Assembly strategy of polyoxotungstates: nanosized clusters with SeIV/TeIV as non-conventional templates

This thesis focuses on the assembly of non-conventional templated polyoxotungstates, specifically on {SeO3} and {TeO3}, which results in the discovery of 47 new polyoxotungstate compounds from the isolated gigantic nanoscale cluster {M2Se9W118+nO416+2n} (M = Mn, Co, Ni or Zn, n = 0; M = Fe or Cu, n =1) to the supramolecular 1D chain {CuTeW17O60}n and 3D network {Ag18Te6W76O271Cl}n. This study demonstrated the complexity of “building blocks library” in polyoxotungstates chemistry in “one-pot” reaction as well as the possibility to assemble the discrete building blocks in a controlled manner, which still represents a big challenge to the inorganic synthetic chemists. The formation of ‘pure’ tungstoselenite and tungstotellurate building blocks can be affected by a few vital reaction variables including, but not limited to, pH, ionic strength, temperature and type of cations. Carefully screening and controlling the reaction conditions can lead to different building blocks which have unprecedented novelty as such types of building blocks have never been discovered before in conventional templated polyoxotungstates, e.g., the lacunary pentagonal unit {(WO7)W4} containing {Se2W29} and {Te3W43}, the layer-shaped [TenW6n+3O21n+12](6+2n)- (n = 1, 2, 3) and so on. Further these building blocks could assemble into various polyanions through different aggregate behaviours. The transition metal ions containing tungstoselenite or tungstotellurate clusters can be reasonably designed and isolated by using a “shrink wrapping” strategy and screening the synthetic parameters such as pH, temperature and ionic strength. These clusters are fully characterized by XRD, ESI-MS/CSI-MS and chemical analysis, IR, as well as by preliminary electrochemical studies. The synthetic methodology is also developed, the combination of building block strategy and stepwise synthesis methods lead to the isolation of a series of new polyoxotungstate compounds including gigantic cluster {Cu9Se12W174O630Cl3} which represents the largest polyoxotungstate cluster containing pentagonal unit {(WO7)W4}. These discoveries lead to a general new polyoxometalate building block approach and start a new field in polyoxotungstate synthesis