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Ionic liquids (ILs) are ionic compounds with low melting points that can be designed to be used in an extensive set of commercial and industrial applications. However, the design of ILs is limited by the quantity and quality of the available data in the literature; therefore, the estimation of physicochemical properties of ILs by computational methods is a promising way of solving this problem, since it provides approximations of the real values, resulting in savings in both time and money. We studied two data sets of 281 and 134 liquids based on the molecule imidazole that were analyzed with QSPR techniques. This paper presents a software architecture that uses clustering techniques to improve the robustness of estimation models of the melting point of ILs. These results indicate an error of 6.25% in the previously unmodeled data set and an error of 4.43% in the second data set. We have an improvement with the second data set of 1.81% over the last results previously found.

During the manufacturing of pharmaceutical compounds, solvent mixtures are commonly used, where the addition of a cosolvent allows for the tuning of the intermolecular interactions present in the system. Here we demonstrate how a similar effect can be accomplished using a room temperature ionic liquid. The pharmaceutical compound acetaminophen is studied in 21 common ionic liquids composed of a 1-n-alkyl-3-methylimidazolium cation with 1 of 7 anions. Using the acetate anion, we predict a large enhancement in solubility of acetaminophen relative to water. We show how this is caused by a synergistic effect of favorable interactions between the ionic liquid and the phenyl, hydroxyl and amide groups of acetaminophen, demonstrating how the ionic liquid cation and anion may be chosen to preferentially solvate different functional groups of complex pharmaceutical compounds. Additionally, while the use of charge scaling in ionic liquid force fields has previously been found to have a minute effect on ionic liquid structural properties, we find it appreciably affects the computed solvation free energy of acetaminophen, which in turn affects the predicted solubility.

We demonstrate a controllable doping technique of few-layer black phosphorus (BP) via surface charge transfer using an ionic liquid mixture of EMIM(C6H11N2+):TFSI(C2F6NO4S2-) [EMIM:TFSI, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide]. A wide range of hole carrier densities, from 1011 cm-2 (nondegenerate) to 1013 cm-2 (degenerate), can be obtained by controlling the weight percentage of the ionic liquid mixture. The doping method we proposed in this paper can be applied to make a multifunctional homogeneous lateral p-n junction device. By doping a fraction of the BP sample and by applying a gate voltage to the other fraction of the BP, we obtain homogeneous lateral p+-p, p+-n, p+-n+ junction diodes in a single BP channel. The homogeneous lateral BP p+-p and p+-n junctions display ideal rectifying behavior and a much stronger photoresponse due to the built-in potential. Furthermore, at high positive gate voltages, the interband tunneling enables the homogeneous lateral p+-n+ junction transistors to provide both a negative differential resistance (NDR) and a negative transconductance (NTC) in the current-voltage characteristics at room temperature. On the basis of our results, it is possible to build novel devices utilizing the large NDR and NTC in BP such as amplifiers, oscillators, and multivalued logic systems. [ABSTRACT FROM AUTHOR]

This paper presents the computational assessment of the electrochemical stability of a series of alkyl methylimidazolium-based ionic liquids for their use as lithium battery electrolytes. The oxidation and reduction potentials of the constituent cation and anion of each ionic liquid with respect to a Li+/Li reference electrode were calculated using density functional theory following the method of thermodynamic cycles, and the electrochemical stability windows (ESW)s of these ionic liquids were obtained. The effect of varying the length of alkyl side chains of the methylimidazolium-based cations on the redox potentials and ESWs was investigated. The results show that the limits of the ESWs of these methylimidazolium-based ionic liquids are defined by the oxidation potential of the anions and the reduction potential of alkyl-methylimidazolium cations. Moreover, ionic liquids with [PF6]- anion have a wider ESW. In addition to characterizing structure-function relationships, the accuracy of the computational approach was assessed through comparisons of the data against experimental measurements of ESWs. The potentials calculated by the thermodynamic cycle method are in good agreement with the experimental data while the HOMO/LUMO method overestimates the redox potentials. This work demonstrates that these approaches can provide guidance in selecting ionic liquid electrolytes when designing high-voltage rechargeable batteries. [ABSTRACT FROM AUTHOR]

