SOLVATION IN IONIC LIQUIDS - AN EPR STUDY

EPR spectra of 2,2,6,6-tetramethylpiperidine-1-oxyl (tempo) and of 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (tempamine) were obtained in ionic liquids composed of 1-ethyl-3-methylimidazolium chloride, ImCl, and aluminium chloride and in mineral oil. In basic solutions, those containing a molar excess of ImCl, the rotational correlation time of tempamine was ca. 27 times longer than for tempo. This is probably the result of a specific interaction of melt species with the basic NH2 moiety of tempamine. The N-14 hyperfine isotropic coupling constants of tempo, 16.0 G, and tempamine, 15.8 G, in basic solution are comparable to those in DMSO and DMF. In acidic solution the N-14 hyperfine coupling constant of tempo, 20.5 G, is appreciably larger due to adduct formation with AlCl3.