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Title: Interaction between ionic liquid cation and water: Infrared predissociation study of [bmim] +·(H 2O) n clusters

Abstract

The infrared predissociation spectra of [bmim] +·(H 2O) n, n = 1–8, in the 2800–3800 cm –1 region are presented and analyzed with the help of electronic structure calculations. The results show that the water molecules solvate [bmim]+ by predominately interacting with the imidazolium C2–H moiety for the small n = 1 and 2 clusters. This is characterized by a redshifted and relatively intense C2–H stretch. For n ≥ 4 clusters, hydrogen-bond interactions between the water molecules drive the formation of ring isomers which interact on top of the imidazolium ring without any direct interaction with the C2–H. The water arrangement in [bmim]+·(H 2O) n is similar to the low energy isomers of neutral water clusters up to the n = 6 cluster. This is not the case for the n = 8 cluster, which has the imidazolium ring disrupting the otherwise preferred cubic water structure. Here, the evolution of the solvation network around [bmim]+ illustrates the competing [bmim]+–water and water–water interactions.

Authors:
 [1];  [1];  [1];  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1358403
Grant/Contract Number:
SC0010326
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 28; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Voss, Jonathan M., Marsh, Brett M., Zhou, Jia, and Garand, Etienne. Interaction between ionic liquid cation and water: Infrared predissociation study of [bmim]+·(H2O)n clusters. United States: N. p., 2016. Web. doi:10.1039/c6cp02730j.
Voss, Jonathan M., Marsh, Brett M., Zhou, Jia, & Garand, Etienne. Interaction between ionic liquid cation and water: Infrared predissociation study of [bmim]+·(H2O)n clusters. United States. doi:10.1039/c6cp02730j.
Voss, Jonathan M., Marsh, Brett M., Zhou, Jia, and Garand, Etienne. 2016. "Interaction between ionic liquid cation and water: Infrared predissociation study of [bmim]+·(H2O)n clusters". United States. doi:10.1039/c6cp02730j. https://www.osti.gov/servlets/purl/1358403.
@article{osti_1358403,
title = {Interaction between ionic liquid cation and water: Infrared predissociation study of [bmim]+·(H2O)n clusters},
author = {Voss, Jonathan M. and Marsh, Brett M. and Zhou, Jia and Garand, Etienne},
abstractNote = {The infrared predissociation spectra of [bmim]+·(H2O)n, n = 1–8, in the 2800–3800 cm–1 region are presented and analyzed with the help of electronic structure calculations. The results show that the water molecules solvate [bmim]+ by predominately interacting with the imidazolium C2–H moiety for the small n = 1 and 2 clusters. This is characterized by a redshifted and relatively intense C2–H stretch. For n ≥ 4 clusters, hydrogen-bond interactions between the water molecules drive the formation of ring isomers which interact on top of the imidazolium ring without any direct interaction with the C2–H. The water arrangement in [bmim]+·(H2O)n is similar to the low energy isomers of neutral water clusters up to the n = 6 cluster. This is not the case for the n = 8 cluster, which has the imidazolium ring disrupting the otherwise preferred cubic water structure. Here, the evolution of the solvation network around [bmim]+ illustrates the competing [bmim]+–water and water–water interactions.},
doi = {10.1039/c6cp02730j},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 28,
volume = 18,
place = {United States},
year = 2016,
month = 6
}

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  • Composition dependent structural and dynamical properties of aqueous hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF{sub 6}]) ionic liquid (IL) have been investigated by using all-atom molecular dynamics simulation. We observe that addition of water does not increase significant number of dissociated ions in the solution over the pure state. As a consequence, self-diffusion coefficient of the cation and anion is comparable to each other at all water concentration similar to that is observed for the pure state. Voronoi polyhedra analysis exhibits strong dependence on the local environment of IL concentration. Void and neck distributions in Voronoi tessellation are approximately Gaussian for pure ILmore » but upon subsequent addition of water, we observe deviation from the Gaussian behaviour with an asymmetric broadening with long tail of exponential decay at large void radius, particularly at higher water concentrations. The increase in void space and neck size at higher water concentration facilitates ionic motion, thus, decreasing dynamical heterogeneity and IL reorientation time and increases self-diffusion coefficient significantly.« less
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