Isoflurane as a solvent for electrochemistry. Electrooxidation study of icosahedral carborane anions in four different solvents

Voltammetric studies of icosahedral carborane anions CB11Me12- (1), 1-H-CB11Me11- (2), 1-H-12-H-CB11Me10- (3), and 1-H-12-I-CB11Me10- (4) are reported in isoflurane (1-chloro-2,2,2-trifluoroethyl difluoromethyl ether) and in three other solvents with different polarity (liquid SO2, acetonitrile, dichloromethane). They demonstrate the first use of isoflurane as a non-polar electrochemical solvent. The anions 1, 2 and 3 show reversible one-electron oxidations in all four solvents, whereas the oxidation of 4 is irreversible even at high scan rates. The measured half-wave potentials (E1/2) show a remarkable variation in the four different solvents. The E1/2 values are discussed in terms of specific solvation of the anions. The experimental results correlate fairly well with density functional theory (DFT) calculations.

► We report a new non-polar room temperature electrochemical solvent, isoflurane. ► We study elctrooxidation of carborane anions in solvents with high to low polarity. ► Icosahedral carboranes show one-electron reversible oxidation in various solvents. ► Variation of E1/2 values in various solvents are attributed to specific solvation. ► DFT calculations describe fairly well the E1/2 values with the solvent polarity.