Binary Mixtures Of Ionic Liquids Research Articles

A binary mixture of ionic liquids as a sustainable electrocatalyst for oxygen evolution reaction

A binary mixture of ionic liquids (BmIL1) has been designed from [C12mim][Br] and [MPIM][HCOO] and used as a green and metal free electrocatalyst for oxygen evolution reaction (OER). BmIL1 was found to possess notable electrochemical stability in an alkaline medium to be used as an electrocatalyst in water splitting. Under alkaline conditions, the overpotential to achieve a current density of 10 mA/cm2 is 0.63 V and the Tafel slope is as small as 53.17 mV dec−1. The electrocatalyst can be stabilized over a glassy carbon electrode without adding any binder. To the best of our knowledge, this is the first report on designing an electrocatalyst for water splitting using ionic liquids without adding any binder. Moreover, the minimal E-factor, 100% atom economy and greater Eco Scale associated with the BmIL1 justifies the sustainable synthesis of the green electrocatalyst.

Efficient synthesis of cellulose acetate through one-step homogeneous acetylation of cotton cellulose in binary ionic liquids

Cellulose acetate (CA) is an important cellulose derivative with a wide range of applications. To adopt a more efficient and environmentally friendly method to synthesize cellulose acetate, a binary ionic liquid mixture of 1-butyl-3-methylimidazole chloride salt (BmimCl) and 1-butyl-3-methyldihydroimidazole phosphate (BmimH2PO4) was used. Compared to the conventional methods, this approach didn't require pre-activation of cellulose and the process of homogeneous acetylation proceeded without a catalyst. By simply adjusting the reaction conditions, cellulose acetate with a degree of substitution (DS) in the range of 0.83–3.0 was produced by one-step homogeneous acetylation without hydrolysis. Furthermore, the cellulose acetate film produced by solvent casting exhibited smooth surface characteristics, 95 % transparency, and 57.9 MPa tensile strength. Therefore, this study highlights the importance of using binary ionic liquid mixtures for facile synthesis of cellulose acetate. Due to their excellent transparency and mechanical properties, newly synthesized cellulose acetate films could replace commercial films.

Binary imidazolium based aqueous ionic liquid droplet on a rough surface: a molecular dynamics study

Ionic liquids (ILs) have garnered immense attention due to their tunable physicochemical properties. In this study, we delve into the wetting behaviour and interfacial properties of aqueous binary IL mixtures containing [EMIM] [BF4] and [HMIM] [BF4] on both smooth and rough graphite surfaces. Employing classical molecular dynamics simulations, we systematically explored the effects of IL concentration and surface morphology on wetting phenomena. To ensure the equilibrium of the systems, we began by calculating the interaction energies between the components. Subsequently, contact angles were computed, shedding light on the wetting characteristics of the aqueous binary IL mixtures. We meticulously examined the density profiles of the IL systems from the substrate to unravel the dominance of one IL over the other, exploiting the hydrophilic nature of [EMIM] [BF4] and the hydrophobic nature of [HMIM] [BF4]. A comprehensive analysis of hydrogen bond distribution allowed us to discern the intricate nature of these aqueous binary IL droplets. We probed the changes in intermolecular forces within the aqueous IL solution by investigating surface tensions. The tunability of these ILs emerges as a significant aspect of our study, paving the way for their tailored application in engineering and scientific domains. Schematic diagram showing the density distribution of hydrophilic and hydrophobic ILs ([EMIM] [BF4] and [HMIM] [BF4]) in water and also the hydrogen bond (HB) distribution of anion ([BF4]−) water inside the droplet on a pillared surface with a surface fraction ( f ) of 0.4 and pillar height of H = 4 .

