Microscopic study of binary mixtures between pyrrolidinium bis(triflorosulfonyl)imide and dimethyl sulfoxide/acetonitrile

Abstract

Molecular interactions of a representative pyrrolidinium-based ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(triflorosulfonyl)-imide ([BMPyrr][TFSI]) with dimethyl sulfoxide (DMSO) and acetonitrile (AN) have been analyzed in this work. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and density functional theory (DFT) calculations are used in the investigation, while excess infrared spectra and two-dimensional correlation spectroscopy are used to explore the data in detail. It has been found that the molecular solvents can interact with TFSI  (mainly with S=O and weakly with S-N-S group). AN interacts feebly with BMPyrr + as compared with the strong interaction of DMSO. The strength of the interactions depends on the electron donating ability of the solvent. Upon mixing, hydrogen bonds regarding C−Hs in cation and S-N-S in anion are weakened, while that regarding S=O in anion is strengthened. Among the C−Hs which are connected directly with the N of the cation, C1−H is the main interaction site for both DMSO and AN. This means that C1−H is the most acidic hydrogen in pyrrolidinium cation. ATR-FTIR, DFT calculations, excess infrared spectrum, two-dimensional correlation spectroscopy, ionic liquid, hydrogen bondCitation:

Evidence that Acetonitrile is Sensitive to Different Interaction Sites of Ionic Liquids as Revealed by Excess Spectroscopy

“…[17,18] Again, the acidityd etermined is an averagep roperty of the bulk solutions. In the present work, we found that the excess spectrao ft he CNs tretching vibration could provide information on the microenvironments of solutions, [23,24] owing to the spectralresolution enhancement of excess spectroscopy, [25][26][27][28] ac oncept proposed in our laboratory. [19][20][21][22] Pelmenschikov et al, [19] used CD 3 CN as ap robe of Lewis and Brønsted acidityt od istinguish different adsorbing sites of zeolites.…”

“…Gai et al [21] introduced CNg roup into biological systems to detect changes on the local electrostatic fields of proteins. In the present work, we found that the excess spectrao ft he CNs tretching vibration could provide information on the microenvironments of solutions, [23,24] owing to the spectralresolution enhancement of excess spectroscopy, [25][26][27][28] ac oncept proposed in our laboratory.…”

Tracking the Micro‐Heterogeneity and Hydrogen‐Bonding Interactions in Hydroxyl‐Functionalized Ionic Liquid Solutions: A Combined Experimental and Computational Study

“…Besides, the positive peaks appearing at higher wavenumbers and the negative peaks appearing at lower wavenumbers can explain the blue shifts of ν(S=O) and ν(C−F) in Figure S2. According to literature, [23] the blue shifts mean that H‐bonding interactions involving S=O and C−F are getting stronger upon dilution. It is also found that the intensity of both positive and negative peaks increases with the addition of CD 3 CN until x (CD 3 CN)=0.6 and then decreases.…”

“…In another word, H-bonding interactions between CD 3 CN and [TFSI] À anion are stronger than those CD 3 CNÀ CD 3 CN interactions. [23] It can be seen from Figure 2(c) that with the increasing mole fraction of CD 3 CN, absorption peaks of ν as, i.p. (S=O), ν as, o.p.…”

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