Correlation between Soft X-ray Absorption and Emission Spectra of the Nitrogen Atoms within Imidazolium-Based Ionic Liquids

Research output: Contribution to journalArticle

Abstract

Soft X-ray absorption spectroscopy (XAS) has been performed on the N K-edge of two imidazolium-based ionic liquids (ILs), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C 2 mim][TFSA]) and 1-ethyl-3-methylimidazolium bromide ([C 2 mim][Br]), to clarify the electronic structures of the ILs. Soft X-ray emission spectroscopy (XES) has also been applied to the ILs by excitation at various X-ray energies according to the XAS spectra. It was possible to fully associate the XAS peaks with the XES peaks. Additionally, both XAS and XES spectra of the ILs were well reproduced by the theoretical spectra for a single-molecule model on [C 2 mim] + and [TFSA] - using density functional theory. The assignments for the XAS and XES peaks of the ILs were accomplished from both experimental and theoretical approaches. The theoretical XAS and XES spectra of [C 2 mim] + and [TFSA] - did not significantly depend on the conformations of the ions. The reproducibility of the theoretical spectra for the single-molecule model suggested that the interactions between the cations and anions are very weak in the ILs, thus scarcely influencing the electronic structures of the nitrogen atoms.

Details

Authors
External organisations
  • Yamaguchi University
  • RIKEN SPring-8 center
  • Hiroshima University
  • Saga University
Original languageEnglish
Pages (from-to)7480-7487
Number of pages8
JournalJournal of Physical Chemistry B
Volume120
Issue number30
Publication statusPublished - 2016 Aug 4
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes