Polyoxometalate POM

A reaction of mixed molybdenum polyoxometalates (POMs) with cyanine dye has been used for highly selective and sensitive spectrophotometric determination of phosphorus(V) and arsenic(V). Color of the solution is considerably changed by reaction of Keggin POMs with styrene cyanine dyes. Derivatives of l,3,3-threemethyl-3//-indol - astrazone violet (AV 3R), astrazone rose, astrazone yellow, astrazone red were investigated. 

Ionic associates (lA) of polyoxometalates (POMs) with threephenylmethane dyes remain as perspective analytical forms for the determination of some nonmetals including P(V), As(V) and Si(IV). Several reasons hinder to the improvement of analytical characteristics of these reactions. Separation of dye excess and its lA with reagent are most important Procedure for extractive separation is often timeconsuming, complex and does not allow complete separation from reagent excess. 

The development of catalysts for the oxidation of organic compounds by air under ambient conditions is of both academic and practical importance (1). Formaldehyde is an important intermediate in synthetic chemistry as well as one of the major pollutants in the human environment (2). While high temperature (> 120 °C) catalytic oxidations are well known (3), low temperature aerobic oxidations under mild conditions have yet to be reported. Polyoxometalates (POMs) are attractive oxidation catalysts because these extensively modifiable metal oxide-like structures have high thermal and hydrolytic stability, tunable acid and redox properties, solubility in various media, etc. (4). Moreover, they can be deposited on fabrics and porous materials to render these materials catalytically decontaminating (5). Here we report the aerobic oxidation of formaldehyde in water under mild conditions (20-40 °C, 1 atm of air or 02) in the presence of Ce-substituted POMs (Ce-POMs). 

Polyoxometalates (POMs) have been the object of growing interest as photocatalysts for the oxidation or reduction of organic or inorganic compounds [225-230], Many of these POM systems share the same general photochemical characteristics as semiconductor photocatalysts. For example,... 

The versatility and accessibility of polyoxometalates (POMs) have led to the various applications in the fields of structural chemistry, analytical chemistry, surface science, medicine, electrochemistry, photochemistry, and catalysis. Especially, POMs have received much attention in the area of oxidation and acid catalysis [25-31]. Several categories of POMs are formed by proper selection of the starting components and by the adjustment of pH and temperature. Typical examples are shown in Figure 13.1 (i) isopolyoxometalates of the general formula, MxO> 1, produced by condensation... 

The intercalation of anionic species into LDHs is an interesting alternative for the immobilization of catalytic complexes. Special attention is being paid to LDHs containing bulky and stable anions, e.g. polyoxometalates (POMs), since they can give rise to a wide range of microporous materials [4]. Many years ago, Pinnavaia et al. reported the intercalation of POM anions into LDHs, and found that the products showed significant photo-catalytic activity in the oxidation of isopropanol to acetone in the presence... 

In this context, much effort has also been invested in controlling the nuclearity of the catalyst ensemble through the selection of its precursor. One area in which considerable progress has been made involves the adsorption of polynuclear clusters onto supports [33]. Examples involving the immobilization of small, preformed polynuclear clusters on supports are the reactions of carbonyl clusters of the late metals [16, 34], the binding of polyoxometalates (POMs) and their neutral alkoxy analogues [35] and heteropolyacids such as the Keggin cluster [36, 37]. 

The ample field of transition metal substituted polyoxometallates (POM), which are often other precursors for peroxo derivatives in catalytic processes, will be discussed in brief. 

Figure 6.22. The immobilization of polyoxometalate POM catalyst within a polyethyleneglycol layer.

Various Keggin-type polyoxometalates (POMs) were tested as catalysts for the ODS of gas oil with t-butyl hydroperoxide. Alumina-supported phosphomolybdic acid (H3PMoi2O40) proved to be quite active, yielding sulfur conversion higher than... 

Polyoxometalates (POMs), also known as heteropolyanions, are metal containing anions consisting of transition metal ions bonded to other ligands, mostly oxygen atoms, and generally, although not exclusively, based upon MoC>6 or WC>6 octahe-dra. While some POMs are polymeric, others appear as discrete entities. 

Polyoxometalates are important reagents in analytical chemistry and they also find applications in catalysis, molecular biology, materials sciences, and medicine. A recent study of nine Ndm polyoxometalates (POM) showed their aqueous 5 mM solutions to be weakly luminescent, whereas no luminescence at all is seen for the aquo ion. In particular, the bis(POM) complexes better protect the Ndm ion from nonradiative deactivations, for instance t(4F3/2) = 411 6nsfor[Nd(PWn039)2]11- and67 2 ns for [Nd(As4W4oOi4o)]25 (But et al., 2005). 

Few examples involve the use of dioxygen alone as the primary oxidant. The use of a Ru(III) ethylenediaminetetraacetate complex has been described [28] but this almost certainly involves a free-radical autoxidation pathway and offers no advantages. Following the initial report by Neumann et al. [29] on the use of [WZnRu2(0H)(H20)(ZnW9034)2]11 attention has been focused on the use of ruthenium-containing polyoxometalates (POMs) as catalysts for the aerobic... 

Polyoxometallates (POMs), molecular anionic metal oxides, show the ability to act as homogeneous photocatalysts in electron transfer from organic electron donors to metal ions. In the process, illumination at the LMCT band (visible and near-UV regions) renders POMs strong oxidants that are able to abstract electrons from a... 

Recently, Hill and coworkers [69] have developed a homogeneous Co catalyst that self-assembles in water from inorganic salts (Co, W, and P). It employs a polytungstate polyoxometalate (POM) ligand, which is oxidatively resistant, thus enhancing... 

Key Words P-31 solid-state NMR, 31P CP/MAS, Ultra-fast MAS, Phosphorylated amino acids, Nucleotides, Nucleic acids, Phosphate glasses, Aluminophosphates, Molecular sieves, Catalysts, Polyoxometalate (POM), Metal-organic framework (MOF), Inclusion complexes. 

Polyoxometalates (POMs), also known as heteropolyacids (HPA),3 are a class of compounds formed from negatively charged inorganic metal-oxygen building blocks. When charge-balanced with cationic species, POMs self-assemble into unusual 3D structures with specific topological and electronic properties.214 POMs are commonly formed from polyanions of early transition metals such as W, Mo or V. These anions can be substituted with other transition metals. The diversities in POMs composition and structure make them attractive for many applications, particularly as Bronsted acid and redox catalysts. For example,... 

In the literature (and here) the term "polyoxometalate" (POM) is used exchangeable with the term "heteropoly compounds" or heteropolyacids - abbreviated as HPA. 

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