The peculiar nature of molecular interactions between an imidazolium ionic liquid and acetone

Johannes Kiefer, Marta Martinez Molina, Kristina Noack

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)


We present novel insights into the molecular interactions between polar solvents and imidazolium ionic liquids using the example of 1-ethyl-3-methylimidazolium ethyl sulfate and acetone. Recently published volumetric property data of this particular system have revealed peculiarities which could not be fully explained by steric effects. In order to shed light on the behavior at a molecular level, we apply IR spectroscopy and analyze solvent-induced line shifts as well as the excess IR spectra. From the spectroscopic results a conclusive picture of the site-specific molecular interactions is developed and our explanation is in concert with the volumetric effects. The data suggest the initial formation of trimers in which acetone interacts with existing ion pairs through interactions of the acetone oxygen atom with the imidazolium ring rather than forming directed hydrogen bonds at the CH moieties. With further addition of acetone, tetramers are formed which significantly weaken the interionic interactions and eventually initiate ion pair dissociation. Once the ions are released, the anion is rapidly saturated with acetone while the cation solvation proceeds more slowly with acetone addition.
Original languageEnglish
Pages (from-to)1213-1220
Number of pages8
Issue number5
Early online date16 Feb 2012
Publication statusPublished - 10 Apr 2012


  • hydrogen bonds
  • ion pairs
  • ionic liquids
  • IR spectroscopy
  • solvent effects


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