Intermolecular interactions, ion solvation, and association in mixtures of 1-<i>n</i>-butyl-3-methylimidazolium hexafluorophosphate and γ-butyrolactone: Insights from Raman spectroscopy - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Raman Spectroscopy Année : 2015

Intermolecular interactions, ion solvation, and association in mixtures of 1-n-butyl-3-methylimidazolium hexafluorophosphate and γ-butyrolactone: Insights from Raman spectroscopy

Résumé

By means of Raman spectroscopy coupled with density functional theory (DFT) calculations and perturbation correlation moving window two-dimensional correlation spectroscopy intermolecular interactions were assessed in mixtures of ionic liquid (IL) 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) with polar aprotic solvent γ-butyrolactone (γ-BL) over the entire range of compositions. The symmetrical P―F stretching vibration of the IL anion was found to be insensitive to the changes in mixture concentration in contrast to the C[DOUBLE BOND]O stretching vibration of the γ-BL and the imidazolium ring C―H stretching vibrations of the IL cation. Each of these vibrational profiles was decomposed in various spectral contributions, and their number was rationalized by the results of quantum-chemical calculations and/or previous controversial published data. Progressive redshift of the ring C―H stretching wavenumbers was referred to pronounced solvation of the cation at the imidazolium ring site accompanied with H-bond formation. This was especially pronounced at IL mole fraction less than 0.18. Complicated variations in the intensities of the individual contributions of the C[DOUBLE BOND]O profile were treated as a manifestation of the changing with concentration pattern of the intermolecular interactions. The self-association of γ-BL molecules and distinct cation solvation as dominant intermolecular interactions at low IL content are replaced with weaker cation solvation and ion association at high concentrations of IL. Possible representative molecular structures were proposed on the basis of DFT calculations.

Dates et versions

hal-01135915 , version 1 (26-03-2015)

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B. Marekha, V.A. Koverga, M. Moreau, M. Kiselev, T. Takamuku, et al.. Intermolecular interactions, ion solvation, and association in mixtures of 1-n-butyl-3-methylimidazolium hexafluorophosphate and γ-butyrolactone: Insights from Raman spectroscopy. Journal of Raman Spectroscopy, 2015, 46, pp.339 - 352. ⟨10.1002/jrs.4640⟩. ⟨hal-01135915⟩
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