Imidazolium-based Imidazolium-based Ionic Liquids Research Articles

Extraction of Dibenzyl Disulfide from Transformer Oils by Acidic Ionic Liquid.

In recent years, dibenzyl disulfide (DBDS) in transformer oils has caused many transformer failures around the world, and its removal has attracted more attention. In this work, nine imidazolium-based ionic liquids (ILs) were applied as effective, green desulfurization extractants for DBDS-containing transformer oil for the first time. The results show that the desulfurization ability of the ILs for DBDS followed the order of [BMIM]FeCl4 > [BMIM]N(CN)2 > [BMIM]SCN > [BMIM](C4H9O)2PO2 > [BMIM]MeSO4 > [BMIM]NTf2 > [BMIM]OTf > [BMIM]PF6 > [BMIM]BF4. Especially, [BMIM]FeCl4 ionic liquid had excellent removal efficiency for DBDS, with its S partition coefficient KN (S) being up to 2642, which was much higher than the other eight imidazolium-based ILs. Moreover, the extractive performance of [BMIM]FeCl4 increased with an increasing molar ratio of FeCl3 to [BMIM]Cl, which was attributed to its Lewis acidity and fluidity. [BMIM]FeCl4 ionic liquid could also avail in the desulfurization of diphenyl sulfide (DPS) from model oils. The experimental results demonstrate that π-π action, π-complexation, and Lewis acid-base interaction played important roles in the desulfurization process. Finally, the ([BMIM]FeCl4) ionic liquid could be recycled five times without a significant decrease in extractive ability.

Unraveling hydrogen bond interactions between ketoconazole and imidazolium-based ionic liquids: An experimental and theoretical study

The solubility and solvation mechanism of the Biopharmaceutical Classification System class II insoluble drug, ketoconazole (KCZ), were investigated in eight different types of imidazolium-based ionic liquids (ILs). An in vitro cytotoxicity test was conducted on Human immortalized keratinocytes cells to evaluate the potential toxicity of these ILs. The results showed no cytotoxicity for any of the imidazolium-based ILs tested. The solubility of KCZ was then examined in the eight imidazolium-based ILs at temperatures ranging from 298.15 K to 338.15 K. The findings revealed that the solubility of KCZ followed a specific order among the imidazolium-based ILs tested. The imidazolium-based IL [BMIM][Tf2N] exhibited the highest solubility of KCZ, followed by [HMIM][PF6], [EMIM][Tf2N], [BMIM][TfO], [BMIM][PF6], [EMIM][TfO], [BMIM][BF4], and [EMIM][BF4] in decreasing order. To understand the interaction mechanism between the imidazolium-based ILs and KCZ, the cations, anions and KCZ were analyzed using σ-profiles computed from both the COSMO-RS model and quantum chemical calculations. The results indicated that KCZ had strong hydrogen bond (HB) acceptors, particularly the oxygen atom of the carbonyl group and the nitrogen atom of the imidazole ring. These HB acceptors contributed to the formation of stronger HBs with the hydrogen atoms of cations compared to the oxygen atoms of the anions. The trend of HB strength followed [Emim]+ > [Bmim]+ > [Hmim]+ > [Tf2N]− > [TfO]− > [PF6]− > [BF4]−. Based on these findings, it can be concluded that [BMIM][Tf2N], which has a strong HB donor cation and a strong HB acceptor anion, displayed the most effective dissolution of KCZ.

Adsorption behavior of vanadium(V) by supported imidazolium-based difunctionalized ionic liquid

This study reports the functionalization of imidazolium-based ionic liquids (ILs) anions to synthesize novel supported imidazolium-based difunctionalized ILs (SIBD-ILs). Polystyrene [1-butyl-3-methylimidazolium][bis(2-ethylhexyl)phosphate] (PS[C4mim][D2EHP]) was used as an adsorbent to separate and enrich vanadium from vanadium-containing solutions. The effects of parameters such as the initial pH, liquid-solid ratio (L/S), reaction time, and reaction temperature on V(V) adsorption behavior were investigated. The adsorption capacity of 283.63 mg/g was reached under optimal conditions. V(V) adsorbed on PS[C4mim][D2EHP] was effectively desorbed using 3 mol/L NaOH solution and regenerated PS[C4mim][D2EHP]. After 10 adsorption-desorption cycles, the adsorption capacity was maintained at 95.36% of the initial value. The selective adsorption property of PS[C4mim][D2EHP] was studied in vanadium solutions containing Fe(III) and Al(III) ions. At pH = 2.0, the separation coefficients of towards Fe(III) and Al(III) were the highest, 62.05 and 38.69, respectively. The adsorption process of PS[C4mim][D2EHP] for V(V) conformed to Freundlich and pseudo-second-order kinetic models. SIBD-ILs were characterized by Fourier transform infrared, X-ray Photoelectron Spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that PS[C4mim][D2EHP] was successfully prepared, and PS[C4mim][D2EHP] mainly adsorbed vanadium by ion association.

