Effect of SO2 on the Transport Properties of an Imidazolium Ionic Liquid and Its Lithium Solution

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• 作者：Marcelo J. Monteiro ; Ro虃mulo A. Ando ; Leonardo J. A. Siqueira ; Fernanda F. Camilo ; Paulo S. Santos ; Mauro C. C. Ribeiro ; Roberto M. Torresi
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：August 11, 2011
• 年：2011
• 卷：115
• 期：31
• 页码：9662-9670
• 全文大小：1052K
• 年卷期：v.115,no.31(August 11, 2011)
• ISSN：1520-5207

文摘

Transport coefficients have been measured as a function of the concentration of sulfur dioxide, SO₂, dissolved in 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [BMMI][Tf₂N], as well as in its lithium salt solution, Li[Tf₂N]. The SO₂ reduces viscosity and density and increases conductivity and diffusion coefficients in both the neat [BMMI][Tf₂N] and the [BMMI][Tf₂N]鈥揕i[Tf₂N] solution. The conductivity enhancement is not assigned to a simple viscosity effect; the weakening of ionic interactions upon SO₂ addition also plays a role. Microscopic details of the SO₂ effect were unraveled using Raman spectroscopy and molecular dynamics (MD) simulations. The Raman spectra suggest that the Li⁺鈥揫Tf₂N] interaction is barely affected by SO₂, and the SO₂鈥揫Tf₂N] interaction is weaker than previously observed in an investigation of an ionic liquid containing the bromide anion. Transport coefficients calculated by MD simulations show the same trend as the experimental data with respect to SO₂ content. The MD simulations provide structural information on SO₂ molecules around [Tf₂N], in particular the interaction of the sulfur atom of SO₂ with oxygen and fluorine atoms of the anion. The SO₂鈥揫BMMI] interaction is also important because the [BMMI] cations with above-average mobility have a larger number of nearest-neighbor SO₂ molecules.