Interaction Of Ionic Liquids Research Articles

Caffeine-protic ionic liquid interactions in aqueous solutions evaluated by volumetric and spectroscopic studies

A comprehensive study on volumetric and spectroscopic properties of ternary solutions [water + protic ionic liquids (PILs) + caffeine (CAF)] was performed. Volumetric and compressibility properties were evaluated at different concentrations and temperatures, by measuring density and speed of sound of solutions. The newly synthesized PILs, ethanolammonium acetate; [EAAc] and ethanolammonium hexanoate; [EAHx] was used as co-solute. The density and speed of sound have been estimated at four different temperatures (298.15 K to 313.15 K) and at 0.1 MPa. Using these experimental data, apparent molar-volume, -isentropic compressibility, volumes of transfer were evaluated to understand the solute–solute, solute–solvent and solute–cosolute interactions occurring within the ternary solutions. At lower concentrations, negative transfer volumes indicate the presence of hydrophobic interactions among components of PILs (cations/anions) and CAF. The transfer volumes become positive as the concentration of PILs rises, implying that hydrophilic interactions were strengthened. In addition, UV–visible spectroscopic analysis was also performed to evaluate the nature of interactions. Hydrogen bonding interactions were also suggested based on the hyperchromic shift observed in UV absorption when aqueous CAF was titrated with PILs solutions. Physico-chemical analysis of the PILs-caffeine system are essential for comprehending the kinds of interactions that may occur in liquid combinations used for therapeutic drug delivery.

Conformation features and interaction of pyrrolidinium-based ionic liquids immobilized with silicon dioxide: Infrared spectroscopy

Ionic liquids (ILs) based on pyrrolidinium cation, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyrrTFSI) and 1-butyl-1-methylpirrolidinium dicyanamide (BMPyrrN(CN)2), were incorporated into the silica matrix (SiO2, particle size about 80 nm) by a simple mixing procedure. Semitransparent phase-stable ionogels with an IL content of more than 90 wt% have been obtained and studied by FTIR spectroscopy. The analysis of microscopic mechanisms of interaction, in particular, hydrogen bonding, was carried out using the procedure of fitting the characteristic bands of pure and confined ILs. The observed changes in the position and intensity of some characteristic frequencies were interpreted in terms of the interaction of SiO2 with IL. Under confined condition, the cis–trans equilibrium of both the TFSI− anion and BMPyrr+ cation changes in favor of the trans population due to the predominant interaction of cis conformers with silica walls. This data for confined BMPyrr-based ionic liquids were obtained in our study for the first time and will be useful for designing of a new nanostructured hybrid materials with promising properties.

The interaction of cholinium-based ionic liquids with different biological origin anions with albumins

The intermolecular interactions of cholinium-based ionic liquids (ILs) with biological origin anions (amino and dicarboxylic acids) with bovine serum albumin (BSA) and human serum albumin (HSA) have been studied by spectral and computational methods. The choline malonate ([Ch][Mal]), choline succinate ([Ch][Suc]) and choline valinate ([Ch][Val]) were synthesized. The changes to the state of the BSA and HSA with ILs at different concentration were observed using circular dichroism (CD) spectroscopy. At higher concentrations the ILs lead to a partial loss of ternary structure of albumins. The effect of ILs on the thermal stability of proteins was monitored by the temperature CD spectra scans. The increase of denaturation temperature of albumins with ionic liquids was observed. The interaction of ionic liquids with serum albumins was estimated by fluorescence spectroscopy technique, while the probable binding modes were identified using molecular docking. The leading cause of the increased thermal stability of albumins was found to be the formation of aggregates of proteins with ionic liquids. Cytotoxicity of ionic liquids on cancer and normal cell lines was established.

Unraveling the Molecular Interactions of Imidazolium-Based Surface-Active Ionic Liquid [C15mim][Br] with Biologically Active Amino Acids Glycine, l-Alanine, l-Valine

Unraveling the Molecular Interactions of Imidazolium-Based Surface-Active Ionic Liquid [C15mim][Br] with Biologically Active Amino Acids Glycine, l-Alanine, l-Valine

Understanding the catalytic behavior of ionic liquids in tetralin alkylation with α-olefins through experiment and COSMO-RS model