Physicochemical and catalytic behavior of binary mixtures of n-alkyl imidazolium bromide ionic liquids with poly (ethylene glycol)-400: Application of flory statistical theory

In this work, Flory statistical theory is employed to predict the important physicochemical properties namely density, isothermal compressibility, internal pressure, coefficient of volume expansion, energy of vaporization, heat of vaporization, cohesive energy density, solubility parameter and polarity index for three binary mixtures of PEG-400 + [CnMim][Br], where n=4, 6, and 8 at different temperatures (T= 298.15 K, 308.15 K, and 318.15 K). Furthermore, the applicability of Flory statistical theory to predict certain physicochemical properties has been verified. Excess properties viz., excess enthalpy, excess Gibbs free energy, and excess entropy are also determined for these binary mixtures. The variation of energy of vaporization, heat of vaporization, solubility parameter and excess parameters are used to analyze the catalytic behavior and prevalent molecular interactions of these mixtures.

Physicochemical properties of binary mixtures of cation-fluorinated ionic liquids with their non-fluorinated analogues

This work reports an investigation of the physicochemical properties (density, viscosity, refractive index and thermal stability) of four binary mixtures having a common acetate ([OAc]¯), trifluoromethanesulfonate ([OTf]¯) or bis(trifluoromethylsulfonyl)imide ([NTf2]¯) anion with either cation-fluorinated and non-fluorinated methylimidazolium (MIm) or pyridinium (Py) cations respectively, at various temperatures. The mixing behaviour of the binary mixtures was analysed by 1H and 19F Nuclear magnetic resonance (NMR) spectrometry, and the excess properties of the mixtures were calculated from the physicochemical data. The binary mixtures of fluorinated ionic liquids (FILs) with their non-fluorinated or alkyl-substituted analogues (AILs) showed an increase in density and viscosity but a decrease in refractive index with an increase in mole fraction of the pure FILs. The thermal stability of the AILs was higher than the FILs, however, an increase in the mole fraction of the pure FILs in the binary mixtures made a negligible impact on the thermal stability of the binary mixtures. These binary mixtures were found to deviate from ideal behaviour for the different physicochemical properties tending to vary between the extremes of the pure components. The large differences in properties of FILs compared with their non-fluorinated analogues were shown to be associated with the size of the fluorine atoms in the fluoro-alkyl chain, the tendency of the fluoro-alkyl chain to form aggregates with fluorinated anions, and the hydrogen bond acceptor strength of the anions. The excess properties were fitted to the Redlich-Kister polynomial equation, and no significant deviation was obtained. This study shows that the physicochemical properties of the fluorinated ionic liquids can conveniently be adjusted for specific applications by simply varying the amount of the cation-fluorinated component in binary mixtures.

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study.

We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < XIL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

Estimation of Ultrasonic Velocity, Density, Internal Pressure, and Thermophysical Parameters of Ionic Liquid Mixtures: Application of Flory's Statistical Theory.

Flory's statistical theory (FST) has been employed to estimate the ultrasonic velocity, density, internal pressure, and several important thermophysical parameters such as the energy of vaporization, the heat of vaporization, cohesive energy density, polarity index, and solubility for eight binary mixtures of ionic liquids and water within the temperature range of 288.15 to 308.15 K. The ionic liquids chosen for this investigation are [BMim][dca], [BMim][TfO], [BMpy][TfO], [BMpyr][dca], [BMpyr][TfO], [EEPy][ESO4], [HMim][dca], and [MPy][MSO4]. The predicted values of ultrasonic velocity and density show good agreement with the data reported in the literature. It endorses the applicability of FST to these binary mixtures. A comparative analysis of the internal pressure values (Pi) determined by using FST and the standard thermodynamic approach is also presented. The results obtained for Pi using both approaches show good agreement. Besides, for the mixtures under study, the correlation between ultrasonic velocity, density, and surface tension has also been examined. The variation of thermophysical parameters with concentration and temperature changes has been utilized to explore the nature and strength of the solute-solvent interactions prevalent in these mixtures. It is pointed out that A-A-type interactions dominate over A-B-type interactions in water-rich regions of the mixtures.

