Chemical Properties Of Ionic Liquids Research Articles

The State of Water in "Ionic Liquid [bmim]Cl/AlCl3/H2O" Systems.

The unique physical and chemical properties of ionic liquids (ILs) determine their numerous applications in "green" chemistry and material science. Recently, systems based on ILs have been considered to be promising for use in a new generation of electrochemical devices. The results of a nuclear magnetic resonance (NMR) study of the microstructure of 1-butyl-3-methylimidazolium chloride (IL)/water mixtures in the presence of Al3+ cations are presented. For the first time, the splitting of spectral lines of water in such systems has been recorded. Comparing the 1H and 27Al NMR data, we have detected the existence of different solvate complexes of Al3+ with Cl- and estimated the characteristic times of exchange processes. For the system under study, a model of the Al3+ cation environment and its evolution with temperature and water content has been described. Quantum-chemical calculations have been performed to substantiate the model.

Spectroscopic and Chemical Properties of Ionic Liquids: Computational Study.

A brief account is given of highlights of our computational efforts - often in collaboration with experimental groups - to understand spectroscopic and chemical properties of ionic liquids (ILs). Molecular dynamics, including their inhomogeneous character, responsible for key spectral features observed in dielectric absorption, infra-red (IR) and fluorescence correlation spectroscopy (FCS) measurements are elucidated. Mechanisms of chemical processes involving imidazolium-based ILs are illustrated for CO2 capture and related reactions, transesterification of cellulose, and Au nanocluster-catalyzed Suzuki cross-coupling reaction with attention paid to differing roles of IL ions. A comparison with experiments is also made.

Molecular mechanism and extraction performance evaluation of ionic liquids for extraction process of n-heptane/n-propanol

• The intermolecular hydrogen bond interaction was analyzed based on COSMO-SAC. • The separation mechanism of azeotrope with ILs extractant was studied. • The weak interaction between ILs and n-propanol was analyzed by QC and MD. • The separation process of azeotrope was designed based on the optimal extractant. • The optimal operation parameters were determined by optimization. The use of the n-propanol/n-heptane mixture is known to reduce the content of lead in gasoline. Based on the unique physical and chemical properties of ionic liquids (ILs), such as extremely low volatility, research on the IL-based extraction of azeotropic systems has attracted increasing attention. In this study, experimental results were explained using theoretical analyses. σ-profiles were constructed on the quantum chemistry calculation, and the figure showed that the formation of hydrogen bonds between the ILs and n-propanol was probed. The weak interaction between ILs and n-propanol was qualitatively analyzed using reduced-density-gradient function, electrostatic potential, and bond length analyses. The mechanism by which ILs promoted the separation of the n-propanol/n-heptane azeotropic system was analyzed at the molecular level, thereby providing guidance for the selection of extractants. The liquid–liquid extraction process of n-propanol and n-heptane using [DMIM][MP] as an extractant was established using the Aspen Plus software. The effects of the application of ILs in liquid–liquid extraction was simulated, and the results provided basic data and theoretical references for the practical application of ILs in azeotropic liquid–liquid extraction.

Comparison of Pure and Hybrid Nanoparticles using Ionic Liquid as a Capping agent

Ionic liquids are exceptional chemical compounds that are used in many areas of modern science. Due to their highly adjustable nature and incomparable properties, ionic liquids have become key players in the areas of synthesis, catalysis, extraction, electrochemistry, analysis, biotechnology, etc. In addition to the physical and chemical properties of ionic liquids, their high biological activity has attracted considerable attention from biochemists, ecologists and medical professionals. Due to the properties mentioned above, an imidazolium ionic liquid solvent was used for the synthesis of nanostructure nanoparticles. In the present work, cubic form of pure Fe2O3, spherical nature of pure Ag (0) and hexagonal shaped hybrid Ag- Fe2O3 were successfully synthesized by a simple co-precipitation, reduction and co-precipitation processes. The synthesized nanoparticles were characterized in detail by spectral studies such as IR, XRD, SEM, EDX and TEM analysis. The size and shape of the particles were performed by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) techniques and Transmission Electron Microscope (TEM) techniques. Quality quantity and purity of the products was checked by Energy Dispersive X-Ray Analysis (EDX).

