Influence of the anion on the properties of ionic liquid mixtures: a molecular dynamics study

Abstract

Mixing of ionic liquids provides new opportunities for their tuning, enabling the applications of ionic liquid mixtures to expand. At the same time, the genesis of the fundamental properties of ionic liquid mixtures is still poorly understood. In this study we carried out a molecular dynamics simulation of binary mixtures of 1-buthyl-3-methylimidazolium hexafluorophosphate, 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-buthyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate ([C4mim][PF6] + [C4mim][NTf2], [C4mim][PF6] + [C4mim][FAP], [C4mim][FAP] + [C4mim][NTf2]) in a wide concentration range at 303.15 K and complemented it with quantum mechanical calculations. Three pure ionic liquids underwent the same kind of analysis for comparison purposes. We found that the addition of the [FAP]--anion to a mixture enhances the segregation of non-polar domains and weakens the hydrogen-bond network. The H-bonds in the studied mixtures are rather weak, as follows from QTAIM analysis, with the rarest occurrence for the [FAP]--anion. The competition of two anions in the mixtures for the most acidic hydrogen of the 1-butyl-3-methylimidazolium cation is reported. In most of the cases, the smaller anion ([PF6]- or [NTf2]-) with stronger charge concentration displaces the bigger one ([NTf2]- or [FAP]-) from the preferred coordination site. The existing nano-segregation in some mixtures notably slows down ion diffusion. Our results show that the differences in anion size, shape and nature are the main reasons for nano-segregation and the non-ideal behavior of ionic liquid mixtures.

Predictive energetic tuning of C-Nucleophiles for the electrochemical capture of carbon dioxide

“…To verify this correlation for imidazolium salts, we measured E red for a family of imidazolium salts ( Figure S1 and Table S1 ) using normal pulse voltammetry (NPV). While the influence of ion pairing and association on properties of imidazolium salts has been well documented in the ionic liquid literature ( Tsuzuki et al., 2013 ; Voroshylova et al., 2018 ; Wang et al., 2015 ), the nature of the counterion's effects on our measurements is minimized through the use of NBu 4 PF 6 , an electrolyte with a chemically stable, non-coordinating PF 6 − anion. Furthermore, we validated the observation that one-electron reductions of imidazolium cations produce free NHCs and verified that this applies to the analogous imidazolinium cations with non-aromatic, saturated backbones.…”

Computational Modelling and Sustainable Synthesis of a Highly Selective Electrochemical MIP-Based Sensor for Citalopram Detection

“…Self-diffusion coefficients were only evaluated after examining the attainment of a diffusive regime. To accomplish this, the parameter β was computed for each species and each simulation cell, as comprehensively described elsewhere [ 58 , 59 , 60 , 61 ]. The GRACE software was used for the numerical integration of RDFs for coordination numbers (CNs) assessment.…”

NaRIBaS—A Scripting Framework for Computational Modeling of Nanomaterials and Room Temperature Ionic Liquids in Bulk and Slab

“…In work [24], we used the NaRIBaS workflow from Figure 4 to mix up to three types of ions into liquid mixtures and then simulate their properties. To introduce NaRIBaS, we choose Gromacs software package, version 5.1.4.…”

“…A sample workflow for conducting similar simulations is provided in the IL-mix folder of the NaRIBaS GitHub repository (Reference [15]). In work [24], we used the NaRIBaS workflow from Figure 4 to mix up to three types of ions into liquid mixtures and then simulate their properties. To introduce NaRIBaS, we choose Gromacs software package, version 5.1.4.…”