The probe dependence of solvation dynamics and rotation in the ionic liquid 1-butyl-3-methyl-imidazolium hexafluorophosphate

Solvation and rotational dynamics were measured using several solvatochromic probes in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim ⁺][PF ₆ ^-]) to determine the sensitivity of these dynamics to the choice of probe. In all solutes an unresolved ultrafast component (<5 ps) and highly non-exponential solvation dynamics were observed, consistent with results of prior studies in imidazolium ionic liquids. Solvation times varied by a factor of ∼2 among the probes studied. Rotational correlation functions were generally non-exponential, but in all cases rotation times track solvent viscosity in the same manner as in conventional solvents.