Applications of functionalized ionic liquids

Recent developments of the synthesis and applications of functionalized ionic liquids (including dual-functionalized ionic liquids) have been highlighted in this review. Ionic liquids are at-tracting attention as alternative solvents in green chemistry, but as more functionalized ILs are pre-pared, a greater number of applications in increasingly diverse fields are found.     

All-atom and united-atom simulations of guanidinium-based ionic liquids

Ionic liquids (ILs) have been widely used in separation, catalysis, electrochemistry, etc., and one of the most outstanding characteristics is that ILs can be tailored and tuned for specific tasks. In order to design and make better use of ionic liquids, the structures and properties relationship is indispensable. Both molecular dynamics and Monte Carlo simulations have been proved useful to understand the behavior of molecules at the microscale and the properties of the system. However, the quality of such simulations depends on force field parameters describing the interactions between atoms. All-atom (AA) or the united-atom (UA) force fields will be chosen because of the demand for more exact results or the lower computational cost, respectively. In order to make a systematic comparison of the two force fields, molecular simulations for four kinds of acyclic guanidinium-based ionic liquids (cations: (R2N)2C=N+<, anion: nitric or perchloric acid) were performed based on the AA and the UA force fields in this work. AA force field parameters were derived from our previous work (Fluid Phase Equilib., 2008, 272: 1-7), and the UA parameters were proposed in this work. Molecular dynamics simulation results for the AA and UA force fields were compared. Simulation densities are very similar to each other. Center of mass radial distribution functions (RDFs), site to site RDFs and spatial distribution functions (SDFs) were also investigated to depict the microscopic structures of the ILs.     

Separation of ionic liquids from dilute aqueous solutions using the method based on CO2 hydrates

Ionic liquids (ILs) have been regarded as the potential novel solvents for improved analytical-and process-scale separation methods. The development of methods for the recovery of ILs from aqueous solutions to escape contamination and recycle samples will ultimately govern the viability of ILs in the future industrial applications. Therefore, in this paper a new method for separation of ILs from their dilute aqueous solutions and simultaneously purification of water was proposed on the basis of the CO2 hydr...     

Direct polycondensation in ionic liquids

Ionic liquids (ILs) are subject to an enormous research effort due to their unique properties, such as non-volatility, high solution and reactivity ability, etc. For the first time ILs have been used as a solvent for preparing polymers via direct polycondensation. The influence of IL's nature and reaction parameters upon the polymer formulation has been investigated. It is shown that direct polycondensation is successfully proceeded in ILs and triphenyl phosphite (condensing agent) without any additional extra components, such as LiCl and pyridine, using in similar reactions in ordinary molecular solvents. Various polyamides (η_inh=0.11-1.10 dl/g), polyamide imides (η_inh=0.48-1.41 dl/g), -hydrazides (η_inh=0.56-0.60 dl/g) and polyhydrazides (η_inh=0.71-1.32 dl/g) have been obtained in quantitative yield and high molecular weight.     

Cation and anion substitution effects on the ultrafast dynamics of interionic interaction in imidazolium based ionic liquids

Room-temperature Ionic Liquids(ILs) have numerous unique properties that differ from those of conventional molecular solvents.Although the unique properties of ILs have been suggested to origin from their microscopic interionic interaction,detailed dynamics of interionic interaction of ILs has not been fully understood.Here,with the Femtosecond Optical Heterodyne-Detected Raman Induced Kerr Effect Spectroscopy(fs-OHD-RIKES),we measured the ultrafast dynamics of the interionic interaction of three typical im...     