Description of the local microscopic structure in ionic liquids (ILs) is a prerequisite to obtain a comprehensive understanding of the influence of the nature of ions on the properties of ILs. The local structure is mainly determined by the spatial arrangement of the nearest neighboring ions. Therefore, the main interaction patterns in ILs, such as cation-anion H-bond-like motifs, cation-cation alkyl tail aggregation, and ring stacking, were considered within the framework of the nearest-neighbor approach with respect to each particular interaction site. We employed classical molecular dynamics (MD) simulations to study in detail the spatial, radial, and orientational relative distribution of ions in a set of imidazolium-based ILs, in which the 1-butyl-3-methylimidazolium (C4mim+) cation is coupled with the acetate (OAc-), chloride (Cl-), tetrafluoroborate (BF4 -), hexafluorophosphate (PF6 -), trifluoromethanesulfonate (TfO-), or bis(trifluoromethanesulfonyl)amide (TFSA-) anion. It was established that several structural properties are strongly anion-specific, while some can be treated as universally applicable to ILs, regardless of the nature of the anion. Namely, strongly basic anions, such as OAc- and Cl-, prefer to be located in the imidazolium ring plane next to the C-H2/4-5 sites. By contrast, the other four bulky and weakly coordinating anions tend to occupy positions above/below the plane. Similarly, the H-bond-like interactions involving the H² site are found to be particularly enhanced in comparison with the ones at H4-5 in the case of asymmetric and/or more basic anions (C4mimOAc, C4mimCl, C4mimTfO, and C4mimTFSA), in accordance with recent spectroscopic and theoretical findings. Other IL-specific details related to the multiple H-bond-like binding and cation stacking issues are also discussed in this paper. The secondary H-bonding of anions with the alkyl hydrogen atoms of cations as well as the cation-cation alkyl chain aggregation turned out to be poorly sensitive to the nature of the anion. [ABSTRACT FROM AUTHOR]

This paper reports the thermodynamicinhibition effect of sevenionic liquids (ILs) on methane hydrate formation. The isochoric multistepheating dissociation pressure search method is applied for experimentallydetermining the phase boundary between hydrate–liquid–vapor(H–L–V) phases and liquid–vapor (L–V)phases in the pressure and temperature ranges of 3.45–13.28MPa and 274.3–287.6 K, respectively. All the studied IL aqueoussolutions are used at a mass fraction of 0.1. A comparison of thethermodynamic inhibitory performance of various ILs is carried outand reveals the predominant role of the type of anion of ILs. Consideringthe difficulty in directly measuring the dissociation enthalpies,the values of ΔHof methane hydrate are alsocalculated using the Clausius–Clapeyron equation. It is foundthat the mean dissociation enthalpies of methane hydrate in the presenceof the seven ILs vary from 59.05 to 60.81 kJ·mol–1, and are very close to that in pure water. [ABSTRACT FROM AUTHOR]

In this paper, we present the resultsfrom molecular dynamics simulationsof the equilibrium properties of liquid/liquid interfaces of roomtemperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]) and simple alcohols (i.e., methanol, 1-butanol,and 1-hexanol) at room temperature. Polarizable potential models areemployed to describe the interactions among species. Results fromour simulations show stable interfaces between the ionic liquid and n-alcohols, and we found that the interfacial widths decreasefrom methanol to 1-butanol systems and then increase for 1-hexanolinterfaces. Angular distribution analysis reveals that the interfaceinduces a strong orientational order of [bmim] and n-alcohol molecules near the interface, with [bmim] extending itsbutyl group into the alcohol phase, whereas the alcohol has the OHgroup pointing into the ionic liquid region, which is consistent withthe recent sum-frequency-generation experiments. We found the interfaceto have a significant influence on the dynamics of ionic liquids and n-alcohols. The orientational autocorrelation functionsillustrate that [bmim] rotates more freely near the interface thanin the bulk, whereas the rotation of n-alcohol ishindered at the interface. Additionally, the time scale associatedwith the diffusion along the interfacial direction is found to befaster for [bmim] but slowed down for n-alcoholsapproaching the interface. We also calculate the dipole moment of n-alcohols as a function of the distance normal to the interface.We found that, even though methanol and 1-butanol have different dipolemoments in bulk phase, they reach a similar value at the interface. [ABSTRACT FROM AUTHOR]