Metal phosphates and phosphonates

Group (IV) metal phosphates and phosphonates, transition metal oxides (titanates, silicates, niobates, etc.), layered oxides, and double hydroxides (aluminum, magnesium, iron, etc.) are some of the inorganic compounds used as layered host ma-... 

Recently developed techniques for the fabrication of thin-film metal phosphates and phosphonates provide another method for the preparation of layered solids at surfaces. Layers of precisely controlled thickness can be built up by alternate immersion of a suitably pretreated surface in aqueous solutions of a soluble phosphate or phosphonate followed by an appropriate metal salt. This leads to the sequential build-up of thin metal containing films at the surface [72, 214] (see figure 6.18). The method is quite flexible and can be used to build up mixed microporous films on the surface which show molecular sieving properties [215, 216]. This building up approach looks very attractive for the systematic development of thin, selective films. 

Metal phosphates and phosphonates Zr(RP03)2, Zr(R0P03)2 (R = Ph, Me, Ft, CH2COOH) Negative 295... 

G. Alberti, R. Vivani, F. Marmottini, P. Zappelli, P, Microporous solids based on pillared metal(IV) phosphates and phosphonates , J. Porous Mater. 1998, 5, 205-220. 

Zinc [37], manganese [38], molybdenum [34], and vanadium [40,41] also form lamellar structures. For example, molybdenyl phenylphosphonate forms a linear structure with double chains in which the molybdenyl oxygens of the adjacent chains point toward each other and the phenyl groups are on the outside [42], As is the case with zirconium phosphate and phosphonate, the layered nature of the above metal phosphonates is similar to that of the respective phosphates. Among these, vanadium phosphonates have generated greater interest in view of their importance as industrial catalysts. 

The dependence of the activity of calcineurin on the redox state of the metal center highlights its importance for catalysis and provides clues to its function in that process. Site-directed mutagenesis studies of PPl, calcineurin, and bacteriophage X protein phosphatase have also provided insights regarding the roles of non-ligand active site residues. Furthermore, the contributions afforded by studies of synthetic model compounds which mimic features of metallophosphatase active sites provide important clues to possible catalytic mechanisms. Indeed many of these models exhibit impressive rate enhancements for phosphate and phosphonate ester hydrolysis [54-62]. In this section we discuss current models regarding the mechanism of phosphate ester hydrolysis by calcineurin and other metallophosphatases in consideration of these studies. 

Intercalation in Metal Phosphates, Hydrogen Phosphates, and Phosphonates... 

Recent work has shown that simple nonlabile mono-aqua metal complexes function as general base catalysts in the hydrolysis of neutral phosphate and phosphonate esters in aqueous solution. If general base catalysis operates the reaction of [Co(NH3)50H] with 4-nitrophenyldiethyl phosphate, then (1 = PNPDEP) will give free diethylphosphonic acid in solution, while direct nucleophilic displacement will give the (diethylphosphate)cobalt(III) cation (2). 

Phosphates and phosphonates of tetravalent metals as protonic conductors... 

Figure 2 Examples of molecules that have been used to produce self-assembled monolayers on various surfaces, a) Thiols have been used extensively to functionalize gold, silver, and other metals . b) Trichloro- and trialkoxy silanes are used to functionalize many oxide surfaces and are used industrially as adhesion promoters, c) Phosphates and phosphonates and d) catechols have been used to functionalize a number of transition metal oxides.

To date, the best-studied SAM system has been that of self-assembled alkanethiolates on gold, where thiols adsorb onto the gold surface in an initial lying-down phase followed by rearrangement into a standing-up phase, which completes the monolayer and results in highly ordered, two-dimensional structures. Alkyl phosphates and phosphonates constitute two further systems that have been shown to form ordered SAMs on metal oxide surfaces. - Transition metal oxides such... 

Depending on the final purpose of the material, the appropriate pillar can be chosen. This flexibifity in the PILC synthesis is one of the main advantages compared to other porous substrates, such as zeofites, which have one definite pore size. The technique not only focuses on clays, but other layered structures serve as host materials as well. Examples are layered double hydroxides (anionic clays), metal(IV)- phosphates and phosphonates,layered silicic acids, etc. [4,5]. 

Molecular phosphonate cages with metal, P, and O atoms as model compounds and a source for phosphate materials 99ACR117. 

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