Ionic Liquid Research Articles

Physico-chemical Study of Surface Active Ionic Liquid (SAIL) in Aqueous Inulin Solutions: Density and Speed of Sound Measurements

Colloidal formulations of surface active ionic liquid (SAIL) have substantial benefit as efficient carrier mainly for therapeutic/pharmaceutical agents. In this regard, density (ρ) and speed of sound (u) have been employed to evaluate the diverse interactions/association behaviour of greener SAIL tetrabutylammonium dodecylsulphate (TBADS) (0.222 to 2.2 mmol kg-1) in aqueous inulin solutions (0.0, 0.2 and 0.3% w/w) at five different temperatures ranging from 293.15 K to 313.15 K. The volumetric and acoustic parameters viz. isentropic compressibility (κs), apparent molar volume (Vφ) and compressibility (κs,φ), intermolecular free length (Lf), relative association (RA), specific acoustic impedance (Z) and molar sound number ([U]) have been calculated by using density (ρ) and speed of sound (u) values. The existence of hydrophilic/hydrophobic interactions for TBADS in aqueous inulin solution is suggested by the variations in volumetric parameters, which further supported by various calculated acoustic parameters. Thus, the interactional outcomes can offer implications that stabilized inulin in the presence of SAILs and can be utilized for the optimal biotic actions.

Introduction of a new cobalt-containing Lewis acidic ionic liquid catalyst for the reduction of nitroaromatic compounds and aldehydes and one-pot reductive acetylation of arylaldehydes

Introduction of a new cobalt-containing Lewis acidic ionic liquid catalyst for the reduction of nitroaromatic compounds and aldehydes and one-pot reductive acetylation of arylaldehydes

Correction to “Life Cycle Thinking-Based GREENNESS Framework for Advancing Green Chemistry: Case Study with Typical Ionic Liquids for Cellulose Dissolution and Regeneration”

Correction to “Life Cycle Thinking-Based GREENNESS Framework for Advancing Green Chemistry: Case Study with Typical Ionic Liquids for Cellulose Dissolution and Regeneration”

Exploring the Influence of Ionic Liquid Anion Structure on Gas-Ionic Liquid Partition Coefficients of Organic Solutes Using Machine Learning.

This article presents an in-depth investigation into the influence of anionic structures of ionic liquids (ILs) on gas-ionic liquid partition coefficients (log K) of organic solutes in three ILs. While the primary objective was to examine whether there is a relationship between the molecular structure of the IL anion component and log K, additionally it was looked at whether the molecular descriptors of the anion in the relationships encode possible molecular interactions during the miscibility and partitioning in the IL. The research involves the compilation of data series of experimental log K values, where the cation component is constant. Such representative data series were obtained for three solutes─benzene, cyclohexane, and methanol─in three ILs with a uniform cationic component of methylimidazoliums. Using multiple linear regression models enhanced with machine learning techniques, the relationship between anionic structures and log K values was successfully quantified and modeled. Systematically selected molecular descriptors describing the anion structure show that in the case of methanol log K is strongly dependent on hydrogen bonds and Coulomb-dipolar interactions with the anion component, while in the case of benzene and cyclohexane the dispersion forces of the anion component are dominant. The outlier analysis and data interpretation highlight the need for extensive experimental data. The results confirm the initial hypothesis and provide valuable information on the role of the structure of the anionic component in determining the partitioning behavior of organic solutes. This knowledge is important for the design and optimization of ILs for specific applications, particularly as solvents in various industrial processes. The research also provides useful information about molecular interactions taking place in the interfaces of IL and organic additives in complex liquid media such as multicomponent electrolyte solutions, for example in energy storage applications.

Stretchable conducting polymer PEDOT:PSS treated with hard‐cation‐soft‐anion ionic liquid designed from molecular modeling