N-Heterocyclic Carbene Formation in the Ionic Liquid [EMIM+][OAc-]: Elucidating Solvation Effects with Reactive Molecular Dynamics Simulations.

Recent experimental and theoretical work has debated whether N-heterocyclic carbenes (NHCs) are natively present in imidazolium-based ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium acetate ([EMIM+][OAc-]) at room temperature. Because NHCs are powerful catalysts, determining their presence within imidazolium-based ILs is important, but experimental characterization is difficult due to the transient nature of the carbene species. Because the carbene formation reaction involves acid-base neutralization of two ions, ion solvation will largely dominate the reaction free energy and thus must be considered in any quantum chemical investigation of the reaction. To computationally study the NHC formation reaction, we develop physics-based, neural network reactive force fields to enable free energy calculations for the reaction in bulk [EMIM+][OAc-]. Our force field explicitly captures the formation of NHC and acetic acid by deprotonation of a EMIM+ molecule by acetate and in addition describes the dimerization of acetic acid and acetate. Using umbrella sampling, we compute reaction free energy profiles within the bulk IL and at the liquid/vapor interface to understand the influence of the environment on ion solvation and reaction free energies. Compared to reaction of the EMIM+/OAc- dimer in the gas phase, the bulk environment destabilizes formation of the NHC as expected due to the large ion solvation energies. Our simulations reveal a preference for the product acetic acid to share its proton with an acetate in solution and at the interface. We predict NHC content in bulk [EMIM+][OAc-] to be on the order of parts-per-million (ppm) levels, with order-of-magnitude enhancement of NHC concentration at the liquid/vapor interface. The interfacial enhancement of NHC content is due to both poorer solvation of the ionic reactants and solvophobic stabilization of the neutral NHC molecule at the liquid/vapor interface.

Insight into the stabilization mechanism of imidazole-based ionic liquids at the interface of the carbon nanotubes: A computational study

Ab initio calculations have been performed to systematically investigate the structures, binding energies, vibrational spectra, as well as the non-covalent interactions of imidazolium-based ionic liquids (ILs) at the interface of carbon nanotubes (CNTs). The effects of alkyl length of imidazolium cations, types of anions as well as diameters of CNTs on the relevant interfacial structures and properties have been explored in this study. Our calculations demonstrated that the interfacial imidazolium cations display two different orientations (cations paralleling and perpendicular to the CNTs surface) irrespective of the alkyl chain length of cations, types of anions and the diameters of CNTs. By comparison with the calculated binding energies between cations and the CNTs, the cations paralleling to the CNTs surface are thermodynamically much more stable due to the significant interfacial π-π stacking interactions. In addition, our results indicated that there is significantly difference for the infrared (IR) spectra of the imidazolium cations (between two orientations) on the CNTs surface. Therefore, with the IR spectra, the specific orientations of imidazolium cations on surface of CNTs can be better understood. Moreover, interaction region indicator (IRI) as well as symmetry-adapted perturbation theory (SAPT) analysis were employed to deep understanding of the non-covalent interactions between imidazolium-based ILs and CNTs. Our calculations explore that the paralleling cations is stabilized on the CNTs surface by the dispersion (especially for the π-π stacking) interactions. However, for the cations perpendicular to the CNTs surface, electrostatic, induction as well as the dispersion interactions are all very important. Our calculated results provide a molecular level understanding the stabilization mechanism of imidazole-based ILs at the interface of the CNTs and will be a bit favorable to clarify the existing debate on the stabilization mechanism from various experimental observations.

