Vibrational signatures of anionic cyano groups in imidazolium ionic liquids

Johannes Kiefer*, Kristina Noack, Tatiana C. Penna, Mauro C. C. Ribeiro, Henry Weber, Barbara Kirchner

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The vibrational spectra of two cyano-based ionic liquids, 1-ethyl-3-methylimidazolium dicyanamide (C(2)C(1)Im DCA) and 1-ethyl-3-methylimidazolium tricyanomethanide (C(2)C(1)Im TCM) are revisited experimentally and computationally using IR spectroscopy and ab initio molecular dynamics simulations, respectively. In the experimental spectrum of C(2)C(1)Im DCA, a number of interesting vibrational signatures are found. Aside from the expected symmetric and anti-symmetric stretching bands of the cyano groups, a Fermi resonance of a combination band and a CN stretching normal mode is identified. The assignment is confirmed by a normal mode analysis of the AIMD based IR spectrum. The AIMD does not only predict the existence of the combination band but also seems to capture the frequency shift and intensity change caused by Fermi resonance. The interpretation of the experimental C(2)C(1)Im TCM spectrum is more straightforward as no resonance effects are found. The combination of experimental spectroscopy and advanced AIMD simulations is a very promising approach to gain new insights into the behavior of room-temperature ionic liquids. (C) 2016 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)141-146
Number of pages6
JournalVibrational spectroscopy
Volume91
Early online date27 May 2016
DOIs
Publication statusPublished - Jul 2017

Keywords

  • FTIR
  • Ionic liquid
  • Molten salt
  • Fermi resonance
  • 1-ETHYL-3-METHYLIMIDAZOLIUM ETHYL SULFATE
  • DENSITY-FUNCTIONAL THEORY
  • CH STRETCHING VIBRATIONS
  • AB-INITIO
  • CONFORMATIONAL ISOMERISM
  • MOLECULAR-DYNAMICS
  • INFRARED-SPECTROSCOPY
  • CRYSTAL-STRUCTURE
  • RATIONAL DESIGN
  • HYDROGEN-BONDS

Cite this

Kiefer, J., Noack, K., Penna, T. C., Ribeiro, M. C. C., Weber, H., & Kirchner, B. (2017). Vibrational signatures of anionic cyano groups in imidazolium ionic liquids. Vibrational spectroscopy, 91, 141-146. https://doi.org/10.1016/j.vibspec.2016.05.004