| From the standpoint of molecular design, we attempt to make use of saturated and lacunary polyoxometalates derived from Wells-Dawson type anions as building blocks to design and synthesize diverse structural organic-inorganic composite compounds and polymers coordinated by RE ions. These compounds were characterized by single-crystal X-ray analysis, and executed properties study. The results describe as following:Chapter 1, Syntheses, Characterization and Crystal Structure of a Charge-Transfer Polyoxometalate Derived from Wells-Dawson AnionA charge-transfer polyoxometalate, (-H6P2W18O62·3(CH3)2NH·H2O (1), between the octadecatungstodiphosphorate (-H6P2W18O62·nH2O and the organic substrate dimethylamine, has been synthesized and characterized. The single-crystal X-ray structure analysis reveals that it crystallizes in a monoclinic system, space group P21/c with a = 12.964(3), b = 13.621(3), c = 41.559(8)?, ( = 90.02(3), V = 7338(3) ?3, and Z = 4, Dc = 4.094 g·cm-3, GOF = 1.106, F(000) = 7808, R1 = 0.0750,wR2 = 0.1772. There is weak interaction between dimethylamine and polyanion. The compound exhibits intensive photochromism. ESR spectra show that electrons can transfer from organic groups to inorganic subunits. Chapter 2, Syntheses, Characterization and Crystal Structure of a Polyoxome- talate-Based Composite Compound Derived from Wells-Dawson AnionA polyoxometalate-based composite compound of [{Y(DMSO)5(H2O)3}- {Y(DMSO)8}] [P2W18O62]·2DMSO·2H2O (2) was synthesized and characterized viaelemental analysis, IR and single-crystal X-ray diffraction analysis. The title compound crystallizes in a monocline lattice, P21/c, with a = 1.7614(4) nm, b = 3.1527(6) nm, c = 2.1523(4) nm, ( = 90.40(3)°, V = 11.963(4) nm3, Mr = 5803.06, Z = 4, Dc = 3.222 g/cm3, μ= 18.566 mm-1, F(000) = 10464, R = 0.0745 and wR = 0.1438. The result of crystal structure analysis indicates that, both Y3+ ions are eight-coordinate and the coordination polyhedra around two Y3+ ions attribute to bicapped distorted trigonal prism; RE coordination ions interact with polyanion by way of ionic band. Cyclic voltammetry of the compound (1mM, pH = 5.5) in the presence of Na2SO4(0.1 M) reveals five reversible or quasi-reversible (one, one, one, one, two electron) reductions, with decreasing the pH value, the later two steps would be combined with one two-electrons-reduction step. Chapter 3, Self-Assembly of 1D Polyoxometalate-Based Polymer Derived from Wells-Dawson AnionTwo composite compounds, [{Ce(DMF)4(H2O)3}{Ce(DMF)4(H2O)4}(P2W18O62)] (H2O (3) and [{La(DMF)6(H2O)}{La(DMF)4.5(H2O)2.5}(P2W18O62)] (4), have been constructed at room temperature and characterized by IR, UV and ESR spectroscopy, and single crystal X-ray structural analyses. Single crystal X-ray structural analyses reveal that, compound 3 crystallizes in a monocline lattice, Cc, a = 18.929(4)?, b = 22.086(4) ?, c = 26.501(5) ?, ( = 101.97(3)°, V = 10838 ? 3, Z = 4, μ= 19.959 mm-1, R1 = 0.0796,wR2 = 0.2034; compound 4 crystallizes in a monocline lattice, Cc, a = 18.897(4) ?, b = 22.036(4) ?, c = 26.556(5) ?, ( = 102.20(3)°, V = 10866 ? , Z = 4, T = 293K, μ= 19.861 mm-1, R1 = 0.0402,wR2 = 0.0995; through bridging RE-μ-Ot bonds the adjacent polyanions are polymerized to 1D infinite linear chain, in which polyanions and RE coordination ions alternate exhibiting a linking model of -ACACAC-; two types of terminal oxygen atoms of Wells-Dawson polyanion located in "cap" and "belt" sites are involved in coordination with the RE3+ ions respectively. ESR spectra show that electrons can transfer from organic groups to inorganic subunits. UV spectrum suggests that the compounds are entirely disruptive in dilute solution. Chapter 4, Controlled Assembly of 0D and 1D Polyoxometalate-Based Composite Compound Derived from Wells-Dawson AnionA series of polyoxometalate-based composite compounds, [Gd(DMF)6- (H2O)2]2·[P2W18O62]·4DMF·2H2O (5), [{Ce(NMP)3(H2O)4}{Ce(NMP)3(H2O)3}- (P2W18O62)]·NMP·4H2O (6) and [{Gd(DMF)6...
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