Surface enrichment in equimolar mixtures of non-functionalized and functionalized imidazolium-based ionic liquids

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Title: Surface enrichment in equimolar mixtures of non-functionalized and functionalized imidazolium-based ionic liquids
Author(s): Heller, BSJ
Kolbeck, C
Niedermaier, I
Dommer, S
Schatz, J
Hunt, P
Maier, F
Steinrueck, H-P
Item Type: Journal Article
Abstract: For equimolar mixtures of ionic liquids with imidazolium‐based cations of very different electronic structure, we observe very pronounced surface enrichment effects by angle‐resolved X‐ray photoelectron spectroscopy (XPS). For a mixture with the same anion, that is, 1‐methyl‐3‐octylimidazolium hexafluorophosphate+1,3‐di(methoxy)imidazolium hexafluorophosphate ([C8C1Im][PF6]+[(MeO)2Im][PF6]), we find a strong enrichment of the octyl chain‐containing [C8C1Im]+ cation and a corresponding depletion of the [(MeO)2Im]+ cation in the topmost layer. For a mixture with different cations and anions, that is, [C8C1Im][Tf2N]+[(MeO)2Im][PF6], we find both surface enrichment of the [C8C1Im]+ cation and the [Tf2N]− (bis[(trifluoromethyl)sulfonyl]imide) anion, while [(MeO)2Im]+ and [PF6]− are depleted from the surface. We propose that the observed behavior in these mixtures is due to a lowering of the surface tension by the enriched components. Interestingly, we observe pronounced differences in the chemical shifts of the imidazolium ring signals of the [(MeO)2Im]+ cations as compared to the non‐functionalized cations. Calculations of the electronic structure and the intramolecular partial charge distribution of the cations contribute to interpreting these shifts for the two different cations.
Publication Date: 17-Jul-2018
Date of Acceptance: 3-Apr-2018
URI: http://hdl.handle.net/10044/1/65386
DOI: https://dx.doi.org/10.1002/cphc.201800216
ISSN: 1439-7641
Publisher: Wiley
Start Page: 1733
End Page: 1745
Journal / Book Title: ChemPhysChem
Volume: 19
Issue: 14
Copyright Statement: © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Keywords: Science & Technology
Physical Sciences
Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Chemistry
Physics
angle-resolved X-ray photoelectron spectroscopy (ARXPS)
density functional theory
electronic structure
ionic liquid mixture
surface science
RAY PHOTOELECTRON-SPECTROSCOPY
CATION-ANION INTERACTIONS
OUTER ATOMIC SURFACE
ELECTRONIC ENVIRONMENT
BINARY-MIXTURES
DENSITY
CATALYSIS
SUBSTITUENTS
SEGREGATION
SELECTIVITY
angle-resolved X-ray photoelectron spectroscopy (ARXPS)
density functional theory
electronic structure
ionic liquid mixture
surface science
Science & Technology
Physical Sciences
Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Chemistry
Physics
angle-resolved X-ray photoelectron spectroscopy (ARXPS)
density functional theory
electronic structure
ionic liquid mixture
surface science
RAY PHOTOELECTRON-SPECTROSCOPY
CATION-ANION INTERACTIONS
OUTER ATOMIC SURFACE
ELECTRONIC ENVIRONMENT
BINARY-MIXTURES
DENSITY
CATALYSIS
SUBSTITUENTS
SEGREGATION
SELECTIVITY
0306 Physical Chemistry (Incl. Structural)
0202 Atomic, Molecular, Nuclear, Particle And Plasma Physics
0307 Theoretical And Computational Chemistry
Chemical Physics
Publication Status: Published
Open Access location: https://onlinelibrary.wiley.com/doi/full/10.1002/cphc.201800216
Online Publication Date: 2018-05-11
Appears in Collections:Chemistry
Faculty of Natural Sciences



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