Effects of functional group substitution on electron spectra and solvation dynamics in a family of ionic liquids

Ionic liquids containing ether-, alcohol- and alkyl-functionalized quaternary ammonium dications were studied by pulse radiolysis. Spectra on nanosecond timescales revealed that solvation of the excess electron is particularly slow in the case of the alcohol-derivatized ionic liquids. The blue shift of the electron spectrum to the customary 650 nm peak takes 25-40 ns at 21 °C. Comparison with the relaxation dynamics observed in viscous 1,2,6-trihydroxyhexane reveals the hindering effect of the ionic liquid lattice on hydroxypropyl side chain reorientation.