Preparation And Biological Activity Studies Of Schiff Base Complexes Containing Pyrazolyl-Pyridine Ligand

In recent years,Schiff bases and their transition metal complexes have been widely studied because of their good biological activity.Many of the complexes showed significant antitumor activity and were considered as potential antitumor drugs.In this paper,a variety of Schiff base metal complexes containing pyrazolyl-pyridine ligands were designed and synthesized,and their interactions with DNA and in vitro cytotoxicity were systematically studied by spectroscopic method,agarosegelelectrophoresisandMTT（3-（4,5-dimethyl-2-thiazole）-2,5-diphenyltetrazole bromide）method.The specific contents are as follows:1.N-（（6-（1H-pyrazol-1-yl）pyridin-2-yl）methylene）benzohydrazide（pypzbeyz）wassynthesizedbythereactionof6-（pyrazol-1-yl）pyridine-2-carbaldehyde（pypc）with benzohydrazide,and reacted with Co（NO₃）₂·6H₂O、Ni（Cl O₄）₂·6H₂O、Cu（Cl O₄）₂·6H₂O and Zn Cl₂as ligands to obtain the four complexes,[Co（pypzbeyz）（NO₃）₂]（1）,[Ni（pypzbeyz）₂]（Cl O₄）₂·CH₃OH（2）,[Cu₃（pypzbeyz）₃]（Cl O₄）₂·（OCH₃）·CH₂Cl₂（3）and[Zn（pypzbeyz）Cl₂]·CH₂Cl₂（4）.The structures of complexes 1-4 were characterized by IR,UV,MS and X-ray single crystal diffraction.The results show that complex 2 crystallizes in the monoclinic system with a P2₁/n space group,and its central nickel（II）ion has a twisted octahedral geometry.Complex 3 has a trinuclear structure and crystallizes in the triclinic crystal system with a P-1 space group.The three central copper（II）ions of complex 3 are all in the shape of distorted trigonal bipyramidal geometry.Complex 4 crystallizes in the monoclinic system with a P2₁/c space group,and its central zinc（II）ion has a distorted trigonal bipyramidal geometry.The results of spectroscopic analysis results show that the complexes 1-4 may interact with DNA through the groove pattern,and polynuclear complex 3 showed good combining ability due to the synergistic action of the polymetallic center,and their binding constants in order of size was 3>2>1>4.The results of gel electrophoresis showed that polynuclear copper complex 3 had a good DNA cleavage activity,and more than 47%of superhelix DNA（typeⅠ）was cleaved into linear DNA（typeⅢ）at the concentration of 40μM.The mechanism studies indicated that the DNA cleavage process of complex 3may be dominated by singlet oxygen and Cu²⁺.Cytotoxicity studies showed that complex 2 and 3 had certain cytotoxicity to A549,EC109,MCF-7 and PC-3 cancer cell lines,among which complex 3 had better cytotoxicity with IC₅₀values of 13.133±1.118,10.561±1.024,9.895±0.995 and 17.547±1.244μM,respectively.2.N-（（6-（1H-pyrazole-1-yl）pyridine-2-yl）methylene）thiosemicarbazide（pypzthcz）was synthesized by the reaction of6-（pyrazol-1-yl）pyridine-2-carbaldehyde（pypc）with thiosemicarbazide,and reacted with Co（NO₃）₂·6H₂O、Ni（Cl O₄）₂·6H₂O and Cu（Cl O₄）₂·6H₂O as ligands to obtain the three complexes,[Co（pypzthcz）₂]（5）,[Ni（pypzthcz）]（Cl O₄）（6）and[Cu（pypzthcz）]（Cl O₄）（DMF）₂（7）.The structures of complexes 5-7 were characterized by IR,UV,MS and X-ray single crystal diffraction.The results show that complex 5 crystallizes in the monoclinic crystal system with a C2/c space group,and the central cobalt（II）ion has a twisted octahedral geometry.Complex 6 crystallizes in the monoclinic system with a P2₁/n space group,and its central nickel（II）ion has a distorted square plane geometry.Complex 7 crystallizes in the monoclinic system with a P2₁/n space group,and its central copper（II）ion has a distorted square plane geometry.Spectroscopic experiments show that complexes 5-7 may interact with DNA through groove mode,and the order of binding intensity to DNA was 6>7>5.In addition,the cleavage activity of complexes 5-7 was investigated by gel electrophoresis,the experimental results showed that complex 7 have good cleavage activity,when the concentration of the complex 7 was 20μM,more than 66%of superhelix DNA was cut for incision type（type II）,when the concentration of the complex 7 was 80μM,the cleaving efficiency reached 82%.The mechanism experiments revealed that both hydroxyl radical and Cu²⁺may be involved in the DNA cleavage process of complex 7.