Dissertation > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Chemical elements and inorganic compounds > Nature

Syntheses, Crystal Structure and Properties of Novel Polyniobate and Polyoxometalate Based on Keggin Structure

Author LiJie
Tutor NiuJingYang;WangJingPing
School Henan University
Course Inorganic Chemistry
Keywords Compounds Anion Polyoxometalates Crystal structure Chemistry Major Polyoxometalate Henan University Scan rate Graduate Properties of
CLC O611.3
Type Master's thesis
Year 2006
Downloads 46
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In this thesis, we obtained three unprecedent isopolyniobates by precipitation-transformed method with A-8Nb6O19·nH2O (A = K or Na) as raw material. Meanwhile, polyoxometalates with Sandwich and saturated Keggin anion as building blocks have been synthesized by the normal techniques.(I) Using Cu2+ cation as template, we first synthesized three polyniobates, K(120Na4H23[ NaO8Cu24(Nb7O22)8]·106H2O (1), K16Na12H9[Cu25.5O8(Nb7O22)8]·73.5H2O (2) and K14 H22[KO8Cu25.5(Nb7O22)8]·45.5H2O (3), and characterized them by IR, ICP and the variable-temperature magnetic susceptibilities. The studies of magnetic properties of compound 1 show the presence of antiferromagnetic coupling between Cu2+ ions;(II) Two heteropolytungstates containing trivacant Keggin anion SbW9O339- have been obtained, [Na(H2O)]2H2[Mn2.5W1.5(H2O)10(β-B-SbW9O33)2]·28H2O (4) and Na-4H7[Na3 (H2O)6Mn3(Ac)2(α-B-SbW9O33)2]·20H2O (5). Compound 4 and 5 were charactered by element analysis and IR spectra. The results of IR spectra show the two anions still keep the backbone of trivacant Keggin-type anion;(III) Using plenary Keggin-type polyanion [CuW12O40]6-, [PMo12O40]3- and [BW12O40]5- as building block and using 2,2′-bpy and DMF as organic ligands, we have synthesized three organic-inorganic hybrid compounds and characterized them by IR, UV, and ESR spectroscopy, and studied by TG/DTA and CV, [Cu(2,2′-bpy)3]2H4[CuW12O40]·6H2O (6), {H[Ba(DMF)6PMo12O40]·(dma)}n (7) and [Ce(DMF)4(H2O)][α-BW12O40]·H2O·(HDMA)2 (8). The results of the single crystal X-ray diffraction analyses show these compounds present the structure of 0D, 1D zigzag linkage and 2D network, espectively. ESR spectra of powder of compound 7 after exposed to sunshine are typical of Mo5+. The results of cyclic voltammetry (CV) show that (a) [PMo12O40]3- and [BW12O40]5- anions are active centers for electrochemical redox reactions in solution, while corresponding cations have a small effect on the electrochemical properties; (b) pH value of the solution has great influence on the redox behavior of the polyanion of the

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