Polyoxometalates defined

Polyoxoacids, defined, 41 117,118 Polyoxometalates defined,41 117,118 transition-metal-substituted, 41 224-225 Polyoxomolybdates, 41 193 Polyoxotetramelhyleneglycol, synthesis, 41 156-157... 

Figure 2.9 Schematic structure of two dif- (d) cube. The dpp parameter defines the aver-ferent polyoxometalate complexes with inter- age distance between the two oxygen-based esting coordination symmetry (a) LnW10 and square planes. The djn is the average 0-0 (b) [LnPd"12(AsvPh)8032]5-, and their coor- distance within the oxygen-based square dination polyhedra (c) square antiprism and planes.

To a large extent the discussion will be limited to those complexes that have a discernible solution chemistry (e.g., by spectroscopy). The boundary between metal-oxide lattices and solid-state materials incorporating known and new polyoxometalate structures is becoming less and less well defined. Although this is an interesting and important area, with many potential applications, it is beyond the scope of the present endeavor. 

Solid-state reference electrodes for potentiometric sensors are currently under research. The main problem to be faced in developing this type of electrode lies in connecting the ionic conducting (usually aqueous) solution with an electronic conductor. Since the reference electrode has to maintain a defined potential, the electrochemical reaction with components of the electrolyte has to be avoided. Oxides, mixed oxides, and polyoxometalate salts of transition elements can be proposed for preparing solid-state reference electrodes. Tested compounds include tungsten and molybdenum oxides (Guth et al., 2009). 

We shall define a composite polyoxometalate as one containing two or more polyoxoanion building blocks and linker atoms or groups. Although the stmctures of such composite species suggest that they can be rationally synthesized by combination of building block with linker, in many cases the complete structure is formed from mononuclear components in a one-pot reaction. ... 

Additional features of polyoxometalates impact some of the six limitations. First, polyoxometalates are oxidatively resistant as a great majority of them are composed of d° transition metal ions (most commonly W(VI), Mo(V), and/or V(V)) and oxide ions. Second, the unusually high stability of polyoxometalates coupled with the tunability of their catalytically relevant properties defines a considerable ability to avoid problems associated with intermediate oxidation states, p-oxo dimers, and product inhibition. Illustrations of two representative polyoxometalates, Wio0324 , an isopolyoxometalate (or isopolyanion) and (TM)XWii039 , a transition metal (TM) substituted heteropolyoxometalate (or heteropolyanion) in polyhedral notation are given in Figure 1. 

PFg, BF4, polyoxometalates (POMs), and even glucose oxidase (GOD) as the counter-anions (Fig. 4.14a, SWNT-IL-X) [56]. The properties of SWNT and the various anions were facilely and successfully delivered into the resulting compounds. For example, the rich redox activity was also successfully transferred into SWNT-IL-POM merely by a simple and facile anions exchange. The surface-confined SWNT-IL-POM shows three couples of well-defined redox waves at scan rates up to 2 V/s (Fig. 4.14b), which was presumably attributed from electron conduction of SWNT, ionic conduction of IL, and redox conduction of POM. It was unusuai for an often-seen compound in electrochemical systems. 

Polyoxometalates are well-defined inorganic metal-oxygen cluster anions, whose oxidizing power is influenced by the properties of the different metal atoms. Their straightforward synthesis enables them to be tailor-made for bleach reactions [45]. 

Polyoxometalates (POMs) are molecular nanosized polyanionic scaffolds, with multi-metal oxide structure and thus with a general motif being at the interface between molecular complexes and extended oxides.They offer well-defined models for the reactivity of metal bulk oxides, displaying, in addition, the typical tunability of the molecular species. 

DIMCARB upon preparation of the polyoxometalate solutions to form an electroinactive species. Fortunately, the adhered microparticles technique avoids prolonged contact with DIMCARB, thereby allowing weU-defined voltammetry to be observed. The initial process involved in the reduction of adhered microparticles of [Bu4N]4[SiWi204o](s) (oc, p, and y isomers) in DIMCARB is summarized as follows for the first reduction process ... 

In Chap. 2, metal nanoparticles (abbreviated MNPs) are introduced and defined as giant clusters of nanometer size with precise geometries resulting from the packing of atoms. - Ideally, their size and dispersity can be controlled during their synthesis. They can be covered with ligands, anionic stabilizers such as halides (see below), polyoxometallates, etc. or various polymer stabilizers that will define their solubility in organic solvent, water or fluorous solvent... 

Understanding fundamental uranyl polyoxometalate chemistry in solution and the SS is the 1st step to defining its future role in the development of new actinide materials and separation processes that are vital to every step of the nuclear fuel cycle. Many SS geometries of uranyl polyoxometalates were described, but the authors are only beginning to understand their chemical behavior, which thus far includes the role of templates in their self-assembly, and the dynamics of encapsulated species in solution This study provides unprecedented detail into the exchange dynamics of the encapsulated species in the SS through MAS NMR spectroscopy. ... 

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