Voronoi Polyhedra as a Tool for the Characterization of Inhomogeneous Distribution in 1-Butyl-3-methylimidazolium Cation-Based Ionic Liquids

Abstract

The inhomogeneity distribution in four imidazolium-based ionic liquids (ILs) containing the 1-butyl-3-methylimidazolium (C 4 mim) cation, coupled with tetrafluoroborate (BF 4 ), hexafluorophosphate (PF 6 ), bis(trifluoromethanesulfonyl)amide (TFSA), and trifluoromethanesulfonate (TfO) anions, was characterized using Voronoi polyhedra. For this purpose, molecular dynamic simulations have been performed on the isothermal−isobaric (NpT) ensemble. We checked the ability of the potential models to reproduce the experimental density, heat of vaporization, and transport properties (diffusion and viscosity) of these ionic liquids. The inhomogeneity distribution of ions around the ring, methyl, and butyl chain terminal hydrogen atoms of the C 4 mim cation was investigated by means of Voronoi polyhedra analysis. For this purpose, the position of the C 4 mim cation was described successively by the ring, methyl, and butyl chain terminal hydrogen atoms, while that of the anions was described by their F or O atom. We calculated the Voronoi polyhedra distributions of the volume, the density, and the asphericity parameters as well as that of the radius of the spherical intermolecular voids. We carried out the analysis in two steps. In the first step, both ions were taken into account. The calculated distributions gave information on the neighboring ions around a reference one. In the second step, to distinguish between like and oppositely charged ions and then to get information on the inhomogeneity distribution of the like ions, we repeated the same calculations on the same sample configurations and removed one of the ions and considered only the other one. Detailed analysis of these distributions has revealed that the ring hydrogen atoms are mainly solvated by the anions, while the methyl and butyl terminal H atoms are surrounded by like atoms. The extent of this inhomogeneity was assessed by calculating the cluster size distribution that shows that the dimers are the most abundant ones.

Evaluation of static differential capacitance at the [C4mim+][TFSA−]/electrode interface using molecular dynamics simulation combined with electrochemical surface plasmon resonance measurements

“…we used an all-atom nonpolarizable force field CL&P, 62 which has been widely used for the MD simulation of IL composed of imidazolium cations [63][64][65] and TFSA − anion. [64][65][66][67] Fig.…”

“…we used an all-atom nonpolarizable force field CL&P, 62 which has been widely used for the MD simulation of IL composed of imidazolium cations [63][64][65] and TFSA − anion. [64][65][66][67] Fig. 1 shows the structures of the C4mim + cation and TFSA − anion used in our simulations with characteristic length marked.…”

Development of Imidazolium-Based Parameters for AMOEBA–IL

“…A number of possible applications has been investigated, including (but not limited to) electrolytes for batteries, lubricants, organic solvents substitutes, biocatalysis, etc. [5,6,7,8,9,10,11,12].…”

Anion Effects on the Mixing States of 1-Methyl-3-octylimidazolium Tetrafluoroborate and Bis(trifluoromethylsulfonyl)amide with Methanol, Acetonitrile, and Dimethyl Sulfoxide on the Meso- and Microscopic Scales

“…These macroscopic properties mainly arise from the microscopic interaction of anions with the imidazolium ring of the ILs depending on the charge density and the chemical structure of the anions. The interactions between the imidazolium ring of C 4 mim + with the butyl chain and several anions, such as BF 4 – , PF 6 – , TFSA – , and trifluoromethanesulfonate (TfO – ), have been clarified by molecular dynamics (MD) simulations with Voronoi polyhedral (VP) analysis . The distributions of the anions around C 4 mim + have been evaluated from the VP data.…”

“…The interactions between the imidazolium ring of C 4 mim + with the butyl chain and several anions, such as BF Voronoi polyhedral (VP) analysis. 6 The distributions of the anions around C 4 mim + have been evaluated from the VP data.…”