AbstractPEDOT:PSS, an ionic polymer mixture of positively‐charged poly‐3,4‐ethylenedioxythiophene (PEDOT+) and negatively‐charged poly‐styrenesulfonate (PSS−), is a water‐processable and environmentally‐benign organic semiconductor and electrochemical transistor, which plays a key role in organic (bio)electronic devices. However, pristine PEDOT:PSS films form 10‐to‐30‐nm granular domains, where conducting‐but‐hydrophobic PEDOT‐rich cores are surrounded by hydrophilic‐but‐insulating PSS‐rich shells. Such morphology makes PEDOT:PSS water‐soluble and thermally stable but very poor in conductivity. A tremendous amount of effort has been made to enhance the conductivity of PEDOT:PSS by restoring the extended conduction network of PEDOT. Recently, remarkable ~5000‐fold improvements of conductivity have been achieved by mixing PEDOT:PSS with proper ionic liquids (ILs). In a series of free energy estimations using density functional theory calculation and molecular dynamics simulation, we have demonstrated that the classic hard‐soft acid–base (or cation‐anion) principle of chemistry plays an important role in such improvements. Ion exchange between PEDOT+:PSS− and A+:X− ILs helps PEDOT+ to decouple from PSS− and to grow into large‐scale conducting domains of π‐stacked PEDOT+ decorated by IL anions X−. Thus, the most spontaneous decoupling between soft (hydrophobic) PEDOT+ and hard (hydrophilic) PSS− would be induced by strong interaction with soft anions X− and hard cations A+, respectively. Such hard‐cation‐soft‐anion principles have led us to design ILs containing extremely hydrophilic (i.e., protic) cations and hydrophobic anions. Not only they indeed improve the conductivity of PEDOT:PSS but also enhance its stretchability as well. In summary, our modeling offered molecular‐level insights on the morphological, electrical, and mechanical properties of PEDOT:PSS and a molecular‐interaction‐based enhancement strategy for intrinsically stretchable conductive polymers.

Capture and in-situ conversion of low-concentration CO2 over robust poly(ionic liquid)@porous carbon nanocomposites under green, co-catalyst- and solvent-free conditions

The development of advanced materials with dual functionalities for the capture of low-concentration CO2 and its in-situ conversion into value-added chemicals under mild and green conditions holds significant practical importance. In this study, we present a facile pyrolysis of fluid precursors followed by an in-situ polymerization strategy for preparing poly(ionic liquid)@porous carbon nanocomposites (PIL-Brx@Zn-CTM), which possess multiple active sites including Lewis acidic Zn2+, Lewis basic N, and nucleophilic Br– groups. Subsequently, we investigate their potential application in the efficient capture and conversion of low-concentration CO2 into cyclic carbonates. The influence of PIL-Brx@Zn-CTM structures and technological conditions on the cycloaddition reaction between low-concentration CO2 (15 % CO2 and 85 % N2) and epichlorohydrin was examined. The PIL-Br1.0@Zn-CTM nanocomposite was determined to be the most suitable catalyst, resulting in a 94 % yield of chloropropene carbonate with 99 % selectivity under mild, co-catalyst-, and solvent-free conditions. Furthermore, the reusability of PIL-Br1.0@Zn-CTM and its substrate scope were investigated. The PIL-Br1.0@Zn-CTM exhibited sustained high activity without a significant decrease after seven cycles of reuse, and it also demonstrated excellent catalytic activity for cycloaddition reactions involving low-concentration CO2 with various substituted epoxides. Finally, a mechanism for the cycloaddition reaction catalyzed by the PIL-Brx@Zn-CTM nanocomposite was proposed.

Solution Processable Metal-Organic Frameworks: Synthesis Strategy and Applications.

Metal-organic frameworks (MOFs), constructed by inorganic secondary building units with organic linkers via reticular chemistry, inherently suffer from poor solution processability due to their insoluble nature, resulting from their extensive crystalline networks and structural rigidity. The ubiquitous occurrence of precipitation and agglomeration of MOFs upon formation poses a significant obstacle to the scale-up production of MOF-based monolith, aerogels, membranes, and electronic devices, thus restricting their practical applications in various scenarios. To address the previously mentioned challenge, significant strides have been achieved over the past decade in the development of various strategies aimed at preparing solution-processable MOF systems. In this review, the latest advance in the synthetic strategies for the construction of solution-processable MOFs, including direct dispersion in ionic liquids, surface modification, controllable calcination, and bottom-up synthesis, is comprehensively summarized. The respective advantages and disadvantages of each method are discussed. Additionally, the intriguing applications of solution-processable MOF systems in the fields of liquid adsorbent, molecular capture, sensing, and separation are systematically discussed. Finally, the challenges and opportunities about the continued advancement of solution-processable MOFs and their potential applications are outlooked.