Temperature dependence investigations of molecular interactions and excess thermodynamic parameters of binary mixtures of ionic liquids and water using Flory's statistical theory

AbstractFlory's Statistical Theory (FST) has been applied to investigate excess thermodynamical parameters viz., excess enthalpy, excess entropy, and excess Gibbs free energy for eight binary mixtures of ionic liquids and water at different concentration and temperatures. The concentration and temperature dependent variations of excess enthalpy suggest that ionic liquid mixtures exhibit an endothermic nature and the presence of weak dispersive forces among their constituents. The positive excess Gibbs free energy of mixing points out that the pure components do not mix thoroughly for the systems under study. Overall, these binary systems are thermodynamically unfavorable suggesting that the mixing of ionic liquids and water is not energetically favored or spontaneous. Experimental molar volumes are compared with those calculated using FST and these values show excellent agreement. It affirms the validity of FST's application to these systems. Additionally, some partial properties have also been determined to explore the solute‐solvent interactions. The Redlich‐Kister (R‐K) polynomial model has been applied to excess thermodynamical parameters The high R2 values and low standard deviation values confirm the validity of fitting the RK polynomial model to the functions obtained using FST of liquids for these systems within the given temperature range.

Viscosity of imidazolium ionic liquids and mixtures of ILs from entropy scaling using the PC-SAFT and ePC-SAFT equations of state

Entropy scaling is a promising method for the development of engineering models for transport properties of ionic liquids (ILs). Here we present two entropy scaling models for the viscosity of ionic liquids and their mixtures at various temperatures and pressures: 1) a molecular-based approach treating each IL as one pure species and using the PC-SAFT equation of state (EoS); and 2) treating each ion as a separate species and using the ePC-SAFT EoS. Both approaches were correlated to viscosity data of 12 ionic liquids from the imidazolium cation class and three different anions comprising 4233 data points with overall average absolute deviations (%AARDs) of less than 8 % over a wide range of temperature and pressures. The ion-based approach was better able to correlate IL viscosity at low temperatures and/or high pressure (to 4011 bar) than the molecular approach. The functional entropy-scaling coefficients for both models were regressed as linear functions of molecular weight, which allowed good prediction of another nine ionic liquids not in the training set. Interestingly, both approaches well predict the viscosity of binary mixtures of imidazolium ionic liquids. In addition, the effect of various reference viscosities and comparison with the Peng-Robinson EoS was performed.

Developing a two-grade model for the thermal conductivity of ionic liquids and their mixtures

Thermal conductivity (λ) is a crucial factor in the screening and design of ionic liquids (ILs) with desired thermal properties. Given the time consumption and computational inconvenience associated with structure-based models, a model grading strategy is proposed. This strategy aims to associate λ of ILs with their three reference properties separately in a two-grade model based on the kinetic theory and previous work. Subsequently, the model parameters are derived from the gathered database, and the prediction of λ is made with an average relative deviation (ARD) less than 5.78%. Further comparisons were conducted with the other three models, illustrating that our model exhibits high accuracy and is easily applicable, requiring only one of three reference properties. Finally, this model grading strategy is expanded to the determination of the thermal conductivity of binary mixtures (λm) of ILs without necessitating the individual λ values of each component. This approach accurately predicts the λm with an ARD less than 4.20%.

Ionic liquid binary mixtures: Machine learning‐assisted modeling, solvent tailoring, process design, and optimization

AbstractThis work conducts a comprehensive modeling study on the viscosity, density, heat capacity, and surface tension of ionic liquid (IL)‐IL binary mixtures by combining the group contribution (GC) method with three machine learning algorithms: artificial neural network, XGBoost, and LightGBM. A large number of experimental data from reliable open sources is exhaustively collected to train, validate, and test the proposed ML‐based GC models. Furthermore, the Shapley Additive Explanations technique is employed to quantify the influential factors behind all the studied properties. Finally, these ML‐based GC models are sequentially integrated into computer‐aided mixed solvent design, process design, and optimization through an industrial case study of recovering hydrogen from raw coke oven gas. Optimization results demonstrate their high computational efficiency and integrability in solvent and process design, while also highlighting the significant potential of IL‐IL binary mixtures in practical applications.

