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

Abstract

We present a comprehensive molecular dynamics simulation study on 1-butyl-3-methylimidazolium ionic liquids and their fluorinated analogs. The work focused on the effect of fluorination at varying anions. The main findings are that the fluorination of the cations side chain increases overall structuring, especially the aggregation of cation side chain. Furthermore, large and weakly coordinating anions tend to occupy on-top positions of the cation and decrease the aggregation of cation side chains, most likely due to enhanced alkyl-anion interaction.

Thermophysical properties of imidazolium tricyanomethanide ionic liquids: experiments and molecular simulation

“…This can be related with a higher structural organization in the bulk liquid. 85,86 A higher dependency of the densities on the alkyl chain length of the cation is observed for the ILs with fluorine-based anions. As the alkyl chain increases, the higher organization of the fluorinated ILs is more affected leading to a higher contribution of the methylene group, -CH 2 -, to the density decrease.…”

“…This can be related with the stronger ion pairing of the fluorinated ILs as a result of their higher dispersive interactions. 85 The anion effect on the densities was further explored considering a common cation, 1-butyl-3-methylimidazolium cation ([C 4 mim] + ). The representation of the densities at 298.15 K against the molar mass of the anion is shown in Fig.…”

Local Structure in Terms of Nearest-Neighbor Approach in 1-Butyl-3-methylimidazolium-Based Ionic Liquids: MD Simulations

“…Two typical kinds of contacts have been reported in imidazolium-based ILs: tail-tail and ring-ring (e.g., π + -π + stacking). 1,11,39,74 The former one is known to be at the origin of microheterogeneity observed both experimentally 1,[77][78] and by molecular simulations.…”

“…We begin our analyses with a basic characterization of the relative arrangement of anions around a 39 However, these RDFs show little detail (see Figure S2) as they sample all the possible orientations of the vector connecting the reference and observed sites.…”

“…Nonetheless, we highlight the works of Kirchner et al [37][38][39] in which the systematic selection of anions has been combined with a detailed analysis of the microscopic structure. Namely Figure 1 for molecular structures).…”