Dawson ions

The Dawson structure, C, can be visualized as being formed by removing the three basal octahedra from each of two a-Keggin ions which are then fused together. By omitting the four octahedra at the front, the oxygens associated with the 2 heteroatoms can be seen more clearly (D). 

Bioinorganic applications of m.c.d. spectroscopy copper, rare earth ions, cobalt and non-heme iron systems. D. M. Dooley and J. H. Dawson, Coord. Chem. Rev., 1984, 60,1 (176). 

Allen GC, Warren KD (1974) The Electronic Spectra of the Hexafluoro Complexes of the Second and Third Transition Series. 19 105-165 Alonso JA, Baibas LC (1993) Hardness of Metallic Clusters. 80 229-258 Alonso JA, Baibas LC (1987) Simple Density Functional Theory of the Electronegativity and Other Related Properties of Atoms and Ions. 66 41-78 Andersson LA, Dawson JH (1991) EXAFS Spectroscopy of Heme-Containing Oxygenases and Peroxidases. 74 1-40 Antanaitis BC, see Doi K (1988) 70 1-26... 

Meares, P. (Ed.), Membrane Separation Processes, Elsevier, Amsterdam, 1976. Meares, P., J. F. Thain, and D. G. Dawson, Transport across ion-exchange membranes The frictional model of transport, in Membranes—A Series of Advances (Ed. G. Eisenman), Vol. 1, p. 55, M. Dekker, New York, 1972. Schlogl, R., see page 415. 

Matsumiya etal. 91) determined zinc in both serum and urine by direct dilution. Dawson and Walker92) diluted plasma 20-fold with 0.1 AT hydrochloric acid, in whole blood diluted 100-fold, and in urine diluted 10-fold. Suppression of up to 15 % of the absorbance by inorganic components was overcome by adding the appropriate amounts of those ions to the standards. Willis93) determined zinc in urine by direct aspiration. Other workers have also determined zinc in urine 79>94) and in blood and urine 9S). 

Dawson, P.H. Whetten, N.R. Nonlinear Resonances in Quadrupole Mass Spectrometers Due to Imperfect Fields. II. Quadrupole Mass Filter and die Monopole Mass Spectrometer. Int. J. Mass Spectrom. Ion Phys. 1969, 5, 1-12. 

A. A. Noyes 5 to the belief that the number of molecules in the soln. is not changed by the addition of more iodine because polyiodides are formed MI+mI2=MI2 +i. Y. Osaka showed that the rise of the f.p. which occurs when iodine is added to hydriodic acid or to aq. soln. of potassium iodide is proportional to the amount of iodine added, and is greater for hydriodic acid than for the potassium salt. Hence, the total concentration of the ions and of unionized molecules is decreased by the addition of iodine. A. A. Jakowkin inferred from the partition coeff. of iodine in dil. soln. that potassium tri-iodide was formed, and that with more cone. soln. still more complex polyiodides are produced. Still further, the change in the partition coeff. of iodine between aq. soln. of potassium iodide and nitrobenzene led H. M. Dawson and R. Gawler to infer that polyiodides as high as potassium ennea-iodide, KI9, are probably present in soln., although no such compound has been obtained in the solid state. H. L. Wells and H. L. Wheeler and others, however, have prepared several solid alkali polyiodides for example ... 

The electrochemistry of heteropolymolybdates parallels that of the tungstates but with the following differences the reduction potentials are more positive and the primed species (metal-metal bonded ) are much less stable. Scheme 7 applies for or-fSiMo O ]4-. Species in parentheses are detectable only by rapid scan cyclic voltammetry, and XVIII decomposes rapidly at 0°C. The reduced anions such as II and IV are easily obtained by controlled potential electrolysis or by careful chemical reduction, e.g. with ascorbate. The use of metal ion reductants generally leads to other reactions, (equation 7). The reduced anions slowly isomerize (equation 8). The isomerization can be followed polarographically (all S potentials are more positive) or by NMR spectroscopy. By this means / isomers of most Keggin and Dawson molybdates have been prepared. 

Oxyanions of sufficient basicity will catalyze the hydrolysis of all but the least reactive esters but since the latter include the esters of the common aliphatic alcohols, early attempts to detect the reaction were negative or inconclusive. Dawson and Lowson274, claimed to have detected catalysis by acetate ion of the hydrolysis of ethyl acetate as early as 1927, but the extent of catalysis observed was too small to rule out the possibility that salt or solvent effects were, in fact, responsible. 

M3Oi3 groups. H6As2Mo,8062 and S2Moi8062 have also been synthesized (2, 31). A complex containing F ions, F F NaWigO (32), is isostructural with the Dawson species, P2W 8062. ... 

Heteropolyacids are prepared in solution by acidifying and heating in the appropriate pH range (], 49-54). For example, 12-tungstophosphate is formed according to Eq. (1). Free acids are synthesized primarily by the following two methods (1) by extraction with ether from acidified aqueous solutions and (2) by ion exchange from salts of heteropolyacids. Dawson-type heteropolyanions,... 

Lacunary spedes can act as structural motifs with numerous metal cations, leading to mono-, di- and trinuclear transition-metal-substituted POMs according to the number of vacant sites. The metal incorporation involves the reaction of aquated first-row and occasionally second-row d-block metal ions, M(H20)6z +, with a lacunary POM derived from the Keggin, Wells-Dawson and other POM families. In addition, lacunary spedes assemble into large POM structures, either directly or with incorporation of metal ion linkers. 

In our attempts to design functional clusters we have focused on substitution of the heteroanions within the Wells-Dawson structure to create nonconventional Dawson clusters incorporating two pyramidal anions. Our design rationale was based on the idea that such clusters may exhibit unprecedented properties arising from the intramolecular electronic interactions between the encapsulated anions (in this case we aimed to engineer between S S atoms of two encapsulated sulfite ions), thus providing a novel route to manipulate the physical properties of... 

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