Conformational Analysis of Quaternary Ammonium-Type Ionic Liquid Cation, N,N-Diethyl-N-methyl-N-(2-methoxyethyl) Ammonium Cation

Abstract

Conformational preference of N,N-diethyl- N-methyl- N-(2-methoxyethyl) ammonium cation ([DEME] +), which is one of the quaternary ammonium-based ionic liquid cation, in the gas phase has been investigated using a density functional theory (DFT) calculation. Eight candidates for the stable conformers of [DEME] + exist in the gas phase, and can it energetically classify into two groups. One is a five conformers group, which has the N + ⋯ O − intramolecular attractive interaction form (the folded form). The other is a three conformers group, which is the noninteraction form (the extended form). The transformation from the folded form to the extended form induces large changes in the dipole moment and partial charges of N and O atoms. Here we show that the difference in the dipole moment and partial charges of N and O atoms associated with the conformational change of [DEME] + are closely related to the molecular orientation of [DEME]-based ionic liquids in the liquid state.