Solid state, polyoxoanion structure

M = Mn, Cu, Zn, Cd ) synthesized were studied by W NMR spectroscopy and it was indicated that the solid-state polyoxoanion structures of the diamagnetic Zn and Cd derivativesare preserved in solution. The charges on metal cations of the coordination sphere of polyoxometalates (POM) of V, Mo and W were calculated using the EHMO method, and obtained values were compared with the Mo and NMR chemical shifts of the corresponding nuclei as mentioned above. ... 

Heteropolyanions and isopolyanions are polymeric oxoanions (polyoxometalates) (2, 3, 5, 6). The structure of a heteropolyanion or polyoxoanion molecule itself is called a primary structure (5, 6, 77). There are various kinds of polyoxoanion structure (Section II.A. 1). In solution, heteropoly anions are present in the unit of the primary structure, being coordinated with solvent molecules and/ or protonated. Most heteropolyanions tend to hydrolyze readily at high pH (Section 1I.C). Protonation and hydrolysis of the primary structure may be major structural concerns in solution catalysis. Heteropoly compounds in the solid state are ionic crystals (sometimes amorphous) consisting of large polyanions, cations, water of crystallization, and other molecules. This three-dimensional arrangement is called the secondary structure. For understanding catalysis by solid heteropoly compounds, it is important to distinguish between the primary structure and the secondary structure (5, 6, 17). Recently, it has been realized that, in addition... 

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. 

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