University of Oulu

Ivar Kuusik, Mati Kook, Rainer Pärna, Antti Kivimäki, Tanel Käämbre, Liis Reisberg, Arvo Kikas, Vambola Kisand, The electronic structure of ionic liquids based on the TFSI anion: A gas phase UPS and DFT study, Journal of Molecular Liquids, Volume 294, 2019, 111580, ISSN 0167-7322,

The electronic structure of ionic liquids based on the TFSI anion : a gas phase UPS and DFT study

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Author: Kuusik, Ivar1; Kook, Mati1; Pärna, Rainer1,2;
Organizations: 1Institute of Physics, University of Tartu, W. Ostwaldi 1, EE-50411 Tartu, Estonia
2MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund, Sweden
3Nano and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.5 MB)
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Language: English
Published: Elsevier, 2019
Publish Date: 2021-08-17


The valence bands of [EMIM][TFSI], [DEME][TFSI] and [PYR1,4][TFSI] gas-phase ion pairs have been investigated using ultraviolet photoelectron spectroscopy (UPS). The photoelectron spectra are interpreted by using several density functional and ab initio calculation methods. Although the experimental vapor phase spectra are similar, the different calculation methods make different predictions about the HOMO molecular state of the ion-pairs of the ionic liquids. The HOMO state of the [DEME][TFSI] ion-pair is due to the TFSI anion, while in [EMIM][TFSI] it is due to the EMIM cation. However, it is difficult to make conclusive assignments for the [PYR1,4][TFSI] ionic liquid. All calculation methods predict the LUMO to be of cationic origin in all the studied ion-pairs.

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Series: Journal of molecular liquids
ISSN: 0167-7322
ISSN-E: 1873-3166
ISSN-L: 0167-7322
Volume: 294
Article number: 111580
DOI: 10.1016/j.molliq.2019.111580
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Funding: The authors gratefully acknowledge the financial support by the Estonian Research Council (IUT2-25) and the Estonian Centre of Excellence in Research project “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (2014-2020.4.01.15-0011). The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.
Copyright information: © 2019 Elsevier B.V. All rights reserved.