Synthesis And Characterization Of P₂W₂₀-Heteropolyanion Containing Rare Earth Elements

The chemistry of polyoxometalate anions is the chemistry of isopolyanions and heteropolyanions. Generally speaking, polyoxoanions are water- and air- stable species of large size and prossess high ionic weight. Heterpoly compounds are more numerous and their structural and electronic proterties are easier to modify. These compounds have held sway in applied fields. At the beginning of work in this article, previous studies on history and application of polyanions chemistry were surveryed. From the finding material, we can see that the applied fields of polyanions has a great increase.The applied fields of heteropolyanions is wide. The compounds are good catalysts in both acid-catalyzed and oxidation reactions. The applied fields of heteropolyanions also include analytical chemistry, materials science, medicine, and other fields.In recent years, the internal chemists have synthesizedsome heteropolyanions containing rare earth elements, and studied in antiviral , anti-HIV , and antitumoral activity of heteropolyanions. Experimental results indicated these compounds have good effects in these fields.The P2W2i heteropolyanion gives two lacunary forms [P2W20O70(H2O)2]10-( P2W20) and [P2W19O69H20]14-( P2WI9) by losing one or two W=0 groups from the equatorial belt. Some foreign chemists have synthesized serials heteropolyanions of P2W20, such as P2W20Bi, P2W20Sn , and P2W20Ce , et al, but the report on research and the application of P2W20 heteropolyanion containing rare earth elements is little.Chapter 1 is intended to give a general review of the field: synthetic methods, common structures, properties, and applications.Chapter 2 is about the synthesis and characterization of P2W20-heteropolyanions containing rare earth elements.The Keggin-type polyanions [PW12040]3- are degraded by aqueous bases affording, as a first step, the corresponding socalled lacunary heteropolyanion [PW11O39]7- by removal of one WO group. The sodium undecatungstophosphate is also prepared with a new direct procedure, the sodium tungstate dihydrate andanhydrous disodium hydrogenophosphate are dissolved in the water, the solution is heated to 70-80℃ and titrated exactly with concentrated nitric acid to pH 3.0 with vigorous stirring. By combining K7[PW11O:i9] (aq) and Na8[HPW9034](aq), we can synthesize pure K14[P2W19O69(OH2) ]. From K,4[P2W19O69(OH2)], we can prepare K10[P2W20O70(OH2)].24H20. Then we first prepared the P2W20Ln-heteropolyanions containing rare earth elements :Ln=Sm, Eu, Er, Dy, Tb, Gd, Yb, Y.Chapter Sis about the photoinduced coloration of complex of the P2W20-heteropolyanions containing rare earth elements and PVA. Experimental result indicated P2W20Ln/PVA had the photoinduced coloration.The new ideas of this work are listed as following:( I ) we first prepared the P2W20-heteropolyanions containing rare earth elements :Ln=Sm, Eu, Er, Dy, Tb, Gd, Yb,Y.( II ) we first studied the properties of photoinduced coloration of P2W20K/PVA and P2W20Ln/PVA.