New task-specific ionic liquids as bifunctional organocatalysts; Synthesis,characterization, and computational insights

A new class of functionalized imidazolium-based Task-Specific Ionic Liquids (TSILs) is designed as low-cost bifunctional organocatalyst. New alkoxymethylimidazolium ILs are efficiently synthesized under solvent free conditions and extensively characterized by physical and spectral studies. The newly synthesized ILs demonstrate excellent catalytic potential in condensation reactions of high importance, such as the Biginelli reaction for the synthesis of medicinally important dihydropyrimidiones. The effect of the alkoxy group and counter-ions in the imidazolium salts were evaluated in detail. Moreover, computational studies were employed to explore the structural dynamics and physicochemical properties of the prepared ionic liquids. 3-(iso-butoxymethyl)-1-methyl-1H-imidazol-3-ium tetrafluoroborate (ⁱBOMMIMBF₄ 7) exhibited the highest catalytic ability due to the combined influence of the alkoxy group structure, counterion nature, high electrophilicity index, and availability of the reactive C2-H. Some notable advantages of the new TSILs include efficient catalyst preparation, simple work-up procedure, recyclability, short reaction times, and excellent yields.     

Surface-bonded ionic liquid stationary phases in high-performance liquid chromatography—A review

Ionic liquids (ILs) are a class of ionic, nonmolecular solvents which remain in liquid state at temperatures below 100 °C. ILs possess a variety of properties including low to negligible vapor pressure, high thermal stability, miscibility with water or a variety of organic solvents, and variable viscosity. IL-modified silica as novel high-performance liquid chromatography (HPLC) stationary phases have attracted considerable attention for their differential behavior and low free-silanol activity. Indeed, around 21 surface-confined ionic liquids (SCIL) stationary phases have been developed in the last six years. Their chromatographic behavior has been studied, and, despite the presence of a positive charge on the stationary phase, they showed considerable promise for the separation of neutral solutes (not only basic analytes), when operated in reversed phase mode. This aspect points to the potential for truly multimodal stationary phases. This review attempts to summarize the state-of-the-art about SCIL phases including their preparation, chromatographic behavior, and analytical performance.     

Are deep eutectic solvents a real alternative to ionic liquids in metal-catalysed reactions?

This microreview tries to answer the question: Are Deep Eutectic Solvents a real alternative to Ionic Liquids in metal-catalysed reactions? We have gathered the outstanding results of the use of DES in metal-catalysed processes and we have compared them to the ones with ILs. The huge possibilities of combinations of the components of the DES provide a vast number of different solvents with tunable properties. These DES have been successfully applied to different reactions such as, couplings or hydrogenations, among others. But additional work is still be necessary to explore the use of DES in other reactions and to go in depth in the study of the influence of the nature of the DES. Finally, we also present the rise in a new family of solvents, bio-based ionic liquids, complementary to the use of DES in order to fully substitute traditional ILs.     

Task-specific microextractions using ionic liquids

Ionic liquids (ILs) have been the focus of many scientific investigations including the field of analytical microextractions. ILs have many advantages over traditional organic solvents making them excellent candidates as extraction media for a variety of microextraction techniques. Many physical properties of ILs can be varied, and the structural design and make-up can be tuned to impart desired functionality for enhancement of analyte extraction selectivity, efficiency, and sensitivity. This paper provides a brief overview of ionic liquids and highlights trends in three important sample-preparation techniques, namely, single drop microextraction, solid-phase microextraction, and dispersive liquid–liquid microextraction in terms of performing task-specific extractions using these highly versatile solvents.     

Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

Micellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C₆mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C₈mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C₆mim][Br] and [C₈mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C₄mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.     

Task-specific ionic liquids for carbon dioxide absorption and conversion into value-added products

Ionic liquids (ILs), by virtue of their special properties such as functional designability and high thermal stability, have been widely used as absorbent to CO₂ and catalyst for CO₂ conversion. This review summarizes the recent developments from 2019 to 2021 on task-specific ionic liquids (TSILs) with modulable properties by introducing specific functional groups to anions or/and cations for CO₂ absorption and conversion. The increase of basicity in TSILs by introducing amino/or amine groups or collaboration with multiple active sites of carboxyl, imidazolyl, pyridyl, and hydroxyl groups achieve high CO₂ affinity and absorption capacity. To solve the defects of high viscosity, ether groups are introduced to TSILs for CO₂ absorption. Besides, recent studies on CO₂ thermal catalytic conversion focused on the construction of C–O bonds and C–N bonds are also summarized. The catalytic activity of TSILs is enhanced by improving the synergy effect of different functional groups on anions and cations. It is expected that this minireview will provide the understanding of the current developments and perspective for practical CO₂ absorption and transformation by TSILs.     