A novel molecular structure-based model for prediction of CO2 equilibrium absorption in blended imidazolium-based ionic liquids

• A comprehensive dataset including 4397 data points of CO 2 equilibrium solubility in imidazolium-based ionic liquids was acquired. • Various blended of imidazolium-based ILs were characterized based on their molecular frameworks. • Three machine learning predictive models were proposed to predict CO 2 solubility. • The simple but effective FFNN model gives reliable predictions, as compared with RBFNN and SVM algorithms. The present study highlights a comprehensive database including 4397 data points of CO 2 equilibrium solubility measurements in the 43 different imidazolium-based ionic liquids (ILs) over a broad range of pressures and absorption temperatures. The relation between the equilibrium CO 2 solubility and the molecular structure of the imidazolium-based ILs mixed with different kinds of solvents, including Diethanolamine (DEA), Methyl diethanolamine (MDEA), Diisopropylamine (DIPA), Amionomethyl propanol (AMP), and the equilibrium absorption pressure and the temperature has been accurately correlated. According to this database, a novel chemoinformatics-based descriptor model with a large number of 26 input data of structural information of all involved cation and anions and experimental conditions has been extracted. Three different machine learning methods, namely feed-forward neural network (FFNN), radial-based function neural network (RBFNN), and support vector machine (SVM), are employed to develop the derived descriptor-based model. The results of the three machine learning methods demonstrate that the prediction performance of the suggested models is quite reliable. Comparing the results indicate that the FFNN with corresponding values of RMSE = 0.071, R 2 = 0.952, and MAPE = 0.544 is the best paradigm to predict the CO 2 equilibrium solubility in imidazolium-based ILs.

On the Behavior of Newly Synthesized Functionalized Imidazolium-Based Ionic Liquids for Highly Efficient Extraction and Separation of Pirimicarb from Orchard Real Wastewater

The presence of pirimicarb compounds as pollutants in orchard wastewater has sparked rising worries about their detrimental impacts on the ecosystem and human health, and their removal is critical for Pakistan’s aquatic environment. It not only contaminates fruit, but it also leaches into the soil and contaminates groundwater. However, there is little data on the effective removal of pirimicarb from orchard wastewater. The main purpose of this study is to create a novel family of functionalized imidazolium-based ionic liquids (ILs) using a simple chemical process, which will be utilized for the first time to extract pirimicarb from orchard wastewater in an efficient, cost-effective, and environmentally acceptable manner. FTIR, SEM, XRD, TGA, BET, and 1H NMR spectroscopy were used to characterize the functionalized samples. The impact of the IL substituent on the separation capacity was studied. In addition, the extraction and separation of pirimicarb from orchard wastewater were investigated under a variety of conditions (time, concentration, and temperature) in order to better understand the adsorption behaviors of distinct ILs in an aqueous solution. The adsorption equilibrium was reached in 30 minutes, and the maximum removal of pirimicarb was achieved utilizing the synthesized [C2im][C3H6NH2]Br-, according to the data. The pseudo-first-order model and the Langmuir model both suit well with the adsorption mechanism of pirimicarb with very good adsorptive capacities. Thermodynamic analyses indicated spontaneous, endothermic, and entropy-driven adsorption processes. The synthesized imidazolium-based ILs have good regeneration capability and recycling at least for six adsorption-desorption runs and have also been used to successfully detect pirimicarb orchard wastewater samples. The superior safety of the proposed method nominates it as a promising future strategy for pollution prevention. Consequently, this work has proven that the pirimicarb adsorption to various imidazolium-based ILs was dependent on the structures of the produced imidazolium-based ILs, which specifies its potential for practical applications in water pollutant removal and environmental remediation.

Mineral composition and growth of tomato and cucumber affected by imidazolium-based ionic liquids

Imidazolium-based ionic liquids (ILs) have unique and tunable features with high potential in industrial use. However, the utilization of the ILs in industrial processes has recently arisen the question of their disposal and the effect on the environment. Therefore, in the present study, we investigated the effect of two commercial imidazolium-based ILs, 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]) on the growth and chemical composition of widely grown vegetables - tomato and cucumber. Different concentrations (10, 100 or 1000 mg L−1) of [Bmim][Cl] and [Dmim][Cl] were applied to the soil on which tomato was cultivated. After the harvest of tomato fruits, the same soil was used to grow and analyze the growth and chemical composition of cucumber. ILs significantly reduced shoot biomass and yield of tomato and significantly changed concentrations of N, K, Ca, Fe and Mn in the leaves, whereas concentrations of P, Cu and Zn were at the level of respected controls. The number of fruits of cucumber, grown on the soil previously treated with ILs, was significantly reduced along with yield, and mineral composition of leaves was significantly altered, with the exception to Cu. [Dmim][Cl] in general affected both tomato and cucumber more than [Bmim][Cl]. The application of IL with a longer alkyl substituent ([Dmim][Cl]) increased the temperature inside the tomato canopy and accelerated the senescence of plants.

