Biomimetic Synthesis And Properties Of Tungsten Oxygen Transferase Activity Of The End Of The Ligand Field

Tungstoenzymes play an important role in the global cycles of nitrate,carbon,and sulfur. X-ray structure analyses for tungstoenzymes indicated that the metal tungsten was coordinated to the cofactor through the dithiolene sulfers and formed the active site. Structurally characterized synthetic analogs of the active sites of W-containing enzymes are essential for the interpretation of biochemical properties and catalytic activity of tungstoenzymes. So biomimetic synthesis and biochemical mechanism study of active cofactor of tungstoenzymes attracted considerable attention. In this thesis,a series of biomimetic complexes of the cofactor of tungstoenzyme with cate-chol and o-phenylenediamine organic ligands have been synthesized and characterized by means of spectra and X-ray analysis. The main points are as follows:1, Cis-dioxo-catecholatotungsten(VI) complex (NH₃CH₂CHNH₂CH₃)₂[W^VIO₂ (OC₆H₄O)₂] (1) is obtained with chiral protonated 1,2-propanediamine by the reaction of tetrabutyl ammonium decatungstate with catechol in the mixed solvent of CH₃OH, CH₃CN at room temperature.The crystal structure of complex was determined by X-ray diffraction structural analysis.The results show that complex belongs to mono-clinic system with space group P2_1/n, and studied by IR, ¹HNMR and UV-vis.The NMR studies on the interaction of the title complex with ATP reveal that ¹H chemical shifts of 1,2-propanediamine and catechol with and without ATP exhibit distinct difference, the reduction of W(VI) to W(V) occurs when the title complex is dissolved in D₂O and the W(V) is oxidized again when ATP solution is mixed with original solution and the hydrolysis of the catecholato ligand take places at mean time being monitored by ¹H NMR.2,Cis-dioxo-catecholatotungsten(V) complex (NH₂CH₂CH₂NH₃)₄[W^VO₂ (OC₆H₄O)₂]₂(NH₃CH₂CH₂NH₃) ? H₂O (2) is synthesized at room temperature by the reaction of tetrabutyl ammonium decatungstate with catechol in the mixed solvent of CH₃OH, CH₃CN and NH₂CH₂CH₂NH₂.The crystal structure of complex (2) was determined by X-ray diffraction structural analysis.The results show that complex (2) belongs to monoclinic system with space group P2_1/c. Compared complex (2) with complexes (NH₂CH₂CH₂NH₃)2[W^VIO₂(OC₆H₄O)₂], (NH₂CH₂CH₂NH₃)_2.5[Mo₀.5^V W^VIO₂(OC₆H₄O)₂] and (NH₂CH₂CH₂NH₃) ₃[Mo^VO₂(OC₆H₄O)₂], it is found that the variance of the oxidation states and EPR spectra of center metal ions has no influence on the coordination feature. It could be suggested that the coordination structure of W have no changes in the processing of electron transfer of tungsten-containing enzymesfrom the result of the similarity of the EPR spectra the complexes and flavoenzyme from milk.3, The cis-dioxo tungsten(VI) complex, [(NH2CH2CH2NH3)2WVIO2(NHC6H4 NH)2]2(NH2CH2CH2NH2)-H2O (3) is synthesized at room temperature by the reaction of sodium tungstate with o-phenylenediamine in the mixed solvent of CH30H, H2O and NH2CH2CH2NH2.The crystal structure of complex was determined by X-ray diffraction structural analysis. The results show that complex belongs to monoclinic system with space group P21/c.Compared the complex with its analogous biomimetic complexes of the cofactor of molybdoenzymes and tungstoenzymes ,it is found that the variance of the coordination atoms and the metal ions center has no influence on the coordination feature,and exhibits distored octahedral coordination with cis-dioxo o-phenylenediamine.From our studies, we found that the title compound haven't synthesized under the same reaction condition as its analogous catecholato-tungsten and -molybdenum complexes.In addition, C6H4(NH2)2·2HCl (4) with red (4a) and pale brown(4b) crystals were synthesized at room temperature by the reaction of o-phenylenediamine with hydrochloric acid in the mixed solvent of CH3OH and H2O, meanwhile, phenazine-2,3-diamine (5) with nut-brown of o-phenylenediamine dimmer was synthesized, and their crystal structures were determined by X-ray diffraction method. The result in...