title: Mass spectrometric studies of 1-ethyl-3-methylimidazolium and 1-propyl-2,3-dimethylimidazolium bis(trifluoromethyl)-sulfonylimides.
abstract: BACKGROUND
  Ionic liquids ([Cat(+)][An(-)]) were believed to decompose before reaching vaporization temperatures, but recently some of them have been shown to vaporize congruently. Low-temperature vaporization of ionic substances is an intriguing phenomenon, so the vapor-phase composition and reactions of ionic liquids deserve more extensive study.
  
  
  METHODS
  Evaporation of two ionic liquids, [C2MIM(+)][Tf2 N(-)] and [C3MMIM(+)][Tf2N(-)], was studied by means of Knudsen effusion mass spectrometry. These liquids were also characterized using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, UV/Vis, IR, NMR spectroscopy, and elemental analysis.
  
  
  RESULTS
  The vaporization enthalpies of (118 ± 3) and (124 ± 2) kJ·mol(-1) were determined for [C2MIM(+)][Tf2N(-)] and [C3MMIM(+)][Tf2N(-)], respectively. The corresponding equations for their saturated vapor pressures are: ln(p{[C2MIM(+)][Tf2N(-)]}/Pa) = -(14213 ± 325)/(T/K) + (26.57 ± 1.04), ln(p{[C2MMIM(+)][Tf2N(-)]}/Pa) = -(14868 ± 221)/(T/K) + (27.19 ± 0.60). The MALDI studies (positive and negative ion modes) enabled detection of monomeric [Cat(+)] and [An(-)] ions, the cluster ions {[Cat(+)]2 [An(-)]}(+) and {[Cat(+)][An(-)]2}(-), and some complex anions {2[An(-)] + Na(+)}(-), {2[An(-)] + K(+)}(-), {2[An(-)] + Cu(+)}(-) and {3[An(-)] + Ca(2+)}(-).
  
  
  CONCLUSIONS
  Knudsen effusion mass spectrometry proved to be a valuable method to study the thermodynamics of ionic liquids. The saturated vapor pressure and vaporization enthalpy of [C3MMIM(+)][Tf2N(-)] were accurately determined for the first time. MALDI is also capable of providing indirect information on hydrogen bonding.
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Norbert S
authors.initials: NS
authors.lastname: Chilingarov
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Artem A
authors.initials: AA
authors.lastname: Medvedev
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Grigoriy S
authors.initials: GS
authors.lastname: Deyko
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.|N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninskiy Avenue 47, 119991, Moscow, Russia.
authors.forename: Leonid M
authors.initials: LM
authors.lastname: Kustov
authors.affiliation: N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninskiy Avenue 47, 119991, Moscow, Russia.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Chernikova
authors.affiliation: N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninskiy Avenue 47, 119991, Moscow, Russia.
authors.forename: Lev M
authors.initials: LM
authors.lastname: Glukhov
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Vitaliy Yu
authors.initials: VY
authors.lastname: Markov
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Il'ya N
authors.initials: IN
authors.lastname: Ioffe
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Senyavin
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Marina V
authors.initials: MV
authors.lastname: Polyakova
authors.affiliation: Chemistry Department, M. V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia.
authors.forename: Lev N
authors.initials: LN
authors.lastname: Sidorov