Liquid structure of 1, 3-dimethylimidazolium salts

Abstract

The structure of liquid 1, 3-dimethylimidazolium hexafluorophosphate is described in detail and compared with the structure of 1, 3-dimethylimidazolium chloride. In each case, the data were obtained from neutron diffraction experiments and analysed using an empirical potential structure refinement process. Overall, the structures are similar; however, significant differences arise from the variation in anion size.

Structures of Ionic Liquids with Different Anions Studied by Infrared Vibration Spectroscopy

“…Previous reports also suggested the BF 4 -and PF 6 -anions are located out of the imidazolium ring plane. 9,15,20,24 More definitely, any specific interaction or proximity with the imidazolium ring proton is unlikely, as that would be reflected as a peak shift or change in , the iodine anion should be near H-C(2) to promote deuterium exchange. We further suggest it would lie close to the plane made by the imidazolium ring, such that I -‚‚‚H-C(2) forms a near-linear hydrogen bond.…”

“…Our proposition on the relative location between the anion and cation is similar to the conclusion from recent molecular dynamics simulation with similar systems of [ 6 ] was in favor of the proposition made in this study. 24 Figure 9 shows the proposed anion positions in (Figure 9a) [BMIM][BF 4 ] and (Figure 9b) [BMIM][I], where BF 4 -is positioned on top of the imidazolium ring, while the I -lies in the imidazolium ring plane, close to H-C(2) and presumably a bit off from the bond direction to account for the increased peak strength of ν AS HC(4)C(5)H.…”

“…4,16,[18][19][20][21][22][23] By contrast, there have been several simulation studies and experiments which proposed that the difference in the relative position is very small for different anion types. 9,15,24 Thus, even for prototypical imidazolium ionic liquid, this issue is still unresolved and awaits further investigation, especially as the relative position between the cation and the anion is one of the most important structural information.…”

Novel 2-alkyl-1-ethylpyridinium ionic liquids: synthesis, dissociation energies and volatility

“…[1][2][3][4][5][6] This characteristic of the structural organization of ionic liquids was first experimentally supported by X-ray diffraction 7 and later by small-wide angle X-ray scattering (SWAXS). 8,9 Neutron diffraction was used to study the structures of 1,3-dimethylimidazolium chloride, 10 [C 1 C 1 im] [Cl], and hexafluorophosphate, 11 [C 1 C 1 im][PF 6 ], ionic liquids. The comparison of diffraction patterns of deuterated and protonated liquids provides a detailed picture of the anioncation and cation-cation interactions.…”

“…It was also observed that the degree of charge ordering becomes less pronounced for large anions and asymmetrical cations. [10][11][12][13] Recently, a combination of infrared (IR) spectroscopic techniques was used to characterize the degree of charge organization present in the imidazolium based ionic liquid family. 14 It was found that longer alkyl side chains attached onto the imidazolium ions increase the short-range repulsive interactions among the ions and disrupt the charge organization, in agreement with previous studies.…”