Voltammetric Studies of Proton Reduction in 1-Butyl-1-Methylpyrrolidinium Trifluoromethanesulfonate

The reduction of trifluoromethanesulfonic acid (triflic acid) in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate (BMPY TfO) has been investigated at platinum. In the concentration range 7 mM to 55 mM, triflic acid undergoes a broad reduction process at -0.25V vs Ag/AgCl at 100 mV/s, followed by a narrower oxidation process at +0.40V. Addition of water results in shifts of these potentials to more central values, with closer peak spacing (340 mV) at the 4.00 : 1.00 mole ratio H2O : triflic acid point. These results suggest that the proton is associated via a three-center bond with two triflate anions in the BMPY TfO / triflic acid solution. Addition of water leads to complexation of the proton by water molecules, with a resulting potential shift for the redox processes.