Role of cation size in the energy of electron transfer to 1:1 polyoxometalate ion pairs {(M+)(Xn+VW11O40)}(8–n)–(M=Li, Na, K)

Abstract

The use of soluble salts of polyoxometalates (d0-early-transition metal oxygen-anion clusters or POMs) as selective oxidation or electron-transfer catalysts, as probes in physical-organic and biological chemistry, and in the study of electron-and energy-transfer phenomena constitutes a substantial and rapidly growing literature. While rarely addressed, however, POM solutions contain equilibrium distributions of free anions and ion-paired structures of variable stoichiometry. Thus, although studies of crystalline POM salts used in heterogeneous catalysis clearly indicate that cation-anioninteractions dramatically alter POM properties in these static ideal cases, the influence of ion pairing on POM reactions in solution is often ignored. Even in reports that document the influence (typically on reaction rates) of added cations, the relationship between observed effects and the properties of specific solution-POM Structures is left to conjecture. Partly to blame is the difficulty encountered in determining the extent and stoichiometry of ion-pair formation, a necessary prerequisite for assigning physical properties to specific olution-POM structures.

Citation

Grigoriev, Vladimir A.; Hill, Craig L.; Weinstock, Ira A. 2000. Role of cation size in the energy of electron transfer to 1:1 polyoxometalate ion pairs {(M+)(Xn+VW11O40)}(8–n)–(M=Li, Na, K). Journal of the American Chemical Society. Vol. 122, no. 14 (2000): Pages 3544-3545