The intrinsic anodic stability of several anions comprising solvent-free ionic liquids

Salts of the form 1,2-dimethyl-3-propylimidazolium X [where X = AsF6-, PF6-, (CF3SO2N-, and (CF3SO2C-] were prepared and purified. Linear sweep voltammetry was conducted at 80 degrees C, a temperature at which all four salts were molten, at Pt, W, and glassy carbon working electrodes. We found that the intrinsic anodic stability of these anions was in the order (CF3SO2C- > (CF3SO2N- similar to AsF6- > PF6-. These experimental solution-phase oxidation potentials correlated well with gas-phase highest occupied molecular orbital energies calculated by an ab initio technique.