A state-of-the-art theoretical method for estimating ultrasonic velocity in ionic liquid mixtures: An extension of McAllister's interaction model

McAllister’s Interaction Model has been extended to predict ultrasonic velocities in eight binary mixtures of ionic liquids and water at temperatures T = 288.15 K, 298.15 K, and 308.15 K.The ionic liquids chosen for the current study are [BMim][TfO], [BMpyr][TfO], [BMpy][TfO], [BMim][dca], [HMim][dca], [BMpyr][dca], [Mpy][MSO4], and [EEpy][ESO4]. The interactions considered in present cases have been investigated for a range of variations from three-body interactions to nine-body interactions. The experimental values of ultrasonic velocities for all the mixturesat temperatures T = 288.15 K, 298.15 K, and 308.15 Kare compared with the computed values. The differences between the experimental and theoretically predicted velocities are determined in terms of absolute percentage deviation. It is worth mentioning that McAllister’s Model of interactions has been extended, for consideration, from three-body interactions to nine-body interactions among constituent molecules of binary mixtures and applied for the prediction of ultrasonic velocities in binary mixtures of water and ionic liquids for the first time. The extended Huckel theory (EHT) is used to calculate the charge distributions in eight ionic liquids and water molecules to understand the active sites available for interactions on each constituting molecule of the binary mixtures under investigation. The results we obtained complemented our decision to extend McAllister’s interactions model (MAIM) to higher orders (four-body to nine-body interactions). The results obtained (using extended MAIM) report an excellent agreement with experimental velocity values for nine-body interactions for all the systems under study. It is also pointed out that McAllister’s assumption that the free energies of activation are the additive quantity for viscosity investigation in organic liquid mixtures is also valid in the case of ultrasonic velocity studies for ionic liquids and water mixtures. Considering McAllister’s conjecture that rather than a planar system of interactions among solvent-solute molecules, a three-dimensional approach to intermolecular interactions can be more appropriate, authors have confirmed the validity of McAlliter’s conjecture by successfully investigating three-dimensional multi-body (in the present case: 9-body) interactions in the binary mixtures of ionic liquids and water.

Study on association and thermal stability of binary imidazolium ionic liquid mixtures

Ionic liquid (IL) mixtures with specific properties can be designed by the combination of different ionic liquids (ILs), but there are few studies on the physicochemical properties of IL mixtures with different ratios. Thus, this work explores the association and thermal stability of binary imidazolium IL mixtures. In particular, the physicochemical properties of binary IL mixtures at different ratios were investigated. Four different ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-butyl-3-methylimidazolium nitrate ([BMIM][NO3]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), and 1-butyl-3-methyl-imidazolium trifluoroacetate ([BMIM][CF3COO]), were selected as the parent salts to form the different binary imidazolium IL mixtures. These IL mixtures were tested at different temperatures (25, 30, 35, 40, 45, and 50 °C) and ratios (1:9, 3:7, 5:5, 7:3, and 9:1) by viscometer, conductivity meter, and then by isothermal thermogravimetric analysis in the temperature rise range of 30–500 °C. It was found that the increase in temperature decreased the association of IL mixtures, thus destroying the association behavior between the parent salts. Accordingly, different ratios of the parent salts had no significant effect on the thermal stability of some IL mixtures. Moreover, the results showed that smaller anions were more likely to combine with cations to form ion clusters or ion pairs, enhancing the association of binary IL mixtures. Thus, it increased the thermal stability of IL mixtures.

Experimental and in silico insights: interaction of dimethyl sulphoxide with 1-hexyl-2-methyl imidazolium bromide/1-octyl-2-methyl imidazolium bromide at different temperatures.

