Molecular Structure and Interactions in the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(Trifluoromethylsulfonyl)imide

Nilesh R. Dhumal, Kristina Noack, Johannes Kiefer, Hyung J. Kim*

*Corresponding author for this work

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

Electronic structure theory (density functional and Moller-Plesset perturbation theory) and vibrational spectroscopy (FT-IR and Raman) are employed to study molecular interactions in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Different conformers of a cation-anion pair based on their molecular interactions are simulated in the gas phase and in a dielectric continuum solvent environment. Although the ordering of conformers in energy varies with theoretical methods, their predictions for three lowest energy conformers in the gas phase are similar. Strong C-H center dot center dot center dot N interactions between the acidic hydrogen atom of the cation imidazole ring and the nitrogen atom of the anion are predicted for either the lowest or second lowest energy conformer. In a continuum solvent, different theoretical methods yield the same ion-pair conformation for the lowest energy state. In both phases, the method predicts that the anion is in a trans conformation in the lowest energy ion pair state. The theoretical results are compared with experimental observations from Raman scattering and IR absorption spectroscopies and manifestations of the molecular interactions in the vibrational spectra are discussed. The directions of the frequency shifts of the characteristic vibrations relative to the free anion and cation are explained by calculating the difference electron density coupled with electron density topography.

Original languageEnglish
Pages (from-to)2547-2557
Number of pages11
JournalJournal of Physical Chemistry A
Volume118
Issue number13
Early online date10 Mar 2014
DOIs
Publication statusPublished - 3 Apr 2014

Keywords

  • electron-transfer reactions
  • temperature molten-salts
  • ab-initio
  • quadropolar solvents
  • hydrogen-bonds
  • gas-phase
  • conformational equilibrium
  • dynamics
  • raman
  • solvation

Cite this

Molecular Structure and Interactions in the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(Trifluoromethylsulfonyl)imide. / Dhumal, Nilesh R.; Noack, Kristina; Kiefer, Johannes; Kim, Hyung J.

In: Journal of Physical Chemistry A, Vol. 118, No. 13, 03.04.2014, p. 2547-2557.

Research output: Contribution to journalArticle

Dhumal, Nilesh R. ; Noack, Kristina ; Kiefer, Johannes ; Kim, Hyung J. / Molecular Structure and Interactions in the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(Trifluoromethylsulfonyl)imide. In: Journal of Physical Chemistry A. 2014 ; Vol. 118, No. 13. pp. 2547-2557.
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abstract = "Electronic structure theory (density functional and Moller-Plesset perturbation theory) and vibrational spectroscopy (FT-IR and Raman) are employed to study molecular interactions in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Different conformers of a cation-anion pair based on their molecular interactions are simulated in the gas phase and in a dielectric continuum solvent environment. Although the ordering of conformers in energy varies with theoretical methods, their predictions for three lowest energy conformers in the gas phase are similar. Strong C-H center dot center dot center dot N interactions between the acidic hydrogen atom of the cation imidazole ring and the nitrogen atom of the anion are predicted for either the lowest or second lowest energy conformer. In a continuum solvent, different theoretical methods yield the same ion-pair conformation for the lowest energy state. In both phases, the method predicts that the anion is in a trans conformation in the lowest energy ion pair state. The theoretical results are compared with experimental observations from Raman scattering and IR absorption spectroscopies and manifestations of the molecular interactions in the vibrational spectra are discussed. The directions of the frequency shifts of the characteristic vibrations relative to the free anion and cation are explained by calculating the difference electron density coupled with electron density topography.",
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