Projects per year
The structure of the Keggin-type β-[PW12O40]3- (PW12) polyoxometalate, with n-Bu4N+ as the countercation, has been determined for the first time by single-crystal X-ray analysis and compared to data obtained from a new determination of the structure of the α-PW12 isomer, having the same countercation. Analysis of cyclic voltammograms obtained in CH3CN (0.1 M [n-Bu4N][PF6]) reveals that the reversible potential for the β-PW12 isomer always remains ca. 100 mV more positive than that of the α-PW12 isomer on addition of the acid CF3SO3H. Simulations of the cyclic voltammetry as a function of acid concentration over the range 0-5 mM mimic experimental data exceptionally well. These simulation-experiment comparisons provide access to reversible potentials and acidity constants associated with α and β fully oxidized and one- and two-electron reduced systems and also explain how the two well-resolved one-electron W(VI)/W(V) processes converge into a single two-electron process if sufficient acid is present. 183W NMR spectra of the oxidized forms of the PW12 isomers are acid dependent and in the case of β-PW12 imply that the bridging oxygens between the WI and WII units are preferentially protonated in acidic media. EPR data on frozen solutions of one-electron reduced β-[PWVWVI11O40]4- indicate that either the WI or the WIII unit in β-PW12 is reduced in the β-[PWVI12O40]3-/β-[PWVWVI11O40]4- process. In the absence of acid, reversible potentials obtained from the α- and β-isomers of PW12 and [SiW12O40]4- exhibit a linear relationship with solvent properties such as Lewis acidity, acceptor number, and polarity index.
- 1 Finished
Wallace, G., Forsyth, M., Macfarlane, D., Officer, D., Cook, M. J., Dodds, S., Spinks, G., Alici, G., Moulton, S., in het Panhuis, M., Kapsa, R. M. I., Higgins, M., Mozer, A., Crook, J., Innis, P., Coote, M. L., Wang, X., Howlett, P. C., Pringle, J. M., Hancock, L., Paull, B., Sparrow, R., Zhang, J., Spiccia, L., Diamond, D., Guldi, D., Kim, S. J., Unwin, P. & Watanabe, M.
30/06/14 → 30/06/21