Infrared Spectroscopy of Li+ Solvation in EmimBF4 and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment

Infrared (IR) spectra of solutions of the lithium salt LiBF4in the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) and in the organic solvent propylene carbonate (PC) are studied via infrared spectroscopy and ab initio molecular dynamics (AIMD) simulations. The measurements show that the major effects of LiBF4in both solutions, compared to their neat counterparts, are the appearance of a new broad band in the 300-450 cm-1frequency region and a broadening of the IR structure in the 900-1200 cm-1region with the development of a new peak at 980 cm-1. Computational analysis indicates that hindered translational motions of Li+in its solvation cage are mainly responsible for the former, while the latter is due to Li+-induced structural changes and accompanying vibrational frequency shifts of constituent ions and molecules of the solutions. In addition, molecular motions in these and lower-frequency regions are generally correlated, disclosing the collective nature of the vibrational dynamics, which involve multiple ions/molecules. Herein, a detailed analysis of these features via AIMD simulations of the spectrum and its components arising from auto- and cross-correlations of motions of constituent molecular species, combined with generalized normal modes of the solutions and normal modes of small Li+-containing clusters, is presented. Other minor spectral changes caused by the lithium salt as well as the interaction-induced effect on IR spectra are also discussed.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry B, copyright © ACS Publications after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcb.2c06326.

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Work Title Infrared Spectroscopy of Li+ Solvation in EmimBF4 and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment
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Open Access
Creators
  1. Fangyong Yan
  2. Kallol Mukherjee
  3. Mark Maroncelli
  4. Hyung J. Kim
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Journal of Physical Chemistry B
Publication Date November 3, 2022
Publisher Identifier (DOI)
  1. https://doi.org/10.1021/acs.jpcb.2c06326
Deposited May 30, 2023

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Version 1
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  • Created
  • Added Li_manuscript_rev_fin.pdf
  • Added Creator Fangyong Yan
  • Added Creator Kallol Mukherjee
  • Added Creator Mark Maroncelli
  • Added Creator Hyung J. Kim
  • Published
  • Updated Work Title Show Changes
    Work Title
    • Infrared Spectroscopy of Li<sup>+</sup>Solvation in EmimBF<sub>4</sub>and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment
    • Infrared Spectroscopy of Li+ Solvation in EmimBF4 and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment
  • Updated