离子液体谱学性质和热力学数据关联的新进展

离子液体的性质是其微观结构和相互作用的外在表现,与其应用密切相关.谱学手段能从分子水平上探测离子液体的微观环境和相互作用,近年来在定量关联或预测离子液体宏观性质方面发挥着越来越重要的作用.本文着重概述了红外光谱(IR)、拉曼光谱(Raman)、核磁共振波谱(NMR)和电子顺磁波谱(ESR)等常见谱学手段在定量关联离子液体及其溶液体系宏观性质方面的研究进展以及发展方向.     

Analytical developments and applications of ionic liquids for environmental studies

Ionic liquids (ILs) are considered advanced solvents with interesting properties that have led to remarkable improvements in the performance of analytical methods and their practical application. Analytical chemistry has profited from the evolution of ILs in diverse contexts, ranging from their applications in microextractions to uses as matrices for mass spectrometric determinations. Their use in sample preparation has meant significant improvements in terms of miniaturization and analytical performance, and given place to new techniques based on liquid-liquid and solid-phase extractions; the latter greatly driven forward by the combination of ILs with nanomaterials. Furthermore, electrodes have been prepared by combining ILs with different modern materials, significantly improving the sensitivity and selectivity of electroanalytical methods. Moreover, the implementation of ILs as additives to mobile and stationary phases in separation techniques has been proved to improve liquid and gas chromatography, as well as capillary electrophoresis, in terms of the number of analytes that can be efficiently separated and of the useful life of columns, representing also a promising alternative to environmentally dangerous organic solvents. Additionally, their application as matrix modifiers and as ion-pairing additives has introduced their use in mass spectrometry. In this review, the design and implementation of innovative and highly efficient analytical methods based on ILs for the sensitive and selective determination of diverse analytes in environmental matrices is described. Critical issues that have arisen from their application and future challenges in electrochemical, separation and preconcentration techniques based on these solvents are also presented.     

Convenient synthesis of imidazolium based dicationic ionic liquids

Research on Chemical Intermediates - A series of imidazolium based Dicationic Ionic Liquids (ILs) have been prepared and characterized successfully. Derivatives are prepared keeping the alkyl chain...     

Multi-Interactions in Ionic Liquids for Natural Product Extraction

Natural products with a variety of pharmacological effects are important sources for commercial drugs, and it is very crucial to develop effective techniques to selectively extract and isolate bioactive natural components from the plants against the background of sustainable development. Ionic liquids (ILs) are a kind of designable material with unique physicochemical properties, including good thermal stability, negligible vapor pressure, good solvation ability, etc. ILs have already been used in pharmaceuticals for extraction, purification, drug delivery, etc. It has been reported that multi-interactions, like hydrogen bonding, hydrophobic interactions, play important roles in the extraction of bioactive components from the plants. In this review, recent progress in the understanding of scientific essence of hydrogen bonding, the special interaction, in ILs was summarized. The extraction of various natural products, one important area in pharmaceutical, by conventional and functional ILs as well as the specific roles of multi-interactions in this process were also reviewed. Moreover, problems existing in bioactive compound extraction by ILs and the future developing trends of this area are given, which might be helpful for scientists, especially beginners, in this field.     

