Surface Enrichment in Equimolar Mixtures of Non-Functionalized and Functionalized Imidazolium-Based Ionic Liquids

Heller B, Kolbeck C, Niedermaier I, Dommer S, Schatz J, Hunt P, Maier F, Steinrück HP (2018)

Publication Type: Journal article, Original article

Publication year: 2018

Journal

ChemPhysChem Wiley

Book Volume: 19

Pages Range: 1733-1745

DOI: 10.1002/cphc.201800216

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 hexafluorophos
phate+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 correspond
ing 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-functional
ized cations. Calculations of the electronic structure and the
intramolecular partial charge distribution of the cations contrib
ute to interpreting these shifts for the two different cations.



Authors with CRIS profile

Bettina Heller Lehrstuhl für Physikalische Chemie II Claudia Kolbeck Lehrstuhl für Physikalische Chemie II Inga Niedermaier Lehrstuhl für Physikalische Chemie II Sabine Dommer Professur für Organische Chemie Jürgen Schatz Professur für Organische Chemie Florian Maier Lehrstuhl für Physikalische Chemie II Hans-Peter Steinrück Lehrstuhl für Physikalische Chemie II

How to cite

APA:

Heller, B., Kolbeck, C., Niedermaier, I., Dommer, S., Schatz, J., Hunt, P.,... Steinrück, H.-P. (2018). Surface Enrichment in Equimolar Mixtures of Non-Functionalized and Functionalized Imidazolium-Based Ionic Liquids. ChemPhysChem, 19, 1733-1745. https://dx.doi.org/10.1002/cphc.201800216

MLA:

Heller, Bettina, et al. "Surface Enrichment in Equimolar Mixtures of Non-Functionalized and Functionalized Imidazolium-Based Ionic Liquids." ChemPhysChem 19 (2018): 1733-1745.

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