Polyoxometalates characterized

A templating method was presented to fabricate novel three-dimensional ordered macroporous silica materials ftinctionalized by polyoxometalates. Characterization of the products indicated that the starting XMo, remained intact regardless of the functionality of the polyanions, and their primary lacunry structures tended to get saturated. The future development of the method holds promise for the formation of advanced new materials with more novel properties, which can be applied in more wide fields. 

Marchal-Roch, C. Bayer, R. Moisan, J.F. Teze, A. Herve, G. Oxidative dehydrogenation of isobu-tyric acid Characterization and modeling of vanadium containing polyoxometalate catalysts. Top. Catal. 1996, 5,407-419. 

Polyoxometalates. As regards the synthesis and characterization of some POMs, special thanks are addressed to Dr. R. Contant (Universite Paris VI), Professor C.L. Hill, Dr. T.M. Anderson and Professor I.K. Hardcastle (Emory University, Atlanta), Professor U. Kortz (International University of Bremen), Professor M.T. 

THREE-DIMENSIONAL ORDERED MACROPOROUS HYBRID SILICA MATERIALS FUNCTIONALIZED WITH LACUNARY KEGGIN-TYPE POLYOXOMETALATES PREPARATION AND CHARACTERIZATION... 

Characterization of the XMo,-Si02 materials indicated that the synthesis produced three-dimensional ordered macroporous materials with highly dispersed polyoxometalates covalently incorporated within the wall structures. IR, UV/DRS, solid-state MAS NMR spectra confirmed that the polyoxometalates remained intact in the hybrid macroporous silica materials. At first, three solid XMOu-SiOj materials all exhibited two absorptions with maxima at ca. 200 and 260 nm, respectively (Figure 1). The former is stronger and... 

Guo Y. H., Yang Y., Hu C. W., Ordered macroporous hybrid silica based on lacunary Keggin-type polyoxometalates preparation, characterization and photochemical behavior, Qn press). 

A novel and simple one-step solid-state reaction in the presence of a suitable surfactant (PEG-400) has been developed to synthesize uniform polyoxometalate nanorods with an average diameter of ca. 20 nm and a length of up to 400 nm. Polyoxometalate nanoparticles were also prepared by one-step solid-state reaction at room temperature. The polyoxometalate nanorods and nanoparticles were characterized by IR, elemental analyses, XRD and TEM. The uniform nanoparticles have an average size of 8 10 nm. The possible formation mechanism of these polyoxometalate nanomaterials was speculated. 

In the decade or so since the first edition of this encyclopedia, there has been a considerable growth in the synthesis and structural characterization of unusually large polyoxometalates. In most cases, these have stability in solution (NMR spectroscopy) as well as in the solid state, and can be considered as linked assemblies of polyoxoanion building blocks. 

The structure of [(Y0H2)3(C03)(A-a-PW9034)2]" [25]. (Reprinted with permission from T.M. Anderson, W.A. Neiwert, and C.L. HiU, Yttrinm polyoxometalates. Synthesis and characterization of a carbonate-encapsulated sandwich-type complex, Inorganic Chemistry, 42, no. 26, 8600-8602 (Figure 1), 2003. 2003 American Chemical Society.)... 

An, H., Xiao, D., Wang, E. et al. (2005) Open-framework polar compounds synthesis and characterization of rare-earth polyoxometalates (C6NO2H5)2[Ln(H2O)5(CrMo6H6O24)] 0.5H2O (Ln = Ce and La). European Journal of Inorganic Chemistry, 854-859. 

Ying Lu received a Ph.D degree from Northeast Normal University in 2005 under the supervision of Professor Enbo Wang. From 2006 to 2008 she worked as a Postdoctoral Fellow at the University of Ulm with Professor Dirk Volkmer. Currently she is an Associate Professor in Northeast Normal University. Her research is focused on the synthesis, structure and characterization of polyoxometalate-based organic-inorganic hybrid materials. 

The present review focuses first on actinide complexes of polymolybdates (section 2) and pol5durrgstates (section 3) that have beetr isolated and structurally characterized. There are currently no reported actinide polyvanadates, -niobates, or -tantalates. A final section (4) summarises solution studies of equilibria between actinide cations and polyoxometalate anions. 

Figure 15. Crystal structure of Compound 121 illustrating the importance of hydrogen bonding between cyclopentadienyl protons and the negatively charged polyoxomolybdate anion. [Reprinted from J. Organomet. Chem.. 488. C4 (1995) P. L. Veya and J. K. Kochi, Structural and spectral characterization of novel charge transfer salts of polyoxometalates and the cationic ferrocenyl donor. Copyright 1995, with kind permission from Elsevier Science SA, Lausanne, Switzerland]...

The explosion of activity and subsequent literature in the polyoxometalate field during the past two decades may reflect the increasing access to reliable methods of characterization in solution (multinuclear NMR) and the solid state (X-ray diffraction), but is certainly stimulated by the realization that there are few fields of science to which these complexes do not have important applications. One result of this expansion has been the necessity to devote two chapters to the chemistry of polyoxometalates one focusing on structure and one on reactivity instead of the single chapter in the original Comprehensive Coordination Chemistry (CCC, 1987). 

C. R. Mayer, P. K. Herson, R. Thouvenot, Organic-inorganic hybrids based on polyoxometalates. 5. synthesis and structural characterization of bis(organophosphoryl)decatungstosilicates [7-Si Vi,O3 ((RI O)2l, Inorg. Chem. 38 (1999) 6152. 

M. D. Ritorto, T. M. Anderson, W. A. Neiwert, C. L. Hill, Decomposition of A-type sandwiches. Synthesis and characterization of new polyoxometalates incorporating multiple d-electron-centered units, Inorg. Chem. 43 (2004) 44. 

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