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 [C(2)C(1)im][C(2)SO(4)]. 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.

Side chain fluorination and anion effect on the structure of 1-butyl-3-methylimidazolium ionic liquids

“…This leads to the assumption that dispersion interaction is crucial for the population of on-top positions, which is supported by recent results of Hunt 120 and our group. 109,110 …”

“…The second conformation is the on-top conformation, where the anion is above or below the ring center, see the ring and the side chain in gg or gt conformation of the same cation. 95,109,110,114,[118][119][120][121] To examine such coordination behavior, a combined distribution function containing the distance d CoR(+) − X(−) and the angle (r RN , r CoR(+) − X(−) ), where CoR(+) is the center of the imidazolium ring, RN is the ring normal of the same ring, and X(−) are the coordinating atoms of the anion, is employed. Representative CDFs are presented in Fig.…”

En route formation of ion pairs at the ionic liquid–vacuum interface

“…Similarly to the coordination numbers, a gradual change can be observed in the average conformation, from about 1200 pm below the surface for the ½C 2 C 1 im½C 2 SO 4 IL. Throughout this interval, the C7'(A)-CoR distances increase, which means that the anion's ethyl group moves away from the cation's ring and is elongated the most in the gas phase [19]. This displacement is in accordance with the slight decrease in the distances between the centers of charge (CoC); thus, the charged, and therefore more interacting sulfate oxygen atoms turn to face the cationic ring, while the anionic side chain is moving away from it.…”

“…Considering these fundamentally different structural features, the process of vaporization is apparently not as trivial as for molecular solvents, and significant structural rearrangement has to occur en route from the bulk to the vapor. The vaporization process, therefore, should involve not only the diffusion to the surface, but also the formation of the vaporizable entity, and-since it consists of two molecules, and hence it is more flexible than the molecular solventsalso its rearrangement in the gas phase may be of great importance [19,20].…”

Mapping the Free Energy of Lithium Solvation in the Protic Ionic Liquid Ethylammonuim Nitrate: A Metadynamics Study

“…The electronic structure properties were calculated using the PBE [87] functional with the empirical correction from Grimme scheme (DFT-D3) [88,89] to account for the dispersion interactions, which are important in ionic liquids [90][91][92] . Kohn-Sham orbitals are expanded in a Gaussian basis set for the all atoms (MOLOPT-DZVP-SR-GTH for Li, C, N, O, H), and we employed the norm-conserving GTH pseudopotentials.…”