Using coal-based feedstocks to produce chemicals is of importance for the high value-added utilization of coal and the reduction of petroleum consumption. Alkyltetralins similar to naphthenic oil were successfully obtained through tetralin alkylation with various olefins. Various ionic liquids (ILs) were applied to catalyze alkylations, and Et3NHCl-AlCl3 IL exhibited high catalytic activity under mild reaction temperature (80 °C), the selectivity of multi-alkyltetralins higher than 70% could be achieved at >99% tetralin conversion. Such catalyst was shown to be robust in the presence of trace water and oxygenated chemicals. COSMO-RS model was applied to predict the mutual solubility and interaction of tetralin, olefins and alkyltetralins in ILs. The experimental and calculated results demonstrated that the favorable interactions of shorter-chain olefins and ILs benefited to produce multi-alkyltetralins, and the low mutual solubility of reactants and products in ILs was helpful to the rapid separation of products in the system.

Examining ionicity and conductivity in poly(methyl methacrylate) containing imidazolium-based ionic liquids

Ionic liquid (IL) interactions with amorphous polymers or polyelectrolytes attract interests due to their propensity to form ionogels with enhanced viscosity and reduced ionic conductivity when compared to their neat IL. A good understanding on the interactions between polymer and IL is needed to design better IL-based hybrid electrolytes. This study examines the mixtures of IL-polymer electrolytes with relatively low polymer concentration to improve their conductivity. Ion transport properties of three types of imidazolium-based ionic liquids are investigated with the addition of linear poly(methyl methacrylate) (PMMA) homopolymer. Dielectric properties of PMMA/IL mixtures indicated the enhancement of apparent ionicity of ILs, which is attributed to the preferential interactions between PMMA and bis(trifluoromethylsulfonyl)imide (TFSI-) anions. The frequency-dependent conductivity data analyzed by the Jonscher universal power law infer that ion–dipole coupling interactions between PMMA and IL help in the solvation and enhance the ionicity by disrupting the cage structure and facilitating the fast ion motions of IL.

Host-Guest Interactions of Zirconium-Based Metal-Organic Framework with Ionic Liquid.

A metal-organic framework (MOF) is a three-dimensional crystalline compound made from organic ligands and metals. The cross-linkage between organic ligands and metals creates a network of coordination polymers containing adjustable voids with a high total surface area. This special feature of MOF made it possible to form a host-guest interaction with small molecules, such as ionic liquid (IL), which can alter the phase behavior and improve the performance in battery applications. The molecular interactions of MOF and IL are, however, hard to understand due to the limited number of computational studies. In this study, the structural parameters of a zirconium-based metal-organic framework (UiO-66) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI] were investigated via a combined experimental and computational approach using the linker model approach. When IL was loaded, the bond length and bond angle of organic linkers were distorted due to the increased electron density surrounding the framework. The increase in molecular orbital energy after confining IL stabilized the structure of this hybrid system. The molecular interactions study revealed that the combination of UiO-66 and [EMIM][TFSI] could be a promising candidate as an electrolyte material in an energy storage system.

Molecular dynamics simulation studies of 1,3-dimethyl imidazolium nitrate ionic liquid with water.

The fundamental understanding of intermolecular interactions of ionic liquids (ILs) with water is essential in predicting IL-water thermodynamic properties. In this study, intermolecular or noncovalent interactions were studied for 1,3-dimethyl imidazolium [DMIM]+ cation and nitrate [NO3]- anion with water, employing quantum mechanics and molecular dynamics simulations. Molecular dynamics simulations were performed using a revised multipolar polarizable force field. The effect of water on ionic liquids was evaluated in terms of thermodynamic and dynamic properties. Thermodynamic properties included liquid densities ρ, excess molar volumes ΔVE, and liquid structures gr. Dynamic properties included self-diffusion coefficients D of mixture constituents as a function of water concentration. The density of ionic liquid-water mixtures monotonically decrease with increasing concentration of water. A negative excess volume was obtained for low and high water concentrations, demonstrating strong intermolecular interactions of water with ionic liquid components. Liquid structures of ionic liquid-water mixtures revealed a tendency for anions to interact with cations at shorter intermolecular distances when the water concentration is increased. Diffusion rates were found to increase for all mixture components with increase in the fraction of water. A significant change in the diffusion rate was found at ∼0.3 weight fraction of water. However, the water self-diffusion coefficient was dominant at all concentrations. The ratio of water/anion and anion/cation self-diffusion coefficients was found to decrease linearly with increasing concentration of water molecules.