Quasi-Universal Solubility Behavior of Light Gases in Imidazolium-Based Ionic Liquids with Varying Anions: A Molecular Dynamics Simulation Study.

In this work, the temperature-dependent solvation behavior of a number of important light gases, such as carbon dioxide, xenon, krypton, argon, oxygen, methane, nitrogen, neon, and hydrogen, in two important imidazolium-based ionic liquids (ILs) of the type 1-n-alkyl-3-methylimidazolium hexafluorophosphate ([Cnmim][PF6]) and 1-n-alkyl-3-methylimidazolium tetrafluoroborate ([CnmimBF4]) with varying chain lengths (n = 2, 4, 6, and 8) are investigated using molecular dynamics simulations for a temperature range between 300 and 500 K at a pressure of 1 bar. The aim of this work is first to propose a reliable estimate for the temperature-dependent solubility behavior of (very) light gases, e.g., hydrogen and nitrogen, where reported experimental data are inconsistent. Moreover, we would like to rationalize the common features of the temperature-dependent solvation of light gases for various imidazolium-based ionic liquids. For the selected solute gases in our simulated imidazolium-based ILs, we applied the potential distribution theorem using both Bennet's overlapping distribution method (ODM) and Widom's particle insertion technique to determine the temperature-dependent solvation free energies with good statistical accuracy. We observed from the simulations that the quantity of the solvation free energy of a gas molecule and its temperature derivatives are connected in regard to each other at a chosen reference temperature. This trend was observed for all the studied light gases. Moreover, the computed solvation enthalpies of all gases obey an enthalpy-entropy compensation behavior, which is almost identical for all the studied ILs. Based on this observation, we report a correlation between the temperature-dependent solubility behavior of light gases in various ILs at their reference state so that we are now able to semiquantitively predict the temperature-dependent solubility behavior of a certain gas in various imidazolium-based ionic liquids based on a single solubility value of that gas in one of the ILs at a certain temperature.

Wetting behavior of aqueous 1-alkyl-3-methylimidazolium tetrafluoroborate {[Cn MIM][BF4] (n = 2, 4, 6)} on graphite surface

Herein, molecular dynamics simulations have been conducted to investigate the effect of cation chain length on the wetting and interfacial properties of aqueous imidazolium-based ionic liquids (ILs) consisting of 1-ethyl-3-methylimidazolium [EMIM], 1-butyl-3-methylimidazolium [BMIM], and 1-hexyl-3-methylimidazolium [HMIM] cations with common tetrafluoroborate [BF4] anions on a graphite surface in the IL concentration range of 10–50 wt%. The difference between the contact angles of aqueous [EMIM][BF4] and [BMIM][BF4] droplets is very small regardless of the IL content. However, a noticeable reduction in the contact angle is observed for the IL with a longer alkyl chain [HMIM][BF4] at high IL concentrations. Furthermore, interfacial tensions and works of adhesion are calculated to quantify the wettability of the studied ILs; as a result, lower works of adhesion are obtained for the longer alkyl chain compounds (Sali et al., 2017). Droplet characteristics near the surface are obtained from two-dimensional density contours and orientation order parameters. The majority of IL molecules are located near the solid–liquid interface in all the studied cases. However, the [BMIM][BF4] and [HMIM][BF4] ILs with longer alkyl chains are also detected at the liquid–vapor interface. Finally, IL interactions with water molecules through hydrogen bonding are investigated at various concentrations. The obtained interfacial tensions are in good agreement with the experimental values reported in the literature. The results of this study can help elucidate the wetting and interfacial properties of aqueous imidazolium-based ILs.

