Synthesis, Crystal Structure And Nuclease Activity Of 1,10-Phenanthroline-Copper And Acyclic Polyamine Ditopic Ligand Binuclear Copper Complexes

The research on artificial nucleases has been one of the most active frontiers of biochemistry and molecular biology. The investigation on DNA and transition metal complexes as the potential artificial nucleases is the significant branch of bioinorganic chemistry, and is of important theory and application values. First, we can understand the catalysis mechanism and the role of the metal in it through studying the transition metal complex as the model of natural nucleases; second, the reagent of high efficiency and specific recognition can be used as the molecular biological tool and utilized in biological project. Third, as drug for the chemical therapy, the transition metal complexes also can be utilized to cure the tumor and genetic disease, as structure probe to study the structure of DNA and the interaction between DNA-binding protein and DNA. The mode of transition metal complexes cleave DNA is divided into the oxidative and hydrolytic mechanisms. The oxidative reagent is of higher efficiency, but it effect on DNA is destructive; the hydrolytic artificial nucleases just hydrolyze the phosphodiester bond of nucleic acid chain to produce the adhesive end that can be utilized again. Therefore, the hydrolysis cleavage agents are of profound study and application values in gene project and molecular biology. In addition, the binuclear or multi-nuclear metal complexes possess the higher activities, which gradually overcome the disadvantage of lower activities of hydrolysis cleavage agents. The research on binuclear metal complexes as the hydrolysis cleavage agents has attracted more and more attentions. Base on such study background, we develop our work in the two aspects of exploring the oxidative and hydrofytic cleavage agents. We sum up the main research results as follows.1. The oxidative cleavage reagents are mainly the Cu, Zn and Mn complexes with 1,10-phenanthroline ligand. We chose the iminodiacetic acid (IDA) as the auxiliary ligand to synthesize the mixed-ligands copper complex of [Cu(phen)2(μ-O-DA)(Phen)]-(NO3)2.4H2O(I) and [Cu(phen)2(μ-IDA)Cu(Phen)](ClO4)2.CH3OH(II). The tructure of both complexes was characterized with element analysis, IR spectra and X-ray single crystal diffracmeter. The analysis of crystal structure show that two Cu ions in each complex have the same coordination sphere, but exhibit the different coordintaion geometry, though the coordination sphere are both CuN40. the polyhedron around CuII(l)can be described as a distorted trigonal bipyramid, and that around Cu"(2) is a distorted suqare pyramid. In both complexes, the IDA plays dual roles, as a tridentate./acvchelating ligand and as a bridge ligand linking two Cu centers. The coordination effect of carboxylate oxygen is different in that it is the bridgeing oxygen linked to two Cu ions in complex (I) and it is solely coordicated with Cul in complex (II). Therefore, there is no oxygen bridge in complex (II), the whole IDA molecular serve as the bridge ligand to link two Copper centers. The different n-n stacking modes exist in complex (I) and (II) because of the different coordination of carboxylate oxygen molecule. In complex (I) the 7t-7i stacking exist in the intermolecule, and in complex (II) the 1,10-phenanthrolines ligands of two neighbouring molecules are intercalated each other to form the strong intermolecular 71-71 stacking.The complexes of Cu(2-Cl-Phen)3(C104)2(I) and [Zn(Phen)3](C104)2.CH3CH20H.-H2CXII) with the stoichiometric ratio of metal and ligands of 1:3 were synthesized and characterized by IR, EA and X-ray diffractometry, where Phen=l,10-phenanthroline; 2-Cl-Phen= 2-C1- 1,10-phenanthroline. X-ray diffractometry analysis show that coordination configuration of Cu2+ and Zn2+ ions in two complexes is distorted octahedron with six coordinated N atoms from the phen and 2-Cl-Phen. The two complexes is left handed helix. The experiment results demonstrate that complex (I) at the concentration of 0.5mM can efficiently promote the cleavage of pBR322 DNA with the collaboration of H2O2 or ascorbic acid (H2A). The synergy of H2O2 between complex and H2O2 seems more effective that pBR322 DNA was decomposed into 400 bp fragments. The ultraviolet radiation with 253nm and 356nm wavelength can induce the complex cleave pBR 322 DNA. The control experiments indicate that the cleavage activity is not influenced by the wavelength.The other four metal complexes with 1,10-phenanthroline ligand, (Phen)2Cu2Cl4(I), Cu(Phen)(SO4)(H2O)2(II), [Cu2(Phen)4Cl2](ClO4)2.H2O(III) and Mn(Phen)2Cl2(IV), were obtained and characterized by EA, IR and X-ray diffractometry.2. Our group found that Mg-dien (dien, diethylenetriamine) can efficiently promote the cleavage of pBR322 DNA, which attracts our attention to ligand dien. Our work on hydrolytic cleavage reagents focused on the binuclear copper complexes with two diencoordinated units. The complex of [Cu2L(H20)(0H)](C104)3 was synthesized and characterized with IR and Uv-vis spectra, EA and molar conductivity, where L is 2,6-bis{[bis-(2-aminoethyl)-amino]methyl}-benzene synthesized according to the reference methods. At the condition of pH 9.10 and 37°C, the complex at the concentration of 0.5 mM cleave the pBR322 DNA with the apparent rate constant kObS of 1.92X10"4 s"1. The control experiments of anaerobic reaction, hydroxide radical scavenger (methanol, glycerol and DMSO) and malondialdyhyde-like products analysis indicate that the complex cleave the pBR322 DNA through a hydrolysis mechanism showing the obvious activities-pH dependence relation. In order to investigate the relationship between buffer pH values and reaction activities, we determined the structures of complex in the solution using potentiometric titration. The pot shows that the active species is [Cu2L(OH)(H2O)]3+ that is produced through the deprotonation of one of coordinated water molecules of complex. The DNA viscosity experiments illustrate that complex bind with DNA by a surface-binging mode. Based on all the experimental results, we supposed the possible reaction mechanism: the complex provides the double Lewis activation by coordination between phosphoryl oxygen and two Cu2+ ions with free coordination sites. At the same time, the metal-coordinated OH' as nucleophile attacks the phosphoryl. The collaboration of doublw Lewis activation and nucleophilic activation is attributed to the reaction acceleration that complex hydrolytically cleaves phosphodiester.With the bridge linking, the two metal ions in bridged binuclear complexes were draw to a reasonable position to provide more strong synergism. Especially for hydroxide-bridged binuclear complex, the second metal ion can help generating nucleophilic oxide by lowering the pKa of the bridging hydroxide that can provide more rapid rate acceleration. According to the theory fundament, we synthesized the double oxide-bridged binuclear copper complex [Cu2(|i-O-L)(u-OH)]-(ClO4)2-H2O, where L is 2,6-bis{[bis-(2-aminoethyl)-amino]methyl}-l-phenol. The complex structure was characterized using IR spectra, element analysis and X-ray single crystal diffractometry. The crystal structure show that the complex is monoclinic, space group P2(l)/c, crystal dataa=25.841(6)A, b=13.970(3)A, c=14.165(3)A, p=96.719(4)°, V=5078.3 (19) A3, Dx = 1.788 Mg.m'3, F(000)=2816, Z = 8. The coordination configuration around two Cu2+ ions is five-coordinated square pyramid. The asymmetric unit contains two...