Synthesis, Structure And Properties Of Rare-Earth Metals Derivatives Based On Arsenotungstates Or Phosphotungstates

Polyoxometalates（POMs） are well-known metal-oxo clusters with the adjustable structures, sizes, compositions and other characteristics such as attractive thermal and oxidative stability, high proton acid property, excellent proton transfer toward oxygen donors and false liquid phase behavior. Rare earth elements with unique 4f electronic configuration, display long-life fluorescence, and that which can be used for the preparation of magnetic materials, especially single molecule magnet（SMM）. POMs-based rare earth derivatives are prepared by combining POMs and rare earth components by virtue of the assembly and coordination, which will endow them with new structural features and multiple functionalities as a result of blending of different functionalized components. Therefore, POMs-based rare earth derivatives attracted much attention due to their potential applications in the POMs and materials field. The introduction of rare earth ions into the POMs system possibly increases the corresponding functions, providing a promising way to combine the POMs and rare earth components by coordination-driven self-assembly.This thesis mainly concerns on the construction and the fluorescence together with magnetic studies of POMs-based rare earth derivatives. The main contents are as follows:1) Eleven arsenotungstate based rare earth derivatives with oligomer, dimeric, 1D helical and 2D layer-like structures were prepared by the [As₂W₁₉O₆₇（H₂O）]^14- precursor and rare earth ions in the presence of malic acid ligands by regulating the stoichiometric ratio of reactants and pH environment. These compounds mainly display four kinds of structure. Among them, compounds 1Dy, 2Tb, 4Eu and 5Sm shows the long-life fluorescence, and 1Dy shows the possible SMM.2) A series of inorganic-organic hybrid double-tartaric bridging mono-lanthanide substituted phosphotungstate derivatives were synthesized by the reactions of [P₂W₁₉O₆₉（H₂O）]^14- precursor and rare earth ions in the presence of tartaric acid and tetramethyl ammonium counterions, which display reversible photochromisms, characteristic luminescence and magnetic properties of lanthanide components. Especially, compound 12 Dy exhibit excellent multiple functionalities with reversible photochromic, switchable luminescent and SMM. In addition, four different phosphotungstate derivatives based on Dy³⁺ ions with diverse configurations were obtained by adjusting the stoichiometric ratio of reactants, counterions and pH environment. Rare earth Dy³⁺ ions show different coordinated configurations, which have a close relationship with their fluorescence and magnetic properties.3) Two high-nuclearity Ce-cluster embedded phosphotungstate derivatives based dilacunary [P₂W₁₆O₅₉]^12- subunits 19 Ce and 20 Ce, ten mono-lanthanide substituted phosphotungstate monomers 21La³0Ho, seven phosphotungstate hexamers 31Ce³7Tb constructed by monolacunary Dawson-type [α₂-P₂W₁₇O₆₁]10- subunits and rare earth ions, together with six phosphotungstate hexamers nested one plenary Dawson-type [P₂W₁₈O₆₂]6- polyanion 38Eu⁴3Er, were synthesized by the reactions of [P₂W₁₅O₅₆]^12- precursor and rare earth ions in the presence of isonicotinic acid and tetramethyl ammonium counterions. Compound 20 Ce is the first example of POMs containing the highest-nuclearity rare earth cluster up to now, and which displays a 2D graphite-like framework and excellent proton conductivity. These hexameric POMs constructed by monolacunary Dawson-type [α₂-P₂W₁₇O₆₁]10- subunits were found for the first time, and these annular hexamers builded by the middle and heavy rare earth ions can recognize and capture a plenary Dawson-type [P₂W₁₈O₆₂]6- polyanion. In addition, these POMs-based rare earth derivatives based on lacunary Dawson-type subunits also exhibit characteristic fluorescence and magnetic behavior in relation to 4f-4f transition of rare earth ions.