Experimental and theoretical studies of five imidazolium-based ionic liquids as corrosion inhibitors for mild steel in H2S and HCl solutions

In this study, the mild steel corrosion inhibition performance and the corresponding mechanisms of five imidazolium-based ionic liquids (ILs) in hydrogen sulfide (H2S) and hydrochloric acid (HCl) solutions were investigated using electrochemical experiments, weight loss measurement, morphology analysis, and quantum chemical calculation. The results revealed that these ILs inhibited the corrosion of mild steel in H2S and HCl solutions and did not change the corresponding mechanism of the corrosion reaction. The corrosion inhibition ability of these ILs decreased when the temperature increased. 1-Allyl-3-methylimidazolium bromide ([Amim]Br) exhibited the strongest mild steel corrosion inhibition capacity in H2S and HCl solutions. The corrosion inhibition capacity of the ILs can be attributed to their adsorption on metal surfaces, which obeys the Langmuir adsorption isotherm. E HOMO exhibited a higher influence than E LUMO on the corrosion inhibition performance of the imidazolium-based ILs.

Enhancement of CO2/N2 selectivity and CO2 uptake by tuning concentration and chemical structure of imidazolium-based ILs immobilized in mesoporous silica

Imidazolium-based ionic liquids (ILs) with different cation alkyl chain ([i-C5mim] or [C4mim]) and inorganic anions ([Cl−], [Tf2N−], [PF6−] and [DCA−]) were synthesized and immobilized in commercial mesoporous silica. The synthesized supported ILs (SILs) were characterized using NMR, FTIR, TGA, BET, SEM and TEM. CO2 sorption capacity, reusability and CO2/N2 selectivity were assessed by the pressure-decay technique. The effects of IL concentration, cation and anion chemical structure in CO2 sorption capacity and CO2/N2 separation performance were evaluated. Tests evidenced that the presence of branching on the cation alkyl side chain increases CO2/N2 selectivity. The immobilization of the IL [i-C5TPIm][Cl] on mesoporous silica in different concentrations (50, 20, 10 and 5 %) revealed that lower IL concentration results in higher CO2 sorption capacity. Immobilization of ILs containing fluorinated anions at low concentrations in the mesoporous silica support may promote the improvement of the CO2/N2 selectivity without interfering on CO2 sorption capacity of the original support. CO2 sorption capacity value shown by sample SIL-5 % - [i-C5TPIm][Tf2N] (79.50 ± 0.70 mg CO2 g-1) was close to the value obtained for the pristine mesoporous silica (81.70 ± 2.20 mg CO2 g-1) and the selectivity (4.30 ± 0.70) was more than twice of the one obtained for the support alone (2.32 ± 0.4). Recycle tests demonstrated that the ILs immobilized in mesoporous silica samples are stable, providing a new option to be used in CO2 capture processes.

Fluorescence and Molecular Simulation Studies on the Interaction between Imidazolium-Based Ionic Liquids and Calf Thymus DNA

This work presents a molecular level investigation on the nature and mode of binding between imidazolium-based ionic liquids (ILs) ([Cnbim]Br where n = 2, 4, 6) with calf thymus DNA. This investigation offers valuable insight into the mechanisms of interactions that can affect the structural features of DNA and possibly cause the alteration or inhibition of DNA function. To expedite analysis, the study resorted to using molecular docking and COnductor like Screening MOdel for Real Solvents (COSMO-RS) in conjunction with fluorescence spectroscopic data for confirmation and validation of computational results. Both the fluorescence and docking studies consistently revealed a weak interaction between the two molecules, which corresponded to the binding energy of a stable docking conformation in the range of −5.19 to −7.75 kcal mol−1. As predicted, the rod-like structure of imidazolium-based ILs prefers to bind to the double-helix DNA through a minor groove. Interestingly, the occurrence of T-shape π-π stacking was observed between the amine group in adenine that faces the aromatic ring of imidazole. In addition, data of COSMO-RS for the interaction of individual nucleic acid bases to imidazolium-based ILs affirmed that ILs showed a propensity to bind to different bases, the highest being guanine followed by cytosine, thymine, uracil, and adenine.

Effect of alkyl chain length on the wetting behavior of imidazolium based ionic liquids: A molecular dynamics study