Synthesis of New Xanthene and Acridine Derivatives from Cyclohexan-1,3-dione and the Study of their Antiproliferative Activities

Background: Ionic immobilized liquids and multi-component reactions are integral to green chemistry, facilitating the synthesis of biologically active compounds, such as xanthene and acridine derivatives. These approaches have garnered significant attention in recent years. Objective: The aim of this study was to synthesize novel xanthene and acridine derivatives with diverse substituents and heterocyclic rings. Furthermore, the research sought to evaluate their anticancer activity against various cancer cell lines and analyze their structure-activity relationships (SAR) to determine how structural modifications impact their biological effectiveness. Method: The core compounds in this study were synthesized from cyclohexane-1,3-dione and triethoxymethane under two distinct reaction conditions. The first involved the use of a solvent with either Et₃N or NH₄OAc as a catalyst, while the second employed a solvent-free approach using an ionic liquid catalyst (ILs). Results: The anti-proliferative activity of all synthesized compounds was evaluated against six selected cancer cell lines, revealing that many compounds exhibited significant inhibitory effects. Furthermore, their inhibitory potential against tyrosine kinases and Pim-1 kinases was assessed, along with an investigation of their mechanism of action on tyrosine kinases. Conclusion: The anti-proliferative activity of the newly synthesized compounds was evaluated against six cancer cell lines. Many of the compounds exhibited strong inhibitory effects not only against the tested cancer cell lines but also against tyrosine kinases and Pim-1 kinases.

An Expedient Approach for the Regioselective Synthesis of Fully Functionalized and Highly Substituted N‐Methyl‐1,4‐Dihydropyridines Using an Ionic Liquid Catalyst

AbstractA facile and highly efficient protocol has been developed for the synthesis of extensively functionalized, fully substituted N‐methyl‐1,4‐dihydropyridines. This approach is a one‐pot pseudo‐three‐constituent cyclo‐condensation of aromatic aldehydes with (E)‐N‐methyl‐1‐(methylthio)‐2‐nitroethenamine (NMSM). This reaction presumably entails the Knoevenagel reaction followed by Michael addition and regioselective N‐cyclization with removing methanethiol and producing two C─C bonds and one C─N bond. The key advantages of this strategy include an optimized reaction time, achieving moderate to excellent yields, a straightforward experimental procedure, and the use of the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate [(EMIM)Ac] as the catalyst. The resulting derivatives were well characterized by IR, 1H NMR, 13C NMR, and HRMS.

Ionic Liquid–Catalyzed Annulation of Biomass-Derived Alkyl Lactates: Time-Dependent Tunable Synthesis of Bioactive Dihydroquinoxalines and Quinoxalines

Ionic Liquid–Catalyzed Annulation of Biomass-Derived Alkyl Lactates: Time-Dependent Tunable Synthesis of Bioactive Dihydroquinoxalines and Quinoxalines

Thermal Responsiveness of 1,2,4-Triazolium-Based Poly(ionic liquid)s and Their Applications in Dye Extraction and Smart Switch.

Triazoliums are a family of five-membered heterocyclic cations that contain three nitrogen and two carbon atoms. In contrast to the widely studied imidazolium cations, triazoliums are less explored. In terms of the chemical structure, triazolium replaces a carbon atom in the imidazolium cation ring with an electron-withdrawing nitrogen atom, which makes the triazolium more polarized. Among the many physical properties, the thermal responsiveness of triazoliums is of particular interest to us but has been rarely investigated. In this contribution, we prepared a series of 1,2,4-triazolium-based poly(ionic liquid)s (PILs) with varying alkyl substituents and counteranions and studied their thermal-responsive behavior. We found that 1,2,4-triazolim-based PILs with a polymeric backbone structure similar to that of polyimidazoliums exhibited opposite thermal phase transition processes in solvents. For example, methyl-substituted 1,2,4-triazolium-based PILs exhibited an upper-critical-solution-temperature (UCST)-type phase transition in methanol when the counterion was I- and a lower-critical-solution-temperature (LCST)-type phase transition in acetone when the counterion was PF6 -. The thermal responsiveness was reversible and concentration-dependent. Interestingly, the thermal response of 1,2,4-triazolim-based PILs could be retained in the organogel form, which was applied in the pretreatment of anion-containing organic waste liquids and temperature-controlled "smart" switches.

Novel application of citric acid based natural deep eutectic solvent in drilling fluids for shale swelling prevention

Swelling of shale in clastic reservoirs poses a significant challenge, causing instability in wellbores. Utilizing water-based drilling mud with shale inhibitors is preferable for environmental reasons over oil-based mud. Ionic liquids (ILs) have garnered interest as shale inhibitors due to their customizable properties and strong electrostatic features. However, widely used imidazolium-based ILs in drilling fluids are found to be toxic, non-biodegradable, and expensive. Deep Eutectic Solvents (DES), considered a more economical and less toxic alternative to ILs, still fall short in terms of environmental sustainability. The latest advancement in this field introduces Natural Deep Eutectic Solvents (NADES), renowned for their genuine eco-friendliness. This study explores NADES formulated with citric acid (as a Hydrogen Bond Acceptor) and glycerine (as a Hydrogen Bond Donor) as additives in drilling fluids. The NADES based drilling mud was prepared according to API 13B-1 standards and their efficacy was compared with KCl, imidazolium based ionic liquid, and Choline Chloride: Urea-DES based mud. A thorough physicochemical characterization of the in-house prepared NADES is detailed. The research evaluates rheological, filtration and shale inhibition properties of the mud, demonstrating that NADES enhanced the yield point to plastic viscosity ratio (YP/PV), reduced mudcake thickness by 26%, and decreased filtrate volume by 30.1% at a 3% concentration. Notably, NADES achieved an impressive 49.14% inhibition of swelling and improved shale recovery by 86.36%. These outcomes are attributed to NADES’ ability to modify surface activity, zeta potential, and clay layer spacing which are discussed to understand the underlying mechanism. This sustainable drilling fluid promises to reshape the drilling industry by offering a non-toxic, cost-effective, and highly efficient alternative to conventional shale inhibitors, paving the way for environmentally conscious drilling practices.

