Macroelectrode voltammetry in toluene using a phosphonium–phosphate ionic liquid as the supporting electrolyte

The ability of the ionic liquid trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate (aph4.cph12) to act as an ionic conductor in toluene has been investigated at platinum and glassy carbon macrodisc electrodes. Ionic liquid concentrations of 0.1–0.4 M provide close to ideal conditions for transient dc cyclic and ac voltammetric techniques. A potential window of almost 5 V is available at a glassy carbon electrode (the neat ionic liquid has a potential window of approximately 6 V). In the presence of 0.4 M ionic liquid, uncompensated solution resistances (in the range of 3–4 kΩ) are of the same order of magnitude as encountered in commonly used non-aqueous electrochemical solvents such as dichloromethane containing 0.1M Bu4NPF6 as the electrolyte. Voltammetric data on ferrocene, the cobaltocenium cation, [Ru(bipy)3]2+ and C60 in toluene containing aph4.cph12 demonstrate the advantages of using this ionic liquid as an electrolyte in highly resistive media.