Ionic liquids have gained attention as 'designer solvents' since they offer a broad spectrum of properties that can be tuned by altering the constituent ions. In this work, 1-alkyl-2-methyl imidazolium-based ionic liquids with two different alkyl chains (alkyl = hexyl and octyl) have been synthesized and characterized. Since the binary mixture of ionic liquids with molecular solvents can give rise to striking physicochemical properties, the interaction of the synthesized room temperature ionic liquids, 1-hexyl-2-methyl imidazolium bromide [HMIM][Br]/1-octyl-2-methyl imidazolium bromide [OMIM][Br] with DMSO has been examined through density and specific conductance at T = (303.15, 308.15, 313.15 and 318.15) K under atmospheric pressure. The obtained molar volume and excess molar volume are fitted to the Redlich-Kister polynomial equation, and the standard deviation is noted. The positive excess molar volume at elevated temperatures indicates volume expansion due to the mutual loss of dipolar association and differences in the sizes and shapes of the constituent molecules. To have a better understanding of the reactivity and efficacy of 1-hexyl-2-methyl imidazolium bromide and 1-octyl-2-methyl imidazolium bromide with DMSO, the Becke, 3-parameter, Lee-Yang-Parr (B3LYP) correlation function of density functional theory (DFT) has been used. The ORCA Program version 4.0 calculates the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy. The effective reactivities of both the compounds that showed an energy band gap (ΔE), i.e., the difference between ELUMO and EHOMO, are 7.147 and 8.037 kcal mol-1.

Extraction of Pyrrole from Its Mixture with n-Hexadecane Using Ionic Liquids and Their Binary Mixtures.

The conventional hydrodenitrogenation method is expensive and involves the use of catalysts and harsh procedures. In the last few years, ionic liquids (ILs) have gained attention as a promising alternative solvent for fuel oil extractive denitrogenation. In this work, the Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to screen 173 potential ILs as solvents for fuel oil. Two ILs (1-ethyl-3-methylimidazolium dicyanamide ([EMIM][N(CN)2]) and 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO3])) were selected for experimental investigation. The experimental liquid-liquid extraction of pyrrole (taken as the model nitrogen compound) from n-hexadecane (the model fuel) was conducted at 298 K and 1 atm with feed concentrations of pyrrole ranging from 10 to 50 wt%, using either the two pure ILs or their mixtures with dimethylformamide or ethylene glycol. Moreover, the NRTL model was effectively used to correlate the experimental tie lines. This work shows that the use of a binary mixture of ILs with a conventional solvent results in good selectivity, but has a low capacity for extracting pyrrole compounds. On the other hand, using an IL-IL mixture exhibits good results for both capacity and selectivity. All the ternary systems tested showed positive slopes, indicating that the nitrogen compounds had a higher affinity for the IL and binary mixture extract phase. In fact, the extraction efficiency for all the systems shows promising results. This characteristic is advantageous, as it requires less solvent to remove nitrogen compounds.

Synthesis of new imidazole-based ionic liquids with antifungal activity against Candida albicans.

Candida albicans cause a problematic condition in immunocompromised patients that could not be treated quickly due to the resistant behavior of microorganisms. This study aimed to investigate the effect of a novel ionic liquid (IL) as a new drug on C. albicans strains. Seven newly binary ionic liquids mixtures were synthesized, and among them, ([prollinium chloride] [1-methylimidazolium 3-sulfonate] ([pro-HCl][MImS]) was selected and characterized by 1HNMR, 13C NMR, and FT-IR methods. Samples from patients (n=50) with candidiasis were collected and identified through culture media. ERG11 gene overexpression was related to resistance against azole-bearing drugs. The antibiogram, well diffusion assay, MICs, and MFCs tests were operated. PCR and Real-time evaluated the expression of the ERG11 gene, and the rate of cell death was detected using Flow Cytometry. Our data manifested that this novel IL (Ionic Liquid) can inhibit C. albican's growth, reduce the expression of ERG11 and increase dead cells. The newly synthesized IL had an inhibiting effect on the growth of the C. albicans strains and may be used as an alternative candidate for novel drug design.

