Tungsten Biomimetic Synthesis And Characterization Of The Activity Structure Factor

Tungstoenzymes played intimate roles in the global cycles of nitrate, carbon and sulfur. Structurally characterized synthetic analogs of the active sites of W-containing enzymes were 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.X-ray structure analyses for tungstoenzymes indicated that the metal W was coordinated to the cofactor through the dithiolene sulfers and formed the active site. Polyphenols were antioxidants, which were known to influence bioavailability of metals in the body. In addition, metal-catechol complexes could exhibit interesting electronic effects associated with the variable state of metal and charge distribution of ligand, due to the delicate balance in energy between the frontier quinine and metal orbitals. They were believed to be a model for the biological transport of ion and catechol/quinine related enzymes and biomolecules. In this thesis, a series of biomimetic complexes with catechol or 2,3-dihydroxynaphthalene ligand of tungstoenzyme cofactor have been synthesized and characterized by means of spectrum,X-ray analyses. The main points were as follows:1,Four different complexes (NH₂CH₂CH₂NH₂)₂{Na₂[μ₂-(C₆H₆O₂)₂](C₆H₄OOH)₂}(1),[NH₃CH₂CH(NH₂)CH₃]{WO₂(C₆H₄O₂)₂Na[NH₂CH₂CH(NH₂)CH₃]}_∞(2),{Na₂[(C₆H₄O₂)₂](C₆H₄OOH)₂}(H₃NCH₂CH₂CH₂NH₃)₂(3),{Na₂(μ₂-OH)[WO₂(C₆H₄O₂)₂]₂[C₃H₃N₂][NH₃(CH₂)₃NH₃]}·2CH₃OH(4)were synthesized bythe reaction of Na₂WO₄·2H₂O with catechol in the mixed solvent of CH₃OH,CH₃CN, with NH₂CH₂CH₂NH₂, NH₂CH₂CHNH₂CH₃, and NH₂CH₂CH₂CH₂NH₂ added respectively.(a) Structural characterization by x-ray diffraction. The crystal structure results showed that complex1 was consisted of two NH₂CH₂CH₂NH₂ and a discrete molecular {Na₂[μ₂-(C₆H₆O₂)₂](C₆H₄OOH)₂} cluster, while complex2 and 4 exhibited one-dimensional (1D) infinite chain along theα-axis, and the neighboring chains were linked by van der vaals force and H-bonds. Complex3 was composed of two [H₃NCH₂CH₂CH₂NH₃]²⁺and a discrete molecular {Na₂[(C₆H₄O₂)₂](C₆H₄OOH)₂} cluster.(b) The comparison of ¹³C NMR spectrum of the complex4 in solid state with that in solution indicated that the rapid exchange between the bridgingμ₂-(C₆H₆O₂) and terminal (C₆H₄OOH)^- ligands was presented in solution.2,Three different complexes {Na(CH₃O)[H₃N(CH₂)₂NH₂]₂}[WO₂(C₁₀H₆O₂)₂](5), [H₃N(CH₂)₃NH₃]₂[WO₂(C₁₀H₆O₂)2](6)å'Œ{WO₂(C₁₀H₆O₂)₂(C₅H₁₁N₂)₂[H₂N(CH₂)₃NH₂]}(7)were synthesized by the reaction of Na₂WO₄·2H₂O with 2,3-dihydroxynaphthalene in themixed solvent of CH₃OH,CH₃CN, with NH₂CH₂CH₂NH₂, and NH₂(CH₂)₃NH₂ added respectively.(a) Structural characterization by x-ray diffraction. The crystal structure results showed that complex5 exhibited one-dimensional (1D) infinite chain. In every chain, there were some [WO₂(C₁₀H₆O₂)₂]^2- units, which were linked byÏ€-Ï€stacking interaction.Complex6 was a discrete molecule and there existed six-member ring organic molecules in complex7.(b) The ¹H and ¹³C NMR spectrum of the complex7 in D₂O indicated that there existed six-member ring organic molecules.