Chitosan modified with an ionic liquid with two imidazolium rings for efficient removal of reactive black 5

Chitosan modified with an ionic liquid with two imidazolium rings for efficient removal of reactive black 5

Ionic Conductivity and Aggregation Behavior of N,N-Dimethylethanolammonium Carboxylate Protic Ionic Liquids in Aqueous, Ethanolic, and Acetonitrile Solutions

Ionic Conductivity and Aggregation Behavior of N,N-Dimethylethanolammonium Carboxylate Protic Ionic Liquids in Aqueous, Ethanolic, and Acetonitrile Solutions

Computational Advances in Ionic Liquid Applications for Green Chemistry: A Critical Review of Lignin Processing and Machine Learning Approaches.

The valorization and dissolution of lignin using ionic liquids (ILs) is critical for developing sustainable biorefineries and a circular bioeconomy. This review aims to critically assess the current state of computational and machine learning methods for understanding and optimizing IL-based lignin dissolution and valorization processes reported since 2022. The paper examines various computational approaches, from quantum chemistry to machine learning, highlighting their strengths, limitations, and recent advances in predicting and optimizing lignin-IL interactions. Key themes include the challenges in accurately modeling lignin's complex structure, the development of efficient screening methodologies for ionic liquids to enhance lignin dissolution and valorization processes, and the integration of machine learning with quantum calculations. These computational advances will drive progress in IL-based lignin valorization by providing deeper molecular-level insights and facilitating the rapid screening of novel IL-lignin systems.

Sustainable Synthesis of New Antioxidants from Hydroxytyrosol by Direct Biocatalytic Esterification in Ionic Liquids.

Hydroxytyrosol (HT) is a nutraceutical compound, mainly found in the fruit, leaves and waste from the olive oil industry, known for exhibiting one of the highest antioxidant activities among molecules of natural origin. To harness this bioactivity in cosmetics, pharmaceuticals and the food industry, it is essential to modify the hydrophilicity of HT to enhance its compatibility with lipid-based mixtures. This chemical modification must be carried out with high selectivity to avoid compromising its radical scavenging activity. This work presents a highly efficient and selective approach to perform the biocatalytic esterification of free fatty acids (FFAs) of different alkyl chain lengths with HT in a reaction medium based on the SLIL [C12mim][NTf2]. By using a 1:2 (mol/mol) HT:FFA mixture of substrates, the HT-monoester derivative was obtained up to 77% yield after 2 h at 80 °C. The optimized molar ratio of substrates, combined with the ability to recover the SLIL for further reuse, significantly reduces waste accumulation compared to other reported strategies and results in a more sustainable approach as demonstrated by different green metrics. The antioxidant activity of HT-monoester products was fully maintained with respect to that presented by the natural HT, being stable for at least 3 months at 4 °C, as demonstrated by the DPPH and FRAP antioxidant analysis.

Choline geranate (CAGE): A multifaceted ionic liquid for drug delivery

Ionic liquids, organic salts in a liquid state below 100 °C, have traditionally been associated with industrial applications. Recent research has introduced a new generation of ionic liquids, designed from biocompatible ions, to enable applications in drug delivery. Here, I provide a historical perspective, development status and applications of a leading example of biocompatible ionic liquids, a salt of Choline And Geranic acid (CAGE). Since its first report in 2014, CAGE has opened multiple drug delivery applications including transdermal, oral, buccal, sustained release, tissue ablation, periodontitis and hand hygiene, among others. CAGE-based products have been tested in more than 200 patients through multiple Phase 1 and Phase 2 clinical studies, including successful use in a Phase 2 clinical study in Atopic Dermatitis patients. CAGE became the first ‘drug delivery ionic liquid’ to enter into clinical trials. This article summarizes the key fundamental and translational aspects of CAGE as pertained to its use in drug delivery.

