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

Voltammetric studies of icosahedral carborane anions CB 11 Me 12 - (1), 1 -H- CB 11 Me 11 - (2), 1 -H- 12 -H- CB 11 Me 10 - (3), and 1 -H- 12 -I- CB 11 Me 10 - (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.