The bulk and the gas phase of 1-ethyl-3-methylimidazolium ethylsulfate: dispersion interaction makes the difference

Abstract

Ab initio molecular dynamics simulations were carried out on systems representing the gas and the bulk phase of 1-ethyl-3-methylimidazolium ethylsulfate [C₂C₁im][C₂SO₄]. The power spectra and cation–anion spatial distribution revealed different interactions of the anion and cation in the bulk phase versus the gas phase. In the bulk phase, all oxygen atoms of the anions are involved and interaction via the rear hydrogen atoms is possible, forming a closer packed system. The alkyl groups of cations and anions governed by dispersion interaction stick together in the bulk but are relatively free in the gas phase.