Effect of water content on transport properties and interactions of amino-functionalized ionic liquids

Dual amino-functionalized ionic liquids (AFILs) have attracted great interest in recent years because of their application in catalysis and carbon capture industries. Density data for [aP4443][Gly] – water mixtures were supplementary measured with different water mass fractions at 296.15 K. Molecular dynamics (MD) simulation of [aP4443][Gly] – water and [aP4443][Ala] – water was carried out to research the effect of water content on the density, viscosity and the interactions of ILs - water. It was found that with the increase of water content, the density of ILs - water mixtures increased slightly and the viscosity decreased significantly. It was found that strong hydrogen bonding exits between anions and water, in which the interaction of [Gly]− - water was stronger than [Ala]− - water. Water molecules would form water clusters at lower water content. Furthermore, it could be found that with the increase of water content, all interactions were weakened.

INTERACTION OF IONIC LIQUIDS BASED ON BIS(TRIFLUOROMETHYLSULFONIL)IMIDE ANION WITH HALLOYSITE NANOTUBES ACCORDING TO FT-IR SPECTROSCOPY

In this work, FT-IR spectroscopy was used to study the interactions in ionogels of the composition х[X]+[TFSI]−/(100 - x)НNT, where [TFSI]– is the bis(trifluoromethylsulfonyl)imide anion, the cation [X]+ = [BMPip]+ (1-butyl-1-methylpiperidinium), [BMPyr]+ (1-butyl-1-methylpyrrolidinium), and [BMIm]+ (1-butyl-3-methylimidazolium), HNT are halloysite nanotubes, х = (55.2±0.5) wt.%. A comparison of the spectra of the starting compounds and the resulting ionogels showed that the characteristic frequency of the stretching vibrations of OH bonds of adsorbed water molecules, observed in the spectra of pure halloysite, practically vanishes in the spectra of ionogel sts. The stretching vibrations of the C-H bond atoms of the cation, ν(CH), and the stretching vibrations of the C-F bond atoms of the CF3 group of the anion, ν(CF3), in the spectra of limited ionic liquids are shifted to the high frequency region by 1-3 cm-1. The ratio of the intensities of the asymmetric bending vibrations of the S=O bond atoms of the SO2 group, I(δasopSO2)/I(δasipSO2), which correspond to two different conformational isomers of the anion, increases by (15-19)%. As a result, it was found that the H2O molecules of halloysite are replaced by molecules of the ionic liquid due to the electrostatic interaction of the cation with the negatively charged outer siloxane (–Si–O–Si–) surface of the nanotubes and hydrogen bonds (CH···OSi), and due to the electrostatic interaction of the anion with a positively charged internal aluminol (–Al–OH) surface and hydrogen bonds (CF···HO–Al, SO···HO–Al). The restriction of the ionic liquid in the internal cavity of the HNT causes a conformational rearrangement of the [TFSI]− anion. The results obtained are of fundamental importance, make a certain contribution to understanding the effects in ionogels based on ionic liquids and nanoporous natural minerals, and can be used to develop quasi-solid electrolytes in the production of various electrochemical devices. For citation: Ramenskaya L.M., Grishina E.P., Kudryakova N.O. Interaction of ionic liquids based on bis(trifluoromethylsulfonil)imide anion with halloysite nanotubes according to FT-IR spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 36-44. DOI: 10.6060/ivkkt.20236603.6752.

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.

Exploring nucleic acid stability in ionic liquids: Measurements and mechanisms.

The stability and integrity of nucleic acids, DNA and RNA, are vital in biotechnological applications. Conventionally, nucleic acids are stored under refrigeration for short and long-term applications as they are not stable at room temperature. Repeated freeze-thaw cycles are detrimental to the stability of nucleic acids and also remain a cost ineffective way of preservation. Ionic liquids (ILs), composed of organic cations and organic/inorganic anions, are shown to be promising solvent media for preservation of several biomolecules. Previously, we have shown that groove binding of IL cations through combined hydrophobic and polar interactions contribute significantly to the DNA stability.In this work, we attempt to understand the role of different class of ionic liquids in stabilizing DNA through experimental methods and explore their mechanism through molecular dynamic (MD) simulations. The ionic liquids of different class that are chosen involve ethyl ammonium nitrate [EAN] as protic, [BMIM]] [chloride] as a borderline between protic and aprotic, and [BMIM][acetate] as the aprotic IL. We employed UV-visible absorption spectroscopy and CD spectroscopy to investigate the interaction pattern between DNA and ILs and measure the structural integrity. The melting values (Tm) were recorded as a measure of stability. Further, we performed MD simulations and quantum calculations to understand the mechanism of interaction of ILs with DNA. Our findings show the significance of protic IL, [EAN] in stabilizing DNA to a greater extent with highest Tm value and a free energy of stabilization by −10.36 kcal/mol.

