Raman and ab initio studies of simple and binary 1-alkyl-3-methylimidazolium ionic liquids.
Raman spectra of the ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 1-hexyl-3-methylimidazolium chloride ([C6mim]Cl), and 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]), and binary mixtures thereof, have been assigned using ab initio MP2 calculations. The previously reported anti and gauche forms of the [C4mim]+ cation have been observed, and this study reveals this to be a general feature of the long-chain 1-alkyl derivatives. Analysis of mixtures of [C6mim]Cl and [C6mim][PF6] has provided information on the nature of the hydrogen bonding between the imidazolium headgroup and the anions, and the invariance of the essentially 50:50 mixture of the predominant conformers informs on the nature of glass formation in these systems.
Berg
Rolf W
RW
Department of Chemistry, Technical University, DK-2800 Lyngby, Denmark. rwb@kemi.dtu.dk
Deetlefs
Maggel
M
Seddon
Kenneth R
KR
Shim
Irene
I
Thompson
Jillian M
JM