CT–DNA are 0.38 × 105, 1.4 × 105 and 7.8 × 105 for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the human hepatic (HepG2), human promyelocytic leukemia (HL60) and human prostate (PC3) cell lines. Investigation of antioxidation property show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals.