Non‐Ideal Mixing Behaviour of Hydrogen Bonding in Mixtures of Protic Ionic Liquids

Abstract

Ionic liquids (ILs) attract interest in science and technology as a result of their unique properties. Binary and ternary mixtures of ILs significantly increase the number of possible cation/anion combinations, resulting in targeted physical and chemical properties. In this work, we study the mixing behaviour of two protic ILs: triethyl ammonium methylsulfonate [Et3 NH][CH3 SO3 ] and triethylammonium triflate [Et3 NH][CF3 SO3 ]. We find a characteristic deviation from ideal mixing by means of low-frequency infrared spectroscopy. By using molecular dynamics simulations, we explain this behaviour as being the result of different strengths of anion/cation hydrogen bonding. This non-ideality of non-random H-bond mixing is also reflected in macroscopic properties such as the viscosity. Mixing suitable ILs may, thus, result in new ILs with targeted physical properties.

Hydrogen bonding in a mixture of protic ionic liquids: a molecular dynamics simulation study

“…We would like to point out that physical properties reported in these studies, such as the density and the viscosity, were mostly exhibiting ideal-like mixing behavior in the sense that the properties vary almost linearly with the mixture composition. 16 A population analysis as a function of mixture-composition is suggesting a favorable interaction of TEA with the methylsulfonate-ion. 10,11 Recently, Welton and co-workers have commented on the tendency for ideal-mixture behavior in mixtures of ionic liquids and reviewed IL mixtures with a focus on property design an opportunities for applications.…”

“…5,6,[9][10][11][12][13] However, mostly the behavior of aprotic ionic liquids has been considered so far. 16 Using far-infrared spectroscopy, we could assign signatures distinguishing between hydrogen-bonded aggregates of TEA to each of the two anions within the mixture. In addition, also the molar mixing-enthalpies and -entropies indicated only a small deviation from the ideal mixture-behavior.…”

“…In addition, also the molar mixing-enthalpies and -entropies indicated only a small deviation from the ideal mixture-behavior. 16 With the present study we would like to complement our earlier endeavour with an in-depth analysis of a detailed molecular model of the same binary TEATMS-TEATF mixture, focusing on the local solvation-structure of the ions, and, in particular, a Universität Rostock, Institut für Chemie, Abteilung Physikalische und Theoretische on the hydrogen-bonding. 5,9 The situation seems to be different for protic ionic liquids, where strongly directional hydrogen-bonds (can) exist.…”

Triphilic Ionic‐Liquid Mixtures: Fluorinated and Non‐fluorinated Aprotic Ionic‐Liquid Mixtures

“…Furthermore, the non-ideal mixing behavior of hydrogen bonding in mixtures of protic ILs has been studied by far-IR spectroscopy measurements supported by MD simulations by the Ludwig group. [10] In another article, a detailed MD analysis is given for the non-ideal mixing behavior explained by simple lattice models. [17]…”

The Effect of C4H and C5H on the Microstructure of Aqueous Solutions of 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids

“…[12,15] Unfortunately,u ntil now the influence of the interactions of the C4ÀHa nd C5ÀHp rotons on the microstructure and physicochemical properties was poorly understood.T herefore, in this work, the microstructures of [Emim]BF 4 -watera nd [Bmim]BF 4 -water mixtures were studied throught he concentration-dependent 1 HNMR chemicals hifts including three aromatic protons (C sp 2ÀH) of the ILs and ah ydroxy proton (OÀH) of water.M oreover,t he relative 1 HNMR chemicals hifts and local composition (LC) model [29] were employed to evaluate the effect of the interactions of C4ÀHa nd C5ÀHo nt he microstructure of the systems. Finally,t ov erify the influence of the interactions of C4ÀHa nd C5ÀHo nt he microstructure, as well as to better understand the relationship between the microstructure andp hysicochemical properties, the viscosity of the studied systems, which can be related to hydrogen-bonding interactions, [8] was predicted with the Eyring-UNIQUAC equationb yu sing the interaction-energy parameters obtained from the 1 HNMR chemical shifts of the studied C sp 2ÀHa nd OÀH, and the prediction results of viscosity were used to confirm the influence of C4ÀHa nd C5ÀHo nt he microstructure.…”