title: Raman and ab initio studies of simple and binary 1-alkyl-3-methylimidazolium ionic liquids.
abstract: 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.
authors.affiliation: Department of Chemistry, Technical University, DK-2800 Lyngby, Denmark. rwb@kemi.dtu.dk
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Berg
authors.forename: Maggel
authors.initials: M
authors.lastname: Deetlefs
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Seddon
authors.forename: Irene
authors.initials: I
authors.lastname: Shim
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Thompson