Solvation of α-hydroxydiphenylmethyl radical in room temperature ionic liquids studied by transient FT-EPR spectroscopy

To understand solvation in room temperature ionic liquids (RTILs), an FT-EPR spectrum of α-hydroxydiphenylmethyl (HDPM) radical was measured in several RTILs of tert-alkylammonium or alkylimidazolium salts with anions of PF 6 - , BF 4 - , (CF3SO2)2N−, CF 3 SO 3 - , WO 4 2 - , Cl− and Br−. The hyperfine coupling constant of the hydroxyl proton depends on Gutmann’s donor number of the anions, while the constants of phenyl α-protons are essentially the same for these RTILs. This result suggests the electron donor character of anions is important in HDPM solvation in RTILs through the anion-OH group hydrogen-bond.