Pressure-induced Raman spectral changes of N,N,diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate

Abstract

We have measured Raman spectral changes in one of the aliphatic series of ionic liquids, N,N,diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF₄], under high pressure. Although the [DEME] cation has mainly two stable conformers of TG ⁺−tg ⁺ t and TG ⁺−g ⁺ g ⁻ t in the liquid state, the population of the minor conformer, i.e. TG ⁺−g ⁺ g ⁻ t, decreases with increasing pressure. The difference in the partial molar volume between the two conformers was determined from the pressure dependence of the relative Raman intensity ratio.

Keywords:

• room temperature ionic liquids
• diamond anvil cell
• partial molar volume
• conformational equilibrium

Acknowledgments

We appreciate Professor T. Arai and Dr M. Aono for their helpful discussions.