Synthesis, Crystal Structure And Biological Activities Of Schiff Base Transition Metal Complexes

Over the past decades, schiff base metal complexes which endowed with significant biological activities have been received considerable attention. In this paper, three metal complexes with schiff base of quinoline-2-carboxaldehyde were synthesized. The DNA-binding, DNA cleavage and in vitro cytotoxicity activities of these metal complexes were also studied.1. The ligand quinoline-2-carboxaldehyde thiosemicarbazone (QTS) derived from thiosemicarbazide and quinoline-2-carboxaldehyde was synthesized. The cobalt(Ⅱ) complex [Co(QTS)2]·Cl·H2O and nickel(Ⅱ) complex [Ni(QTS)2]·Cl·CH3OH were synthesized and characterized by infrared spectrum, elemental analysis and X-ray crystal diffraction. The two complexes are both six-coordinate distorted octahedral geometry, The cobalt(Ⅱ) complex crystallizes in a triclinic system with space group P-1and nickel(Ⅱ) complex crystallizes in a monoclinic system with space group P2(1)/n. The interactions of the cobalt(Ⅱ) and nickel(Ⅱ) complexes with CT-DNA were investigated by electronic absorption spectra, CD spectra and fluorescence spectra. The results suggested that both of them bind to DNA through a groove binding mode. The gel electrophoresis experiment showed that the cobalt(Ⅱ) and nickel(Ⅱ) complexes both exhibited efficient DNA cleavage activity in the presence of ascorbate as a reductant agent. With the increasing of the concentration of the complexes, the supercoiled DNA (Form Ⅰ) decreased gradually and almost completely converted to nicked DNA (Form Ⅱ). At the concentration of32μM, the cobalt(Ⅱ) complex was able to convert96%of Form Ⅰ to Form Ⅱ and the nickel(Ⅱ) complex was able to convert98%of Form Ⅰ to Form Ⅱ. Moreover, in vitro cytotoxicity of the cobalt(Ⅱ) and nickel(Ⅱ) complexes against human lung cancer cell lines A549, human breast cancer lines MCF-7and human ovarian cancer cell lines SKOV-3were tested using cisplatin as a positive control by MTT method. The results indicated that the cobalt(Ⅱ) and nickel(Ⅱ) complexes were both more potent against MCF-7cell line and lower cytotoxicity against A-549cell line and SKOV-3cell line than cisplatin. 2. The copper(Ⅱ) complex [Cu(QHA)]Cl2with Schiff base derived from quinoline-2-carboxaldehyde and histamine was synthesized by the in-situ synthesis method. It has been characterized by various methods including infrared spectrum, elemental analysis and X-ray crystal diffraction. The complex [Cu(QHA)]Cl2is five-coordinate distorted trigonal bipyramid and it crystallizes in a monoclinic system with space group P2(1)/n. The interaction of the copper(Ⅱ) complex with CT-DNA was investigated by electronic absorption spectra, CD spectra and fluorescence spectra. The results suggested that it bind to DNA through a groove binding mode. Moreover, in vitro cytotoxicity of the copper(Ⅱ) complex against human lung cancer cell lines A549, human breast cancer lines MCF-7and human ovarian cancer cell lines SKOV-3was tested using cisplatin as a positive control by MTT method. The results indicated that the copper(Ⅱ) complex was more potent against MCF-7cell line and lower cytotoxicity against A-549cell line and SKOV-3cell line than cisplatin.