Dawson polyoxometalates

The formation of sandwich-type POMs from solutions of metal cations and triva-cant heteropolytungstate species may alternatively be viewed as means to sequester cations from solution [116]. The question then arises if reversible dissociation of the metal cations from the multidentate ligands is possible as well. The sequestration and subsequent release of metal cations under appropriate conditions is of considerable interest in waste decontamination technology as well as in medicine [124]. Following these ideas, the demetallation process of ten multi-iron Wells-Dawson polyoxometalates is studied by cyclic... 

Table 10 Isomers of Wells-Dawson polyoxometalates, [X2Mi8062] ...

Cannizzo, C., Mayer, C., Secheresse, R, et al. (2005). Covalent Hybrid Materials Based on Nanolatex Particles and Dawson Polyoxometalates, Adv. Mater., 17, pp. 2888-2892. 

Structural and Electronic Features of Wells-Dawson Polyoxometalates... 

E° values of several other Dawson-type V-substituted polyoxometalates can be found in Ref. 35 and the citations therein. Selected equilibria ... 

In one such approach we seek to exploit the potential signal transduction properties of the thermochromic Dawson [40] polyoxometalates and combine this with a fluorescent POM-hybrid to produce a device that could respond optically as a function of the local environment, see Figure 2.12. In this example, the clusters would be positioned on a gold surface using SAMs (Self-assembled monolayer) with a cationic tail and local positional control could be aimed using self-assembly, or even by means of an atomic force microscope tip. 

Figure 5.24 The two-dimensional layer structure of [Ln2(H20)9(a2-P2 Vi706i)]" [36]. (Reprinted with permission fromY. Lu, etal., New polyoxometalate compounds built up of lacunary Wells-Dawson anions and trivalent lanthanide cations, Inorganic Chemistry, 45, no. 5, 2055-2060 (Figure 3), 2006. 2006 American Chemical Society.)...

Figure 14.1 Types of polyoxometallates formed by different arrangements of MOs octahedra. (a) Lindqvist, (b) Anderson, (c) Keggin, (d) Dawson.

The reducibility of type-I polyoxometalates, notably the Keggin, Wells-Dawson, and Lindqvist (hexametalate) structures, to mixed-valence heteropoly blues was well established in the 1960s and... 

S. Uchida, R. Kawamoto, T. Akatsuka, S. Hikichi, N. Mizuno, Structures and sorption properties of ionic crystals of macrocation-Dawson-type polyoxometalates with different charges, Chem. Mater. 17 (2005) 1367. 

I-P2W17O61] " and [a-2-P2Wi706i], isomers of the monovacant Wells-Dawson anion, and [a-B-PW9034] as building blocks to new lanthanide polyoxometalate materials. 

Polyoxometalate anions, due to the large number of oxygen atoms, have also been used to control the hydrolysis of the oxophilic lanthanide ions (Pope, 2008). Hydrolysis of Y(III) or Yb(III) by carbonate in the presence of the trivacant Wells-Dawson polyoxoanion, a-[P2Wi505g] produced... 

Polyoxometalate Chemistry for Nano-Composite Design, [Symposium], Honolulu, HI, United States, Dec. 17-19, 2000, ed. T. Yamase and M.T. Pope, Kluwer Academic/Plenum Publishers, New York, N.Y., 2002 R 278 D.C. Crans, H.S. Bedi, S. Li, B. Zhang, K. Nomiya, N.C. Kasuga, Y. Nemoto, K. Nomura, K. Hashino, Y. Sakai, Y. Tekeste, G. Sebel, L.-A.E. Minasi, J.J. Smee and G.R. Willsky, Tetravanadate, Decavanadate, Keg-gin and Dawson Oxotungstates Inhibit Growth of S. Cerevisiae , p. 181... 

Polyoxometalate compounds comprise polyoxometalate anions, the structure of which are based on a plurality of condensed metal-oxide species. With protons as counter-ions, they exhibit Bronsted acidity. There are a number of known polyoxometalate structiues, for example the Wells-Dawson, Anderson and Keggin forms (39). 

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