Molecular dynamics (MD) simulations are performed to investigate the wetting behavior of imidazolium-based ionic liquids (ILs), which mainly consist of an imidazolium ring with a flexible alkyl chain attachment. The length of the alkyl chain can be easily manipulated to modulate the wetting properties of the ILs. To understand the role of the alkyl chain, we investigate the wetting behavior of two room-temperature ionic liquids (RTILs), 1,3-dimethylimidazolium tetra-fluoroborate [DMIM][BF4] and 1-propyl-3-methylimidazolium tetra-fluoroborate [PrMIM][BF4], on a graphite surface. Furthermore, the effects of the droplet size and temperature on the contact angle of the IL droplets are investigated. The wetting behaviors of both IL droplets are characterized using a density profile and orientation order parameter profile along the axis normal to the surface. The length of the alkyl chain is found to be crucial for modulating the wetting properties of the ILs. With an increase in the length of the alkyl chain, the contact angle of the droplet decreases, which is also in line with experimental results [1,2]. The wetting of the IL droplets strongly depends on the temperature and the relative fluid-fluid and fluid-substrate interactions. With the increase in temperature, the contact angle of the IL droplet decreases, resulting in the formation of a single layer film at a high temperature. In addition, the behavior of the contact angle of the IL droplet is analyzed through the surface tension as well as the graphite-IL interfacial tension. Furthermore, considering the anisotropic properties of the imidazolium-based ILs, we calculate the contact angles for cylindrical filaments (2D) on the graphite surface and compare the obtained values with the contact angle obtained from the spherical droplet (3D). The contact angle of the cylindrical droplet is found to have a negligible system size effect as compared to the case with the spherical droplet.

110th Anniversary: The First Thermodynamic and Kinetic Analysis of Ammonia in Imidazolium-Based Ionic Liquids Using a Gravimetric Microbalance

The first vapor liquid equilibrium (VLE) measurements for the binary systems of ammonia (NH3) and three imidazolium-based ionic liquids (ILs) have been successfully measured using a gravimetric microbalance. ILs 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1im][BF4]), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][NTf2]) were measured at temperatures of 283.15, 298.15, 323.15, and 348.15 K and at pressures up to 0.7 MPa using the new Hiden XEMIS gravimetric microbalance. The VLE data were correlated using the Peng–Robinson equation of state and the Non-Random Two Liquid (NRTL) activity coefficient models. Both models are in excellent agreement with the experimental data. The Fickian diffusivities of NH3 in imidazolium-based ILs were obtained fitting experimental concentration to the one-dimensional (1D) mass diffusion equation, and found to be about 3 to 5 times lower than the diffusion of NH3 in water (H2O...

Effect of Imidazolium-Based Ionic Liquids on the Structure and Stability of Stem Bromelain: Concentration and Alkyl Chain Length Effect.

In the present work, changes in the structure and stability of stem bromelain (BM) are observed in the presence of a set of four imidazolium-based ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]), and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]), using various biophysical techniques. Fluorescence spectroscopy is used to observe the changes taking place in the microenvironment around the tryptophan (Trp) residues of BM and its thermal stability because of its interactions with the ILs at different concentrations. Near-UV circular dichroism results showed that the native structure of BM remained preserved only at lower concentrations of ILs. In agreement with these results, dynamic light scattering revealed the formation of large aggregates of BM at higher concentrations of ILs, indicating the unfolding of BM. In addition to this, the results also show that higher alkyl chain length imidazolium-based ILs have a more denaturing effect on the BM structure as compared to the lower alkyl chain length ILs because of the increased hydrophobic interaction between the ILs and the BM structure. Interestingly, it is noted that low concentrations (0.01-0.10 M) of short alkyl chain ILs only alter the structural arrangement of the protein without any significant effect on its stability. However, high concentrations of all five ILs are found to disrupt the structural stability of BM.

Imidazolium ionic liquids as effective antiseptics and disinfectants against drug resistant S. aureus: In silico and in vitro studies

This paper describes Quantitative Structure-Activity Relationships (QSAR) studies, molecular docking and in vitro antibacterial activity of several potent imidazolium-based ionic liquids (ILs) against S. aureus ATCC 25923 and its clinical isolate. Small set of 131 ILs was collected from the literature and uploaded in the OCHEM database. QSAR methodologies used Associative Neural Networks and Random Forests (WEKA-RF) methods. The predictive ability of the models was tested through cross-validation, giving cross-validated coefficients q2 = 0.82-0.87 for regression models and overall prediction accuracies of 80-82.1% for classification models. The proposed QSAR models are freely available online on OCHEM server at https://ochem.eu/article/107364 and can be used for estimation of antibacterial activity of new imidazolium-based ILs. A series of synthesized 1,3-dialkylimidazolium ILs with predicted activity were evaluated in vitro. The high activity of 7 ILs against S. aureus strain and its clinical isolate was measured and thereafter analyzed by the molecular docking to prokaryotic homologue of a eukaryotic tubulin FtsZ.

