| Polyoxometalates (POMs) are clusters which are composed of {MO6} octahedra by point, edge and side-sharing. POMs are of variety in composition and structure, which make them having potential applications in catalysis, medicine, magnetism, luminescence, nonlinear optics and proton conductivity etc.. Though POMs have been studied for nearly two hundred years, the mechanism of formation of POMs is still not fully clearly and usually described as self-assembly.In this thesis, we synthesized fifteen compounds based on POMs via normal water solution synthesis method, and structurally characterized them by elemental analysis, IR, XPS and single crystal X-ray diffraction. The electrochemical and magnetic properties have also been investigated. The main results are as follows:1. By participation of V2O5 and Na2WO4·2H2O in solution, we tried many experimental conditions and succeeded obtaining two sandwich-type, one banana-type and one Anderson-like POMs. Compounds 1 and 2 are both classical tetra-substituted Weakley-type POMs with vanadium serving as heteroatoms. Compound 3 is a banana-type POM with {VW9} and {VW6} clusters connected by two {Co3} units. Compound 4 is in an Anderson-like structure with a vanadium atom in the central position and the terminal oxygen atoms are replaced by acetic acid. We studied the electrochemical properties of all the four compounds and we have also done some basic magnetic property investigations of compounds 1, 2 and 3. Na10[Mn4(H2O)2(VW9O34)2]·34H2O (1) Na10[Co4(H2O)2(VW9O34)2]·30H2O (2) Na17[Co6(H2O)2(VW6O26)(VW9O34)2]·66H2O (3) Na6[VW6O22(CH3COO)3]·11H2O (4)2. Paradotungstate-B and sandwich-type POMs were used as building blocks and transition ions or transition coordination compounds were used as linkers, we synthesized five one-dimensional or two-dimensional compounds. Compounds 5 and 6 are one-dimensional structures based on the paradotungstate-B clusters and linked by copper or cadmium ions. Compound 7 is a two-dimensional structure based on paradotungstate-B clusters and cadmium ions. Compound 8 is composed of glycine copper unit and paradotungstate-B anion. Compound 9 and 10 are in isostructure with sandwich-type POMs as building blocks and the linkers are the same metal with the heteroatoms, thus there are five coordination environments for every transition metal ion. In addition, we have also studied the electrochemical properties of these compounds. Na8[Cu(H2O)2(H2W12O42)]·30H2O (5) Na8[Cd(H2O)2(H2W12O42)]·20H2O (6) Na7.4[Cd1.3(H2O)2(H2W12O42)]·24H2O (7) Na8(NH4)2[{Cu(OOCCH2NH2)2}2(H2W12O42)]·21H2O (8) Na4[Zn4(H2O)18WZn3(H2O)2(ZnW9O34)2]·26H2O (9) Na4[Co4(H2O)18WCo3(H2O)2(CoW9O34)2]·24H2O (10)3. By taking different POMs and organic ligands, we constructed five supramolecular compounds. We studied the detailed hydrogen bonds in the compounds and their influences to the crystal structures. [Cr(OH)6Mo6O18]·[Al(H2O)6]·10H2O·(11) [C6H6NO2]3[PW12O40]·2H2O·(12) Na3[C10H10O6]2 [PW12O40]·4H2O (13) [(C3H5N2)(C6H6NO2)(H3O)][H2W12O40]·H2O (14) Na8Cu2(CH3COO)4Cl2[V10O28]·18H2O (15)In summary, through the detailed characterizations and discussions of these compounds based on POMs, we found some systemic synthesis methods and structure properties, which are predictive to the architecture of POMs with the similar building blocks and linkers.
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