Solvation effect of Li+ on the voltammetric properties of [PMo12O40]3-.: Part 2:: Comparative studies on the preferential solvation in acetonitrile plus S and acetone plus S mixtures

For [PMo12O40](3-), the presence of Li+ produced a two-electron wave at nearly the same potential as the first one-electron wave in acetonitrile or acetone. The voltammetric behavior of [PMo12O40](3-) in a binary mixture of acetonitrile and solvent S was compared with those in a mixture of acetone and S. When the donor number (DN) of S > 20, the first two-electron wave was converted into one-electron waves in such binary mixtures. The conversion occurred at lower mole fractions of S in an acetonitrile 4 S mixture than in an acetone + S mixture. The Li-7 NMR results showed that the preferential solvating ability of Li+ with S was greater in the former mixture. A linear relationship was found between the iso-solvation point x(iso)(S) and the reciprocal of the difference between the DNs of S and acetonitrile, which gave the basis to explain the anomalies observed for a mixture of acetonitrile and H2O.