Synthesis, characterization and supercapacitor application of ionic liquid incorporated nanocomposites based on SPSU/Silicon dioxide

In this study, we report about novel polymer electrolytes containing sulfonated polysulfone (SPSU) as the polymer matrix, silicon dioxide (SiO2) as nano additive and ionic liquid (1-Ethyl-3-methyl-imidazolium tetrafluoroborate) IL) as a softening agent. In addition, the physical and chemical properties of ionic liquid containing nanocomposite gel polymer electrolytes were studied and subsequently the optimized electrolyte was used to assemble the supercapacitor device. Nanocomposite gel polymer electrolytes demonstrated higher thermal stability and lower glass transition temperatures (Tg) required for supercapacitor application. The ion conductivity of the nanocomposite polymer electrolytes was investigated using a dielectric-impedance analyzer at various temperatures. The highest conductivities were obtained for the samples SPSU/0.1IL and SPSU/%3n SiO2/0.2IL with values 3.1 × 10−4 and 3.2 × 10−3 S cm−1 at 100 °C, respectively. In addition, symmetrical cell formation based on Al/C/SPSU/%3nSiO2/0.2IL/C/Al showed a maximum specific capacitance of 134.1 F g−1 at 1 A g−1. The same cell also yielded a maximum energy density in supercapacitor as 18.6 Wh kg−1 at a power density of 1089 W kg−1.

Design Principles of Ionic Liquids for Transdermal Drug Delivery.

Ionic liquids (ILs) and deep eutectic solvents have shown great promise in drug delivery applications. Choline-based ILs, in particular choline and geranic acid (CAGE), have been used to enhance the transdermal delivery of several small and large molecules. However, detailed studies outlining the design principles of ILs for transdermal drug delivery are still lacking. Using two model drugs of differing hydrophilicities, acarbose and ruxolitinib and 16 ILs, the dependence of skin penetration on the chemical properties of ILs is examined. First, the impact of ion stoichiometry on skin penetration of drugs is assessed using CAGE, which evidences that a molar ratio of 1:2 of choline to geranic acid yields the highest delivery. Subsequently, variants of CAGE are prepared using anions with structural similarity to geranic acid and cations with structural similarity to choline at a ratio of 1:2. Mechanistic studies reveal that the potency of ILs in enhancing transdermal drug delivery correlates inversely with the inter-ionic interactions as determined by 2D NMR spectroscopy. Using this understanding, a new IL is designed, and it provides the highest delivery of ruxolitinib of all ILs tested here. Overall, these studies provide a generalized framework for optimizing ILs for enhancing skin permeability.

High-Yield Urea Electrochemistry Synthesis Derived from Direct CO2 Activation in Ionic Liquid

In this work, we present a facile electrochemical approach to synthesize urea from amines and CO2 directly using ionic liquid (IL) as the catalyst. This procedure works could give urea without the addition of any additives or tedious work-up. The results indicated that cyclohexylamine, cyclopentylamine, pentylamine and octylamine was converted to high yield of corresponding urea through a very low-potential (~1.0 V) CO2 activation in ionic liquid. The yield and selectivity of urea production exhibited a strong dependence on the structure of amine and ionic liquid. This process was considered as an E-C process that initiated from our recent discovered CO2 activation. This new chemistry described here may be particularly used for understanding the chemical properties of ionic liquid and particularly provide a promising lead for the development of practical catalysis for the low-cost urea synthesis.

Structural Anomalies in Ionic Liquids near the Glass Transition Revealed by Pulse EPR.

Unusual physical and chemical properties of ionic liquids (ILs) open up prospects for various applications. We report the first observation of density/rigidity heterogeneities in a series of ILs near the glass transition temperature ( Tg) by means of pulse electron paramagnetic resonance (EPR). Unprecedented suppression of molecular mobility is evidenced near the glass transition, which is assigned to unusual structural rearrangements of ILs on the nanometer scale. Indeed, pulse and continuous wave EPR clearly indicate the occurrence of heterogeneities near Tg, which exist in a rather broad temperature range of ∼50 K. The two types of local environments are evidenced, being drastically different by their stiffness. The more rigid one suppresses molecular mobility, whereas the softer one instead promotes diffusive molecular rotation. Such properties of ILs near Tg are of general importance; moreover, the observed density/rigidity heterogeneities controlled by temperature might be considered as a new type of tunable reaction nanoenvironment.

