Association structures of ionic liquid/DMSO mixtures studied by high-pressure infrared spectroscopy

Abstract

Using high-pressure infrared methods, we have investigated close interactions of charge-enhanced C-H-O type in ionic liquid∕dimethyl sulfoxide (DMSO) mixtures. The solvation and association of the 1-butyl-3-methylimidazolium tetrafluoroborate (BMI(+)BF(4)(-)) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMM(+)BF(4)(-)) in DMSO-d(6) were examined by analysis of C-H spectral features. Based on our concentration-dependent results, the imidazolium C-H groups are more sensitive sites for C-H-O than the alkyl C-H groups and the dominant imidazolium C-H species in dilute ionic liquid∕DMSO-d(6) should be assigned to the isolated (or dissociated) structures. As the dilute mixtures were compressed by high pressures, the loss in intensity of the bands attributed to the isolated structures was observed. In other words, high pressure can be used to perturb the association-dissociation equilibrium in the polar region. This result is remarkably different from what is revealed for the imidazolium C-H in the BMM(+)BF(4)(-)∕D(2)O mixtures. DFT-calculations are in agreement with our experimental results indicating that C(4)-H-O and C(5)-H-O interactions seem to play non-negligible roles for BMM(+)BF(4)(-)∕DMSO mixtures.

Local structures of ionic liquids in the presence of gold under high pressures

“…It is well known that high pressures almost invariably cause phase changes and the pure ionic liquids will most likely be frozen, i.e., in solid form. [27][28][29] The sharper structures revealed in Fig. 2(b) is in part due to the conformation drift and anisotropic environment in a solid structure.…”

“…Pressure calibration follows previous method. 28 The pressure dependence of screw moving distances was measured. Figure 2(a), two resolved absorption bands (3118 and 3157 cm −1 ) are observed with 1-ethyl-3-methylimidazolium cation.…”

“…The pressures used to investigate chemical systems typically range from ambient to several GPa; such pressures mainly change intermolecular distances and affect conformations. [27][28][29][30] Previous high-pressure measurements indicated that acetonitrile and dimethyl sulfoxide can be added to change the structural organization of ionic liquids. 27,28 Under ambient pressure, Raman spectra indicate that the more thermodynamically stable butyl structure of the cations is the gauche-anti (GA) and all-anti forms for [BMI][Br] and [BMI][Cl], respectively.…”

Structural Elucidation of the Binary Mixtures of [EMIM][BF4] and [BMIM][BF4] in Ethyl‐Substituted Solvents by Isothermal Titration Calorimeter

“…Further, quantum mechanical DFT calculations with the NMR spectroscopy have been used to determine the structural variations of the mixture of [EMIM][BF 4 ] and dichloromethane . The intermolecular interactions between the ionic liquids and DMSO were also analyzed by some researchers by using IR spectroscopy and measured the excess properties …”

Derivatização de celulose sob condições homogêneas: cinética e mecanismo de acilação do biopolímero em LiCI/DMAC e liquídos iônicos/solventes apróticos dipolares

“…The results of several experimental techniques, including FTIR, (Jiang et al 2011) conductivity ( We have also used conductivity in order to probe the IL-cellulose hydrogen bonding. As shown in Figures 4.11 and 4.12; in most cases, the dependence of (λ) on [IL] is linear; for the same IL concentration, the value of λ (IL/DAS) > λ (MCC-IL/DAS) , probably because the mobility of the free chloride ion of the IL is larger than that of the Cl -····H-O-AGU.…”