title: Ion-pair formation in the ionic liquid 1-ethyl-3-methylimidazolium bis(triflyl)imide as a function of temperature and concentration.
abstract: The structures and ion-pair formation in the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are studied by a combination of FTIR measurements and DFT calculations. We could clearly distinguish imidazolium cations that are completely H-bonded to anions from those that are single H-bonded in ion pairs. Ion-pair formation already occurs in the neat IL and rises with temperature. Ion-pair formation is strongly promoted by dilution of the IL in chloroform. In these weakly polar environments ion pairs H-bonded via C(2)H are strongly favored over those H-bonded via C(4,5)H. This finding is in agreement with DFT (gas phase) calculations, which show a preference for ion pairs H-bonded via C(2)H as a result of the acidic C(2)H bond.
authors.affiliation: Institut für Chemie, Abteilung Physikalische Chemie Universität Rostock, 18051 Rostock, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Köddermann
authors.forename: Christiane
authors.initials: C
authors.lastname: Wertz
authors.forename: Andreas
authors.initials: A
authors.lastname: Heintz
authors.forename: Ralf
authors.initials: R
authors.lastname: Ludwig