Rare Earth Polyoxometalate Complexes

Northeast Normal University, 5268 Renmin Street, Changchun, 130024, P.R. China. Email luy968 nenu.edu.cn and wangenbo public.cc.jl.cn 

For the preparation of RE-POM complexes, traditional aqueous solution synthesis and hydrothermal synthesis [2] are the two main synthetic methods. In traditional aqueous solution synthesis, reactions are carried out in the temperature range from room temperature to the boiling point of water, and in general start from plenary or lacunary POMs and simple RE salts. Hydrothermal reactions typically proceed in the temperature range 120-200 C under autogenous pressure, and usually use simple metal salts of all the required elements as the starting materials. As different solubility problems are minimized under hydrothermal conditions, the 

Rare Earth Coordination Chemistry Fundamentals and Applications Edited by Chunhui Huang 2010 John Wiley Sons (Asia) Pte Ltd. ISBN 978-0-470-82485-6 

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The first systematic studies of polyoxometalate—rare-earth complexes were published in 1971 (Peacock and Weakley, 1971a, 1971b). Two classes of polytungstate complexes were described and these can now be seen to have common structural features. The complexes of Y, La, Ce(III and IV), Pr, Nd, Sm, Ho, Er, and Yb in which R W = 1 10 were readily formed by reaction of WO - with the appropriate rare-earth salt, but are stable only within the pH range 5.5-8.5. More recent 183W-NMR studies (Inoue et al., 2003) indicate that in solution the anions containing the heaviest R (Tm, Yb and Lu) are partially decomposed. 

Interest in polyoxometalate complexes of the rare earths has been driven to a large extent by their photophysical and photochemical properties. Table 1 lists several reviews. In general, photoexcitation into LMCT (O -> W, O -> Mo) bands results in intramolecular energy transfer to the rare earth with subsequent emission and luminescence. 

Polyoxometalate anions, especially those of hexavalent molybdenum and tungsten interact with rare-earth cations to generate a seemingly endless variety of complexes in which the rare earths function as encrypted cations, as core heteroatoms, or as linkers of polyoxometalate fragments to yield discrete anionic assemblies currently incorporating as few as 8 and as many as 164 metal centers,... 

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