Application of ionic liquids in the microwave-assisted extraction of polyphenolic compounds from medicinal plants

Ionic liquids (ILs) solutions as solvents were successfully applied in the microwave-assisted extraction (MAE) of polyphenolic compounds from medicinal plants. ILs, its concentration and MAE conditions were investigated in order to extract polyphenolic compounds effectively from Psidium guajava Linn. (P. guajava) leaves and Smilax china (S. china) tubers. The results obtained indicated that the anions and cations of ILs had influences on the extraction of polyphenolic compounds as well as the ILs with electron-rich aromatic π-system enhanced extraction ability. Under the optimized conditions, the extraction yields of the polyphenolic compounds were in the range of 79.5-93.8% with one-step extraction, and meanwhile the recoveries were in the range of 85.2-103% with relative standard deviations (R.S.D.s) lower than 5.6%. Compared to conventional extraction procedures, the results suggested that the proposed method was effective and alternative for the extraction of polyphenolic compounds from medicinal plants. In addition, the extraction mechanisms and the structures of samples before and after extraction were also investigated. ILs solutions as green solvents in the MAE of polyphenolic compounds from medicinal plant samples showed a great promising prospect.     

Applications of ionic liquids in electrochemical sensors

Ionic liquids (ILs) are molten salts with the melting point close to or below room temperature. They are composed of two asymmetrical ions of opposite charges that only loosely fit together (usually bulky organic cations and smaller anions). The good solvating properties, high conductivity, non-volatility, low toxicity, large electrochemical window (i.e. the electrochemical potential range over which the electrolyte is neither reduced nor oxidized on electrodes) and good electrochemical stability, make ILs suitable for many applications. Recently, novel ion selective sensors, gas sensors and biosensors based on ILs have been developed. IL gels were found to have good biocompatibility with enzymes, proteins and even living cells. Besides a brief discussion of the properties of ILs and their general applications based on these properties, this review focuses on the application of ILs in electroanalytical sensors.     

Utility of ionic liquids in analytical separations

Ionic liquids (ILs), as separation media, have made significant contributions in the past decades in advancing research in gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). This review, covering reports published from the mid 1980s to early 2007, shows how ILs have been used so far in separation science, originally primarily as GC stationary phases and later as mobile phase additives (both millimolar and major percent levels) for LC and CE. Representative GC and LC chromatograms as well as CE electropherograms are shown. In addition, the very recent findings on the development of ionic liquids with surfactant properties and its applications for chiral and achiral analysis are discussed.     

离子液体的前沿、进展及应用

离子液体作为一类新型绿色介质,近年来获得了突飞猛进的发展.离子液体的多项应用研究正在进行中试或工业性试验,甚至已经进入产业化阶段.推动离子液体研究迅速发展的直接动力来源于国际社会对清洁生产、环境保护、循环经济的强烈愿望,以及离子液体本身的科学探索价值和巨大的应用潜力.离子液体不仅可替代传统有机溶剂或酸碱成功用作化工反应和分离的新介质,而且展示了作为新型磁性材料、纳微结构功能材料、润滑材料、航空航天推进剂等潜力,甚至有望成为食品和医药.     

Polarization of ionic liquid and polymer and its implications for polymerized ionic liquids: An overview towards a new theory and simulation

Ionic liquid (IL)-containing polymers garner attention for electrochemical applications. This article overviews recent experimental and theoretical studies of polymer electrolytes that would be likely to cultivate new theoretical and computational frameworks for IL-containing polymers. The first two sections outline the uniqueness of ILs that differentiates them from inorganic salts in polymers and explore deviation from the concept of the metaphor “room-temperature molten salt.” Such distinct properties include (1) large intrinsic dipole moment and electronic polarizability, (2) hydrogen bonding, (3) π-interactions, (4) a broad distribution of charges over the entire ion, and (5) the anisotropy of the ions. Moreover, the complexity of these properties substantially increases when the ions are polymerized. Indeed, their exceptional features would overcome the hurdle due to a trade-off between ionic conductivity and mechanical robustness in inorganic salt-doped polymers. Given these facts, the rest of the article focuses on emerging trends in the study of the dielectric response, phase separation, ion conductivity, and mechanical robustness of the polymer electrolytes, highlighting outstanding observations in experiments that may inspire existing theory and simulation. Our discussion also includes improving computational complexity for IL-containing polymers. To this end, recent machine learning studies that consider ILs and polymer liquids are presented.