| The coordination complexes, synthesized by polypyridines and transition metals as raw materials, are more and more important as their various structures and extensive uses. The use foreground of these compounds will be extensive in the field of molecular discernment, nucleic acid probe, anti-tumour medicine, molecular catalysis and self-assemble etc. With the development of science and technology, science of biology has become more and more important. Because DNA is a main carrier of life information, in recent years it has excited great interest across of wide fields of scientific enthusiasm among scientists. This work studies the interaction between transition metal complexes with polypyridine species and DNA by optical spectral and electrochemical methods.In this paper, a series of polypyridine Schiff base ligands have been designed and synthesized. Some of them are symmetric and the others are asymmetric. They are listed as follows: 4,5-diazafluorene-9-one (dafo), product of dafo condensed with ethylenediamine (L1), product of dafo condensed with1,2-diamino-propan(L2), the two ligands of L1 and L2 are symmetric Schiff base ligands; there are three symmetric Schiff base ligands synthesized by 2-pyridine-carboxaldehyde and diamine: product of 2-pyridine-carboxaldehyde condensed with 1,2-diamino-propan (L3), product of 2-pyridine-carboxaldehyde condensed with 1,3-diamino-propan (L4), product of 2-pyridine-carboxaldehyde condensed with diethylene triamine (L5); there are seven ligands of 1,10-phenanthroline-5,6-dione (dione) species ligands: dione, product of dione condensed with p-aminobenzoic acid (L6), product of dione condensed with m-aminobenzoic acid (L7), product of dione condensed with o-aminobenzoic acid (L8), product of dione condensed with p-nitroaniline (L9), product of dione condensed with m-nitroaniline (L10), product of dione condensed with p-chloroaniline (L11), the ligands of L6~L11 are all asymmetric Schiff base ligands. The structures and electronic properties of these ligands have also been studied by experimental characterization and theoretical calculation in detail. By use these ligands, 22 speciesof new complexes with transition metal ions have been studied detailedly. They are: [Zn(dafo)2(H2O)2](NO3)2 1, [Zn(dafo)2(H2O)]2(ClO4)2 2, [Cu(dafo)2(H2O)2](OPA)2 (OPA = one o-phthalic acid valence anion) 3, [Cu(dafo)2(H2O)]2(ClO4)2 4, [Cu(dafo)2 (H2O)]2(ClO4)2 5, [Cu2(CH3COO)4(H2O)]2-2dafo 6, [2-μ-O-Co3(dafo)6](ClO3)2H2O 7, [ZnCl4]-2(Hdafo)·2(H2O) 8, [CoCl4]·2(Hdafo)·2(H2O) 9, [Ag(dafo)2NO3] 10, [Cu(dafo)2(en)](ClO4)2·2H2O (en = NH2-CH2-CH2-NH2) 11, [Cu(dafo)2(NH2-CH2-CH(CH3)-NH2)](ClO4)2-2H2O 12, [Ni(L4)Cl2]-2H2O 13, [Ni(L4XH2O)2](NO3)2 14, [Ni(L4)(H2O)2](C104)2 15, [Cu(L4)](NO3)2 16, [Co(L4)(H2O)2](NO3)2 17, [Cu(L5)Cl2]-H2O 18, [Co(L6)Cl2]-0.5H2O 19, [Co(L8)Cl2]·0.5H2O 20, [Co2(L9) Cl4]·1.25CH3COOH 21, [Co2(L10)3Cl4]·3H2O 22.The structures and photo-physical properties of these complexes have been investigated systematically by various methods including elemental analysis, X ray crystallography, infrared spectrum, UV spectrum, fluorescence spectrum, thermal analysis and theoretical calculation. It has been found that the two ligands of L1 and L2 all hydrolyze when they coordinate to the copper ion, which result in that dafo and the relevant amine coordinate with copper ion simultaneous. The complexes formed by dafo with transition metals possess various structures. Ligand dafo coordinates to metals not only as monodentate ligand, but also as bidentate ligand. In addition, dafo may form monounclear complexes or multinuclear complexes. And dafo maybe forms simple complexes, or sometimes it forms superamolucular or polymer complexes through hydrogen bonds and coordination bonds. The complexes 13~17 own abundant hydrogen bonds formed by ligand L4 with transition metals. When ligand L5 coordinates with Cu(II), a ring-closing reaction happens to it. It has been found that the electronic structures of the complexes including the same ligand are very similar. The experimental fact is that they have similar infrared spectrum, UV spectrum and fluorescence spectrum. The thermal decomposition of some complexes has been investigated by TG-DSC. Their thermal decomposition processes have been presumed by experimental facts. On the basis of the experimentation, the complexes 1,3, 4 were calculated by DFT-B3LYP/LANL2DZ in Gaussian-98w. The geometry structures of the three complexes were constructed according to their crystal structures. There isdefinite deviation of the calculation value from the experimental value, but these errors are all in the range of the permission of the calculation method. So theoretical calculation plays active guidance role in the prediction of the energy of atoms, molecules, and solid ground state. It can also play active guidance role in the prediction of bond lengths and bond angles.It has been found that the DNA binding mechanisms of complexes are relevant to the structures of ligands and the shape of complexes. In this paper, all the ligands bear planar aromatic heterocycle. So DNA binding mechanisms of complexes 1~22 are observed by UV spectrum, fluorescence spectrum and electrochemistry analysis. After all the complexes interact with DNA, the UV spectra of the complexes are all changed in different grade, including hypochromism effect, red shift and blue shift. On the basis of the experimental facts, that the complexes probably insert into DNA can be concluded. It is stepped-up that the probability of the complexes 3, 4, 5, 6, 7,8,10,13, 19, 20, 21, 22 inserting into DNA by fluorescence spectrum testing. It is interesting that the complex 19 behaves like molecular "light-switch" for DNA: in the absence of DNA, it is no fluorescence peak, but in the presence of DNA, it appears obvious strong fluorescence peak. The testing of the electrochemistry analysis makes the fact that the action mode of complexes 3, 4, 5, 6, 7,8,9,10 with DNA is inserting proved. The action mode of the other complexes with DNA need father experimental proofs.
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