Broadband Terahertz Spectroscopy of Imidazolium-Based Ionic Liquids.

Ionic liquids are liquid salts at ambient temperature composed of organic cations and organic/inorganic anions. Outstanding physical and chemical properties of ionic liquids lead to increasing application in scientific and industrial field. Ionic liquids have been already investigated by different spectroscopic techniques, including terahertz (THz) time-domain spectroscopy. The usual THz frequency range extends up to 2-3 THz, a relatively narrow band, which can only show the intermolecular vibrational modes. Here, we report about broadband THz spectroscopy of ionic liquids up to 13 THz. Bandwidth of intermolecular absorption band presents an unexpected behavior and strong sharp intramolecular absorptions are shown. In addition, we found violation of the approximation of harmonic oscillator used to predict the peak shift of intermolecular absorption band.

The influence of ionothermal synthesis using BmimBF4 as a solvent on nanophosphor BaFBr:Eu2+ photoluminescence.

Ionothermal synthesis is a strongly growing research area due to the outstanding physical and chemical properties of ionic liquids (ILs) in the design of new materials, however, the interaction of these IL molecules with optical materials and their effect on the luminescence properties of the materials are poorly known. In this work, it is shown that the imidazolium based BmimBF4 ionic liquid, used as a solvent during the synthesis, tethers at the surface of the nanoparticles and influences the photoluminescence of the nanophosphor BaFBr:Eu2+ materials. In time resolved spectra, two different emissions are observed for the material synthesized by the ionothermal approach, one corresponding to Eu(ii) 5d-4f transitions in the BaFBr host with a decay time of 843 ns and the other with a much faster decay time compared to the ionic liquid BmimBF4.

A review on electrochemical properties of choline chloride based eutectic solvent in mineral processing

Our review highlights the most recent developments in ionic liquid (IL) chemistry where the “well-known” description of IL properties sometimes proves to be inaccurate. However, in the authors’ opinion, all these new research developments concerning ionic liquid properties serve to update knowledge on the typical physical and chemical properties of ILs, which is significant to both theoretical research and industrial applications. Therefore, rather than attempting to give a comprehensive overview of ionic liquid chemistry, the paper presents an opportunity to understand deep eutectic solvents (DES) through a more complete and accurate view. Keywords: Eutectic; Solvents; Electrochemistry; Ionic Liquids; purification; Ethylene glycol

Confinement Effects on an Electron Transfer Reaction in Nanoporous Carbon Electrodes

Nanoconfinement generally leads to a drastic effect on the physical and chemical properties of ionic liquids. Here we investigate how the electrochemical reactivity in such media may be impacted inside of nanoporous carbon electrodes. To this end, we study a simple electron transfer reaction using molecular dynamics simulations. The electrodes are held at constant electric potential by allowing the atomic charges on the carbon atoms to fluctuate. We show that the Fe3+/Fe2+ couple dissolved in an ionic liquid exhibits a deviation with respect to Marcus theory. This behavior is rationalized by the stabilization of a solvation state of the Fe3+ cation in the disordered nanoporous electrode that is not observed in the bulk. The simulation results are fitted with a recently proposed two solvation state model, which allows us to estimate the effect of such a deviation on the kinetics of electron transfer inside of nanoporous electrodes.