Prediction of Refractive Indices of Binary Mixtures of Ionic Liquids and Water

In the present work, we have successfully predicted the refractive indices of binary mixtures containing ionic liquids (ILs) and water as a component following the approach of Gladstone–Dale and Newton. These approaches were proposed as adequate to predict the refractive indices of mixtures containing imidazolium-based ILs with water or ethanol. It requires just the knowledge of the density and refractive index of pure components to obtain the value of refractive index of binary mixtures at any composition. We have selected 30 binary systems that contain ILs from imidazolium, ammonium, pyrrolidinium, and pyridinium families for validation. The tested data comprise of more than 400 mixture points. The results are presented in terms of average percentage deviations (APDs) from the experimental values. The Gladstone–Dale method gives better results compared to the Newton approach. The reasons why these approaches give large APDs for some mixtures are discussed in the manuscript.

Effect of cation size of binary cation ionic liquid mixtures on capacitive energy storage

Ionic liquid mixtures show promise as electrolytes for supercapacitors with nanoporous electrodes. Herein, we investigate theoretically and with experiments how binary electrolytes comprising a common anion and two types of differently-sized cations affect capacitive energy storage. We find that such electrolytes can enhance the capacitance of single nanopores and nanoporous electrodes under potential differences negative relative to the potential of zero charge. For a two-electrode cell, however, they are beneficial only at low and intermediate cell voltages, while a neat ionic liquid performs better at higher voltages. We reveal subtle effects of how the distribution of pores accessible to different types of ions correlates with charge storage and suggest approaches to increase capacitance and stored energy density with ionic liquid mixtures.

A combined experimental and theoretical study on the structures, dynamics and interactions of BMIMTfO and BMIMTFSI binary ionic liquid mixtures

The study of ionic liquid mixtures has garnered growing attention due to its importance. However, our current understanding of molecular interactions in ionic liquid mixtures remains incomplete, necessitating further research to expand the foundational knowledge in this field. In this work, a comprehensive approach incorporating theoretical calculations and diverse experimental techniques was utilized to research the structures, dynamics, and interactions of 1-butyl-3-methylimidazolium trifluoromethansulfonate (BMIMTfO) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (BMIMTFSI) mixtures. The obtained conclusions are as follows: (1) The primary interaction sites for [BMIM]+, [TfO]− and [TFSI]− were identified as the C2H, O atoms of SO3 and O atoms of SO, respectively. (2) With the addition of BMIMTFSI, the hydrogen bonding interactions associated with imidazolium CH are weakened, while those associated with alkyl CH and SO are strengthened. Additionally, there is an increased propensity for aggregation between the two anions ([TfO]−, [TFSI]−) and [BMIM]+. (3) The interactions between [BMIM]+ and [TfO]− are stronger compared to those between [BMIM]+ and [TFSI]−, and the self-diffusion coefficient followed the order of [BMIM]+ > [TFSI]− > [TfO]−. (4) The 2[BMIM]+[TfO]−, 2[BMIM]+[TFSI]−-[TfO]−, 2[BMIM]+[TFSI]− and 2[BMIM]+[TfO]−-[TFSI]− complexes were assigned using excess spectroscopy and quantum chemical calculations.

Hydrogen-Bonded Complexes in Binary Mixture of Imidazolium-Based Ionic Liquids with Organic Solvents.

Though local structures in ionic liquids are dominated by strong Coulomb forces, directional hydrogen bonds can also influence the physicochemical properties of imidazolium-based ionic liquids. In particular, the C-2 position of the imidazolium cation is acidic and can bind with suitable hydrogen bond acceptor sites of molecular solvents dissolved in imidazolium-based ionic liquids. In this report, we identify hydrogen-bonded microenvironments of the model ionic liquid, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate, and the changes that occur when molecular solvents are dissolved in it by using a C-D infrared reporter at the C-2 position of the cation. Our linear and nonlinear infrared experiments, along with computational studies, indicate that the molecular solvent dimethyl sulfoxide can form strong hydrogen-bonded dimers with the cation of the ionic liquid at the C-2 position. In contrast, acetone, which is also a hydrogen bond acceptor similar to dimethyl sulfoxide, does not show evidence of cation-solvent hydrogen-bonded conformers at the C-2 position. The outcome of our study on a broad scale strengthens the importance of cation-solute interactions in ionic liquids.