Full Paper

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X-ray Photoelectron Spectroscopy and Theoretical Calculations

  1. Till Cremer1,
  2. Claudia Kolbeck1,
  3. Kevin R. J. Lovelock Dr.2,
  4. Natalia Paape3,
  5. René Wölfel3,
  6. Peter S. Schulz Dr.3,
  7. Peter Wasserscheid Prof. Dr.3,
  8. Henry Weber4,
  9. Jens Thar4,
  10. Barbara Kirchner Prof. Dr.4,
  11. Florian Maier Dr.1,
  12. Hans-Peter Steinrück Prof. Dr.1

Article first published online: 23 JUL 2010

DOI: 10.1002/chem.201001032

Issue

Chemistry - A European Journal

Chemistry - A European Journal

Volume 16, Issue 30, pages 9018–9033, August 9, 2010

Additional Information

How to Cite

Cremer, T., Kolbeck, C., Lovelock, Kevin R. J., Paape, N., Wölfel, R., Schulz, Peter S., Wasserscheid, P., Weber, H., Thar, J., Kirchner, B., Maier, F. and Steinrück, H.-P. (2010), Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X-ray Photoelectron Spectroscopy and Theoretical Calculations. Chem. Eur. J., 16: 9018–9033. doi: 10.1002/chem.201001032

Author Information

  1. 1

    Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen (Germany), Fax: (+49) 9131-85-28867

  2. 2

    School of Chemistry, The University of Nottingham, Nottingham, NG7 2RD (UK)

  3. 3

    Lehrstuhl für Chemische Reaktionstechnik, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen (Germany)

  4. 4

    Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstraße 2, 04103 Leipzig (Germany)

Publication History

  1. Issue published online: 30 JUL 2010
  2. Article first published online: 23 JUL 2010
  3. Manuscript Received: 20 APR 2010

Funded by

  • DFG

SEARCH

SEARCH BY CITATION

ARTICLE TOOLS

View Full Article with Supporting Information (HTML) Get PDF (921K)

Keywords:

  • charge transfer;
  • density functional calculations;
  • electronic interactions;
  • ionic liquids;
  • NMR spectroscopy;
  • X-ray photoelectron spectroscopy

Abstract

Ten [C8C1Im]+ (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl−, Br−, I−, [NO3]−, [BF4]−, [TfO]−, [PF6]−, [Tf2N]−, [Pf2N]−, and [FAP]− (TfO=trifluoromethylsulfonate, Tf2N=bis(trifluoromethylsulfonyl)imide, Pf2N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C8C1C1Im]+ (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br− and [Tf2N]− were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While 1H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C2 position and the anion, a comparative XPS study provides first direct experimental evidence for cation–anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid’s anion. These charge-transfer effects are found to be surprisingly similar for [C8C1Im]+ and [C8C1C1Im]+ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.

View Full Article with Supporting Information (HTML) Get PDF (921K)