Evaluation and correlation of separation heptane/ethanol with ionic liquids. Ternary liquid-liquid phase equilibrium data

The objective of this work was to explore the feasibility of separation of heptane from ethanol using ammonium-based and imidazolium-based ionic liquids (ILs). With this aim, the liquid–liquid phase equilibrium (LLE) for four ternary systems of {IL (1) + ethanol (2) + heptane (3)} at temperature T = 313.15 K and pressure p = 101 kPa were determined. The synthesis of new ammonium-based ionic liquid (IL), N-benzyl-N-dimethyl-N-tetradecylammonium vannilliate, [NBz,1,1,14][Van] has been presented and used in LLE measurements. The results of selectivity of separation were compared to popular N-octyl-N-triethylammonium bis{(trifluoromethyl)sulfonyl}imide, [N8,2,2,2][NTf2], and two imidazolium-based ILs: 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM[TFA] and 1-hexyloxymethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [C6H13OCH2MIM][NTf2]. The [EMIM[TFA] IL showed excellent results in terms of selectivity and solute distribution ratio. On the basis of the results, the intermolecular interactions of the chosen ILs and solvents were discussed. The data presented here shows that [NBz,1,1,14][Van] reveals lower selectivity for the heptane/ethanol separation than the other used ILs. It allows expanding our knowledge about nature of the [NBz,1,1,14][Van], influence of polar functional groups and alkane chain in the cation on thermodynamical properties of [NBz,1,1,14][Van]. All experimental data were well correlated with the NRTL model.

Modeling interactions between a β-O-4 type lignin model compound and 1-allyl-3-methylimidazolium chloride ionic liquid.

Aiming at understanding the molecular mechanism of the lignin dissolution in imidazolium-based ionic liquids (ILs), this work presents a combined quantum chemistry (QC) calculation and molecular dynamics (MD) simulation study on the interaction of the lignin model compound, veratrylglycerol-β-guaiacyl ether (VG) with 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The monomer of VG is shown to feature a strong intramolecular hydrogen bond, and its dimer is indicated to present important π-π stacking and intermolecular hydrogen bonding interactions. The interactions of both the cation and anion of [Amim]Cl with VG are shown to be stronger than that between the two monomers, indicating that [Amim]Cl is capable of dissolving lignin. While Cl- anion forms a hydrogen-bonded complex with VG, the imidazolium cation interacts with VG via both the π-π stacking and intermolecular hydrogen bonding. The calculated interaction energies between VG and the IL or its components (the cation, anion, and ion pair) indicate the anion plays a more important role than the cation for the dissolution of lignin in the IL. Theoretical results provide help for understanding the molecular mechanism of lignin dissolution in imidazolium-based IL. The theoretical calculations on the interaction between the lignin model compound and [Amim]Cl ionic liquid indicate that the anion of [Amim]Cl plays a more important role for lignin dissolution although the cation also makes a substantial contribution.

New Insight into the Formation Mechanism of Imidazolium-Based Ionic Liquids from N-Alkyl Imidazoles and Halogenated Hydrocarbons: A Polar Microenvironment Induced and Autopromoted Process.

To illustrate the formation mechanism of imidazolium-based ionic liquids (ILs) from N-alkyl imidazoles and halogenated hydrocarbons, density functional theory calculations have been carried out on a representative system, the reaction of N-methyl imidazole with chloroethane to form 1-ethyl-3-methyl imidazolium chloride ([Emim]Cl) IL. The reaction is shown to proceed via an SN2 transition state with a free energy barrier of 34.4 kcal/mol in the gas phase and 27.6 kcal/mol in toluene solvent. The reaction can be remarkably promoted by the presence of ionic products and water molecules. The calculated barriers in toluene are 22.0, 21.7, and 19.9 kcal/mol in the presence of 1-3 ionic pairs of [Emim]Cl and 23.5, 21.3, and 19.4 kcal/mol in the presence of 1-3 water molecules, respectively. These ionic pairs and water molecules do not participate directly in the reaction but provide a polar environment that favors stabilizing the transition state with large charge separation. Hence, we propose that the synthesis of imidazolium-based ILs from N-alkyl imidazoles and halogenated hydrocarbons is an autopromoted process and a polar microenvironment induced reaction, and the existence of water molecules (a highly polar solvent) in the reaction may be mainly responsible for the initiation of reaction.