The liquid surface of chiral ionic liquids as seen from molecular dynamics simulations combined with intrinsic analysis

Aqueous solutions of hydroxyl-functionalized ionic liquids: Molecular dynamics studies

A series of aqueous solutions of 1-(n-hydroxyalkyl)-3-(n-hydroxyalkyl) imidazolium bromide ([HOC_nC_mOHIm][Br], with n and m = 2, 6,10 and 14) were studied by atomistic molecular dynamics simulations. Structural properties were characterized by the radial distribution functions between different pairs, angular distributions and aggregation numbers. Dynamics of the system has been investigated by computing the diffusion of the ions and molecules. Structures of the aggregates formed depend upon the length of the hydroxyalkyl chains. The long-distance spatial correlations observed in solutions with cations having long chain substituent are arising due to the formation of intercalated structures. A thin film like structure is formed in solutions having longer hydroxyalkyl chains, with the structure stabilized by the dispersion interactions between the interdigitated alkyl chains and the hydrogen bond formation between the hydroxyl group of a cation with head group of a different cation. Anions are dispersed near the surface of the film.

Molecular-level insights into the structures, dynamics, and hydrogen bonds of ethylammonium nitrate protic ionic liquid at the liquid-vacuum interface

A series of molecular dynamics simulations have been used to systematically explore the structures, dynamics and hydrogen bonds (HBs) of ethylammonium nitrate (EAN) protic ionic liquid (IL) and their mutual relationship at the liquid-vacuum interface. The simulation results clearly demonstrate that there exists a sandwich structure at the interface, with the double-layer of the EA+ cations on both sides and one intercalated layer of the NO3- anions in the middle. Wherein, the outermost cation layer prefers the orientation with the CH3 groups pointing to the vacuum phase due to the hydrophobic interactions, while the CH3 groups in the second layer direct to the bulk liquid phase owing to the HB formation between their NH3+ groups and the intercalated NO3- anions in the middle layer. On the other hand, the continuous HB strength of the cations in the outermost layer (denoted as Cation-1) is found to be almost identical with the counterpart of the cations in the second layer (denoted as Cation-2), whereas the intermittent HB strength of Cation-1 is much larger than that of Cation-2 at all temperatures. Furthermore, the rotational motion of Cation-1 with the normal vector of the C-C-N plane in the cation is faster than that of Cation-2 with the same vector, resulting from more free space in the outermost layer. On the contrary, the rotational motion of Cation-1 with the vector from the mass center of the cation to its N atom is much slower than that of Cation-2 with the same vector, which can be attributed to the combined effects of the stronger intermittent HBs of Cation-1 and the hydrophobic interactions of its CH3 group in the outermost layer.

Computational approaches to understanding reaction outcomes of organic processes in ionic liquids

The utility of using a combined experimental and computational approach for understanding ionic liquid media, and their effect on reaction outcome, is highlighted through a number of case studies.

The ionic liquid–vacuum outer atomic surface: a low-energy ion scattering study

We have identified elements present in the ionic liquid–vacuum outer atomic surface of 23 ionic liquids using high sensitivity low-energy ion scattering (LEIS), a very surface sensitive technique.