Hydrogen bonding mediated ion pairs of some aprotic ionic liquids and their structural transition in aqueous solution

Ion pair speciation of ionic liquids (ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them. Considering the fact that far-IR (FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding, in this work, this spectroscopic technique has been combined with molecular dynamic (MD) simulation and nuclear magnetic resonance hydrogen spectroscopy (1H NMR) to investigate ion pairs of aprotic ILs [Bmim][NO3], [BuPy][NO3], [Pyr14][NO3], [PP14][NO3] and [Bu-choline][NO3] in aqueous IL mixtures. The FIR spectra have been assigned with the aid of density functional theory (DFT) calculations, and the results are used to understand the effect of cationic nature on the structure of ion pairs. It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion, were still maintained in aqueous solutions up to high water mole fraction (say 0.80 for [BuPy][NO3]). When water content was increased to a critical mole fraction of water (say 0.83 for [BuPy][NO3]), the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water. With the further dilution of the aqueous ILs solution, the solvent-separated ion pairs was finally turned into free cations and free anions (fully hydrated cations or anions). The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions (fully hydrated ion) were dependent on the cationic structures. These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous solution. MD simulation and 1H NMR results support the conclusion drawn from FIR spectra investigations.

A computational intelligence scheme for estimating electrical conductivity of ternary mixtures containing ionic liquids

Due to unique physical and chemical properties of ionic liquids (ILs), they received lots of attention in many industrial fields and are widely under research. Ionic liquids, also are emerging as important components for applications in electrochemical devices. To develop their applications and achieving desire properties, they are usually mixed with organic solvents. Applying ionic liquids in many applications needs the accurate and reliable data of electrical conductivity of ILs and their mixtures. To this end, a total of 224 experimental data were collected from literature and divided randomly into two datasets: 179 data was selected as training set and the remained 45 data was used as a testing set. Afterwards, a reliable modeling technique is developed for modeling the electrical conductivity of the ILs ternary mixtures. This approach is called least square support vector machine (LSSVM). The model parameters were optimized using the method of couple simulated annealing (CSA). The input model parameters were, temperature of the system, melting point, molecular weight and mole percent of each component. A comprehensive error investigation was carried out, yielding the well accordance between the predictions of the model and experimental data. The presented model can predict the dependency of electrical conductivity variations with input variables. Moreover, the sensitivity analyses demonstrated that, among the selected input parameters, the average melting point of mixture has the largest effect on the electrical conductivity. Furthermore, suspected data were detected using the Leverage approach, residual, Williams plot and statistical hat matrix. Except seven data points, the all data appear to be reliable.

Determination of thermodynamics and design parameters for ionic liquid-induced cloud point extraction of Coralene red dye

In the last decade, increasing interest on the use of aqueous micellar solution has been found in the field of separation science. The unique physical and chemical properties of ionic liquids make them most suitable candidates as an additive with nonionic surfactants in cloud point extraction. A surfactant-mediated cloud point extraction process has been adopted for the removal of Coralene red dye using tetraethyl ammonium tetrafluoroborate ionic liquid as an additive with nonionic surfactant Triton X-100. The detailed study on effect of various operating parameters such as temperature, time, concentration of surfactant, dye and IL on extraction of dye has been carried out to find out optimum conditions. The extraction of dye was found to be increased with temperature, time, surfactant concentration and IL concentration. A developed Langmuir isotherm was used to compute the feed surfactant concentration required for the removal of Coralene red dye up to an extraction efficiency of 90 %. The effect of temperature and concentration of surfactant and dye on various thermodynamic parameters was examined, and it was found that the values of ΔG 0 increased with temperature and decreased with surfactant and dye concentration. The values of ΔH 0 and ΔS 0 increased with surfactant concentration and decreased with dye concentration. The developed approach for IL-assisted cloud point extraction has proved to be an efficient and green route for extraction of Coralene red from water sample.

Shaping micro- and macroscopic properties of ionic liquid–solute systems: Multi-functional task-specific agents

It is well known that the physical and chemical properties of ionic liquids are dependent on their structure. Understanding the types and strengths of interactions is necessary for a knowledge-based design of ionic liquid structures. In the first section, we introduce some of our recent physico-chemical and spectroscopic investigations on binary ionic liquid+solute mixtures (with water, an organic solute or a second ionic liquid), showing that hydrogen bonding plays a vital role for the arrangement of the ions in mixtures, and preferential interactions can lead to subtle changes resulting in deviation from ideal mixing behavior. The second section shows examples of how specific interactions with solutes affect reactions and other processes, regarding e.g. the rate of reaction, yields, extraction efficiencies, dissolution capacities of biofeeds, and selectivity in crystal framework formation. The third section is dedicated to some examples regarding the development of ionic liquids as materials.

