Molecular mobility in several imidazolium‐based ionic liquids according to data of ¹H and ¹³C NMR relaxation

Abstract

Temperature dependences are compared for H and C NMR 1/T curves relaxation rates in three imidazolium-based ionic liquids (ILs), namely, in [bmim]PF , [bmim]BF , and [emim]CH COO. C curves show alike behavior for all three ILs and follow a well-known Bloembergen-Pound-Purcell (BPP) equation. On the contrary, an essential part of H curves differ strongly from corresponding C ones and also have different shapes for different ILs. For the first time, we have detected the specific, two-maximum shape of H relaxation curve for hydrogen atom of C(2)H group of the [emim]CH COO. Assuming that this maximum reflects the correlated rotation of several adjoining ion pairs, we have tried to destroy this rotation by addition of glycerol to the [emim]CH COO. The second, high-temperature maximum has disappeared in the [emim]CH COO-glycerol mixture, and this fact confirms our assumption. Copyright © 2017 John Wiley & Sons, Ltd.

Molecular and Segmental Orientational Order in a Smectic Mesophase of a Thermotropic Ionic Liquid Crystal

“…A rotation/flip of the imidazolium core around N-C bond can also be accompanied by the chain re-alignment. The correlation of motion by ion-pairing, as has been observed in isotropic phase of ionic liquids, may impose additional restriction on the core dynamics [26][27][28][29]. On the other hand, diffusion and conductivity studies have indicated (partial) dissociation of cations and anions in mesophases [28][29][30].…”

Translational Diffusion in a Set of Imidazolium-Based Ionic Liquids [bmim]+A– and Their Mixtures with Water

“…A more detailed overview of works in the outlined area is presented in papers and reviews. ,,,,,,− ,,− Note in addition that in a series of works, Abe and co-authors − hypothesized the existence of “water pockets” in the structure of solutions at a water concentration of approximately 70–90 mol %. It was reported that such formations manifested an abnormal behavior of water, and we discuss here the problem in details.…”

Molecular Mobility in a Set of Imidazolium-Based Ionic Liquids [bmim]+A– by the NMR-Relaxation Method

“…Some other significant results on IL/RTILs have been presented and discussed in many reviews. 4,7,19,20,30,64,65 Despite numerous works, some important gaps in studies still remain. One of those gaps is the absence of multinuclear NMR relaxation experiments for the wide series of neat RTILs with altering anions or cations, similar to what was done in the study of chemical shifts or self-diffusion coefficients.…”