Jump to main content
Jump to site search

Issue 25, 2011
Previous Article Next Article

Simulations of photoemission and equilibrium redox processes of ionic liquids: the role of ion pairing and long-range polarization

Author affiliations

Abstract

We have studied oxidation and reduction of ionic liquids using methods of theoretical chemistry. In particular, we have modeled photoelectron spectra of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) ionic liquids and their components. We have considered ion pairs in the gas phase and solvated in the water represented by a dielectric continuum. We have also characterized the isolated cation and anion of the ionic liquids. The calculated quantities have been compared with available experiments. The photoelectron spectra were modeled within linearized reflection approximation, using a composite ab initio approach based on combination of the MP2 method for the ground state, the PMP2 method for the first ionized electronic state and the TDDFT method to estimate the higher ionization energies. We have also briefly explored energetics of processes following the vertical electron attachment/detachment. Our calculations were able to reproduce the measured photoelectron spectra. We have shown that the valence photoelectron spectrum results from simultaneous ionization from many molecular orbitals. In the threshold region, the electron is ejected from the anion in the gas phase ion pair while the cationic moiety is ionized when the ion pair is solvated. We have investigated the effect of both short-range and long-range interactions on the ionization characteristics, showing that the long-range polarization of the solvent effectively screens the specific short-range interactions. The large difference between the HOMO–LUMO gap and the electrochemical window has been rationalized in terms of relaxation following the redox processes, i.e. solute and solvent geometric relaxation and reactions, e.g. dimerization of the imidazolium radical formed during the reduction.

Graphical abstract: Simulations of photoemission and equilibrium redox processes of ionic liquids: the role of ion pairing and long-range polarization

Back to tab navigation

Supplementary files

Publication details

The article was received on 01 Mar 2011, accepted on 05 May 2011 and first published on 31 May 2011


Article type: Paper
DOI: 10.1039/C1CP20570F
Citation: Phys. Chem. Chem. Phys., 2011,13, 11998-12007
  •   Request permissions

    Simulations of photoemission and equilibrium redox processes of ionic liquids: the role of ion pairing and long-range polarization

    L. Šištík, M. Ončák and P. Slavíček, Phys. Chem. Chem. Phys., 2011, 13, 11998
    DOI: 10.1039/C1CP20570F

Search articles by author

Spotlight

Advertisements