Applications of ionic liquids in chromatographic analysis and determination of ionic liquids by chromatography

As a kind of excellent solvent, ionic liquids have received more attentions. Because of the special physical and chemical properties of ionic liquids, ionic liquids have been more widely used in chromatography. This paper summarizes the applications of ionic liquids in gas chromatography, liquid chromatography and capillary electrophoresis, which include ionic liquids used as stationary phase in gas chromatography, stationary phase and mobile phase additive in liquid chromatography and electrolyte additives in capillary electrophoresis. The determination of ionic liquids by chromatography has also been introduced.

Thermodynamic Performance of Absorption Heat Transformer Using a New Working Pair: Water+Ionic Liquid 1,3-dimethylimidazolium Dimethylphosphate

In present research ionic liquid, 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and water were taken as the new working pair for absorption heat transformer (AHT). The thermodynamic cycle performance for this working pair was simulated based on its thermodynamic data, mass and energy balance for each component in a AHT. The effects of absorption and condensing temperature on the coefficient of performance (COP), exergy efficiency (ECOP), concentration deference between dense and dilution solutions and flow rate ratio were analyzed. The cycle performance comparison for AHT using two working pairs, H2O + [MMIM][DMP] and H2O + LiBr was carried out. The results indicate that the COP and ECOP of AHT for H2O+ [MMIM][DMP] are all lower than those for H2O + LiBr, but they can still reach 0.4 and 0.5 respectively when condensing and generation temperatures are 35 and 90 °C respectively. The excellent physical and chemical properties of ionic liquid mentioned above together with suitable cycle performance make this new working pair to have the potential application in absorption heat pump or absorption heat transformer.

A novel aromatically functional polymeric ionic liquid as sorbent material for solid-phase microextraction

Physical and chemical properties of ionic liquids (ILs) are significantly affected by types of their cations and anions. In this paper, a novel aromatically functional 1-vinyl-3-octylimidazolium 2-naphthalene-sulfonate salt was synthesized through metathesis reaction between 1-vinyl-3-octylimidazolium bromide and sodium 2-naphthalene-sulfonate, and polymerized onto the stainless steel wire in situ via surface radical chain-transfer reaction. Octanol/water distribution coefficient of the ionic liquid was studied and compared with that of 1-vinyl-3-octylimidazolium hexafluorophosphate. Partition coefficients of polycyclic aromatic hydrocarbons (PAHs) on these two polymeric ionic liquids-coated fibers indicated the enhanced hydrophobicity and aromaticity of the target IL. Analytical parameters exhibited high extraction efficiency of the novel fiber. Calibration ranges for several PAHs were from 0.02 to 200μgL−1. Limits of detection (LODs) were ranged from 0.005 to 0.01μgL−1. Application reliability of the proposed fiber was also investigated with some phthalate ester plasticizers. LODs were ranged from 0.02 to 0.05μgL−1. Hair spray and nail polish were used as real samples, and di-n-butyl phthalate and di-(2-ethyl-hexyl) phthalate were quantified with the established method.

Towards large-scale, fully ab initio calculations of ionic liquids

Ionic liquids have attracted a substantial amount of interest as replacement of traditional electrolytes in high efficiency electrochemical devices for generation and storage of energy due to their superior physical and chemical properties, especially low volatility and high electrochemical stability. For enhanced performance of the electrochemical devices ionic liquids are required to be highly conductive and low viscous. Long-range Coulomb and short-range dispersion interactions between ions affect physical and chemical properties of ionic liquids in a very complex way, thus preventing direct correlations to the chemical structure. Considering a vast combination of available cations and anions that can be used to synthesize ionic liquids, development of predictive theoretical approaches that allow for accurate tailoring of their physical properties has become crucial to further enhance the performance of electrochemical devices such as lithium batteries, fuel and solar cells. This perspective article gives a thorough overview of current theoretical approaches applied for studying thermodynamic (melting point and enthalpy of vapourisation) and transport (conductivity and viscosity) properties of ionic liquids, emphasizing their reliability and limitations. Strategies for improving predictive power and versatility of existing theoretical approaches are also outlined.