Biomass and Cellulose Dissolution—The Important Issue in Renewable Materials Treatment

Sustainable development strategies, as well as the shift toward a circular bioeconomy, has led to high interest in the development and implementation of technologies that efficiently utilize biomass as a raw material. Switching from fossil-based to bio-based resources requires the consideration of many new challenges and problems. One of the crucial issues is the solubility of lignocellulose or at least its ingredients. According to the trends and legislation, the selected chemicals and methods of dissolution/treatment should also be environmentally friendly. The pretreatment processes prepare biomass for further transformations (e.g., chemical, thermal including pyrolysis, or biological) to valuable products such as biofuels, bio-oils, Fine Chemicals, solvents, plastics, and many others. This review discusses the latest findings on the dissolution of biomass and its ingredients. The application of novel, green solvents such as ionic liquids or deep eutectic solvents is discussed in detail. The impact of the composition and structure of these solvents on the biomass/cellulose dissolution process, as well as the mechanism of cellulose–ionic liquid interaction, is presented. Some novel achievements in the usage of inorganic salts and specific metal complexes are also overviewed.

Structure and interactions of novel ether-functionalised morpholinium and piperidinium ionic liquids with lithium salts

Investigation of the thermodynamic and transport properties of four novel ether-functionalised piperidinium and morpholinium ionic liquids with LiFSI and LiTFSI salts, and Li-ion coordination in ionic liquids.

A screening of results on the decay length in concentrated electrolytes.

Screening of electrostatic interactions in room-temperature ionic liquids and concentrated electrolytes has recently attracted much attention as surface force balance experiments have suggested the emergence of unanticipated anomalously large screening lengths at high ion concentrations. Termed underscreening, this effect was ascribed to the bulk properties of concentrated ionic systems. However, underscreening under experimentally relevant conditions is not predicted by classical theories and challenges our understanding of electrostatic correlations. Despite the enormous effort in performing large-scale simulations and new theoretical investigations, the origin of the anomalously long-range screening length remains elusive. This contribution briefly summarises the experimental, analytical and simulation results on ionic screening and the scaling behaviour of screening lengths. We then present an atomistic simulation approach that accounts for the solvent and ion exchange with a reservoir. We find that classical density functional theory (DFT) for concentrated electrolytes under confinement reproduces ion adsorption at charged interfaces surprisingly well. With DFT, we study confined electrolytes using implicit and explicit solvent models and the dependence on the solvent's dielectric properties. Our results demonstrate how the absence vs. presence of solvent particles and their discrete nature affect the short and long-range screening in concentrated ionic systems.

Tailoring the supramolecular interaction of ionic liquids for high-sensitivity temperature monitoring under high pressure

By modulating the supramolecular interactions within ionic liquids to enhance temperature sensitivity, we have further engineered a high-pressure-resistant temperature sensor.

Dynamic Wetting of Ionic Liquid Drops on Hydrophobic Microstructures.

Ionic liquids (ILs)─salts in a liquid state─play a crucial role in various applications, such as green solvents for chemical synthesis and catalysis, lubricants, especially for micro- and nanoelectromechanical systems, and electrolytes in solar cells. These applications critically rely on unique or tunable bulk properties of ionic liquids, such as viscosity, density, and surface tension. Furthermore, their interactions with different solid surfaces of various roughness and structures may uphold other promising applications, such as combustion, cooling, and coating. However, only a few systematic studies of IL wetting and interactions with solid surfaces exist. Here, we experimentally and theoretically investigate the dynamic wetting and contact angles (CA) of water and three kinds of ionic liquid droplets on hydrophobic microstructures of surface roughness (r = 2.61) and packing fraction (ϕ = 0.47) formed by micropillars arranged in a periodic pattern. The results show that, except for water, higher-viscosity ionic liquids have greater advancing and receding contact angles with increasing contact line velocity. Water drops initially form a gas-trapping, CB wetting state, whereas all three ionic liquid drops are in a Wenzel wetting state, where liquids penetrate and completely wet the microstructures. We find that an existing model comparing the global surface energies between a CB and a Wenzel state agrees well with the observed wetting states. In addition, a molecular dynamic model well predicts the experimental data and is used to explain the observed dynamic wetting for the ILs and superhydrophobic substrate. Our results further show that energy dissipation occurs more significantly in the three-phase contact line region than in the liquid bulk.