Robust and Reversible Thermal/Electro‐Responsive Supramolecular Polymeric Adhesives via Synergistic Hydrogen‐Bonds and Ionic Junctions

Adhesive conducting elastomers are rising materials towards cutting‐edge applications in wearable and implantable soft electronics. Yet, engineering the conductive adhesives with robust and tunable interfacial bonding strength is still in its infancy stage. We herein identify a structurally novel supramolecular polymer scaffold, characterized by synergistic coexistence of hydrogen‐bonding (H‐bonding) interactions and electrostatic ionic junctions, endowing the robust and tunable elastic conducting adhesives with remarkable thermal/electro‐responsive performance. H‐bonding association and electrostatic interaction play orthogonal yet synergistic roles in the strong supramolecular adhesive formation, serving as the leveraging forces for opposing both cohesion and adhesion energy. To do so, six‐arm star‐shaped random copolymers P(DAP‐co‐Thy‐co‐MBT)6 are strategically designed, bearing H‐bonding PDAP (poly(diaminopyridine acrylamide)) and PThy (poly(thymine)) segments, which can form hetero‐complementary DAP/Thy H‐bonding association, along with conductive poly(ionic liquid)s segment: PMBT, (poly(1‐[2‐methacryloylethyl]‐3‐methylimidazolium bis(trifluoromethane)‐sulfonamide)). DAP/Thy H‐bonding association, along with electrostatic ionic interaction, can yield dual supramolecular forces crosslinked polymeric networks with robust cohesion energy. Moreover, coexistence of poly(ionic liquid)s can impact and interfere the configuration of H‐bonding association, liberate more free DAP and Thy motifs to form H‐bonds towards substrate, affording strong surface adhesion in a synergistic manner. This work demonstrates a significant forward step towards potential adhesives devoted to hybrid electronic devices.

Robust and Reversible Thermal/Electro-Responsive Supramolecular Polymeric Adhesives via Synergistic Hydrogen-Bonds and Ionic Junctions.

Adhesive conducting elastomers are rising materials towards cutting-edge applications in wearable and implantable soft electronics. Yet, engineering the conductive adhesives with robust and tunable interfacial bonding strength is still in its infancy stage. We herein identify a structurally novel supramolecular polymer scaffold, characterized by synergistic coexistence of hydrogen-bonding (H-bonding) interactions and electrostatic ionic junctions, endowing the robust and tunable elastic conducting adhesives with remarkable thermal/electro-responsive performance. H-bonding association and electrostatic interaction play orthogonal yet synergistic roles in the strong supramolecular adhesive formation, serving as the leveraging forces for opposing both cohesion and adhesion energy. To do so, six-arm star-shaped random copolymers P(DAP-co-Thy-co-MBT)6 are strategically designed, bearing H-bonding PDAP (poly(diaminopyridine acrylamide)) and PThy (poly(thymine)) segments, which can form hetero-complementary DAP/Thy H-bonding association, along with conductive poly(ionic liquid)s segment: PMBT, (poly(1-[2-methacryloylethyl]-3-methylimidazolium bis(trifluoromethane)-sulfonamide)). DAP/Thy H-bonding association, along with electrostatic ionic interaction, can yield dual supramolecular forces crosslinked polymeric networks with robust cohesion energy. Moreover, coexistence of poly(ionic liquid)s can impact and interfere the configuration of H-bonding association, liberate more free DAP and Thy motifs to form H-bonds towards substrate, affording strong surface adhesion in a synergistic manner. This work demonstrates a significant forward step towards potential adhesives devoted to hybrid electronic devices.

Material Aspects of Thin-Film Composite Membranes for CO2/N2 Separation: Metal-Organic Frameworks vs. Graphene Oxides vs. Ionic Liquids.

Thin-film composite (TFC) membranes containing various fillers and additives present an effective alternative to conventional dense polymer membranes, which often suffer from low permeance (flux) and the permeability-selectivity tradeoff. Alongside the development and utilization of numerous new polymers over the past few decades, diverse additives such as metal-organic frameworks (MOFs), graphene oxides (GOs), and ionic liquids (ILs) have been integrated into the polymer matrix to enhance performance. However, achieving desirable interfacial compatibility between these additives and the host polymer matrix, particularly in TFC structures, remains a significant challenge. This review discusses recent advancements in TFC membranes for CO2/N2 separation, focusing on material structure, polymer-additive interaction, interface and separation properties. Specifically, we examine membranes operating under dry conditions to clearly assess the impact of additives on membrane properties and performance. Additionally, we provide a perspective on future research directions for designing high-performance membrane materials.