1,8‐diazabicyclo [5.4.0] undecano‐7‐ene functionalized ionic liquids for extractive desulfurization of fuels

AbstractBACKGROUNDWith strict regulations on environmental protection, the removal of sulfur compounds from fuels has become increasingly urgent by extraction desulfurization technology.RESULTSA series of ionic liquid (IL) extractants for the removal of sulfides [benzothiophene (BT), thiophene (TH) and dibenzothiophene (DBT) in model oil] was developed. The ILs with functionalized 1,8‐diazabicyclo [5.4.0] undecano‐7‐ene (DBU) cations and large volume difluoromethane sulfonimide (NTf2) anion as raw materials were synthesized. The performance of the ILs was characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis and nuclear magnetic hydrogen spectroscopy (1H‐NMR) and other methods. Maximum removal efficiencies of 65.08% TH, 83.02% BT and 89.72% DBT were achieved in the presence of [CoDBU][NTf2] with functionalized carboxylation groups. In addition extractive desulfurization (EDS) was studied by tailoring the acid–base functional groups and viscosity of ILs. FTIR and the analysis of interaction energies were adopted to explore the interaction of ILs and sulfides. This indicated that the cooperative effects of hydrogen bonding, electrostatic interaction and π‐π interaction between sulfides and ILs were closely related to the high removal efficiencies of sulfides.CONCLUSIONSThe experimental results show that [CoDBU][NTf2] with functional carboxyl group is a clean and efficient extractant suitable for removing thiophene sulfides from model fuel oil. This work provides a reference process for the desulfurization of fuel oil in industry. © 2022 Society of Chemical Industry (SCI).

Influence of alkali metals on water dynamics inside imidazolium-based ionic liquid nano-domains.

The global need to expand the design of energy-storage devices led to the investigation of alkali metal - Ionic Liquid (IL) mixtures as a possible class of electrolytes. In this study, 1D and 2D Nuclear Magnetic Resonance (NMR) and Electrochemical Impedance Spectroscopy (EIS) as well as Molecular Dynamics (MD) simulations were used to study the intermolecular interactions in imidazolium-based IL - water - alkali halide ternary mixtures. The 1H and 23Na 1D and 1H DOSY NMR spectra revealed that the presence of small quantities of NaCl does not influence the aggregation of water molecules in the IL nano-domains. The order of adding ionic compounds to water, as well as the certain water and NaCl molecular ratios, lead to the formation of isolated water clusters. Two ternary solutions representing different orders of compounds mixing (H2O+ IL + NaCl or H2O+ NaCl + IL) showed a strong dependence of the initial solvation shell of Na+ and the self-clustering of water. Furthermore, the behaviour of water was found to be independent from the conditions applied during the solution preparation, such as temperature and/or duration of stirring and aging. These findings could be confirmed by large differences in the amount of ionic species, observed in the ternary solutions and depending on the order of mixing/solute preparation.

Computational investigation of conformational fluctuations of Aβ42 monomers in aqueous ionic liquid mixtures

Aggregation of intrinsically disordered proteins (IDPs) is often triggered by protein–protein interaction, leading to several neurodegenerative diseases.In this study, we aim to understand the role of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] ionic liquid (IL) on altering secondary structure of the peptide and study the interactions responsible for their conformational modification. Here we report structural features of an ensemble of amyloid beta (Aβ42) peptide monomers employing all-atom molecular dynamics simulations in aqueous solution of IL at room temperature. Our calculations reveal, Aβ42 peptide exhibit rapidly inter-converting conformations adopting extended chain as well as collapsed coil-like structures with a propensity to form few transient α-helices and β-sheets at intermediate times. We have correlated this higher flexibility of the peptide with formation of less stable salt-bridge in presence of IL in aqueous solution. It is found that water molecules around the polar regions are more structured imparting structural rigidity to the peptide backbone than around the hydrophobic domains. Thus identifying the effect of electrostatic interaction of IL on expulsion of water molecules from the polar domains on the peptide surface can shed light on preventing the aggregation process. We have also determined the most energetically stable peptide conformations from various accessible intermediate states using metadynamics simulations that are characterized by the rugged free energy surface having multiple energy basins.