Monocationic Ionic Liquids Research Articles

Widening the Stimuli-Responsiveness of Aqueous Biphasic Systems by Changing the Ionic Liquid Cation Basicity.

Herein we demonstrate the formation of new stimuli-responsive aqueous biphasic systems (ABS), able to respond simultaneously to temperature and pH, or just to one stimulus, therefore allowing the design of more sustainable separation processes. This dual behavior is achieved with ABS formed by mono- or dicationic protic ionic liquids as phase-forming components, being defined by the ionic liquid cation chemical structure or its basicity. While ABS comprising monocationic ionic liquids only respond to the effect of temperature, systems comprising dicationic ionic liquids are simultaneously affected by both temperature and pH variations. Dicationic ionic liquids are here identified as the key to unlock a double response to stimuli, which is due to the presence of two pKa values afforded by the cation. The reported findings contribute to increase the customizability of double stimuli-responsive ABS based on ionic liquids, whose development was up to date limited to ionic liquids bearing pH-responsive anions, opening the door towards the development of more sustainable separation processes.

High-performance dicationic ionic liquids based on imidazolium and quaternary ammonium for phenol extraction

Phenolic compounds serve as crucial chemical raw materials abundant in coal tar, so it is of great economic value to extract phenolic compounds from coal tar. Ionic liquids (ILs) are regarded as desirable extractants in this separation field due to considerable advantages over traditional methods. Compared to traditional mono-cationic ILs, dicationic ionic liquids (DILs) exhibit outstanding thermal stability and a wider operating temperature range. Our research focused on developing DILs based on typical imidazolium and quaternary ammonium structures for phenol separation, examining the impact of the methylene chain length between the cations on the extraction efficiency. Hydrogen bonding and π-π interactions between DILs and phenol were also investigated as driving forces in the extraction process. 1-methyl-3-(3-(trimethylammonio)propyl)-1H-imidazol-3-ium bromide ([MIMC3N111][Br]2) with a moderate chain length was selected as the optimal extractant due to its weaker coulomb force inside the DIL, facilitating stronger hydrogen bonding with phenol compared to the other two DILs. Under optimized conditions, [MIMC3N111][Br]2 exhibited the highest extraction efficiency of 96.03 % in model oil (toluene and phenol) with a phenol content of 200 g dm−3 and the DIL to phenol mole ratio was only around 0.3. [MIMC3N111][Br]2 also featured excellent recyclability, maintaining high extraction efficiency through multiple cycles. Importantly, its lower solubility in oil-phenol mixtures compared to mono-cationic ILs significantly reduced contamination of the oil phase. The DILs in this work can exhibit significant potential for separating phenolic compounds with certain advantages.

On the Moisture Absorption Capability of Ionic Liquids.

Due to their many attractive physicochemical properties, ionic liquids (ILs) have received extensive attention with numerous applications proposed in various fields of science and technology. Despite this, the molecular origins of many of their properties, such as the moisture absorption capability, are still not well understood. For insight into this, we systematically synthesized 24 types of ILs by the combination of the dimethyl phosphate anion with various types of alkyl group-substituted cyclic cations─imidazolium, pyrazolium, 1,2,3-triazolium, and 1,2,4-triazolium cations─and performed a detailed analysis of the dehumidification properties of these ILs and their aqueous solutions. It was found that these IL systems have a high dehumidification capability (DC). Among the monocationic ILs, the best performance was obtained with 1-cyclohexylmethyl-4-methyl-1,2,4-triazolium dimethyl phosphate, whose DC (per mol) value is 14 times higher than that of popular solid desiccants like CaCl2 and silica gel. Dicationic ILs, such as 1,1'-(propane-1,3-diyl)bis(4-methyl-1,2,4-triazolium) bis(dimethyl phosphate), showed an even better moisture absorption, with a DC (per mol) value about 20 times higher than that of CaCl2. Small- and wide-angle X-ray scattering measurements of eight types of 1,2,4-triazolium dimethyl phosphate ILs were performed and revealed that the majority of these ILs form nanostructures. Such nanostructures, which vary with the identity of the IL and the water content, fall into three main categories: bicontinuous microemulsions, hexagonal cylinders, and micelle-like structures. Water in the solutions exists primarily in polar regions in the nanostructures; these spaces function as water pockets at relatively low water concentrations. Since the structure and stability of the aggregated forms of the ILs are mainly governed by the interactions of nonpolar groups, the alkyl side chains of the cations play an important role in the DC and temperature-dependent equilibrium water vapor pressure of the IL solutions. Our experimental findings and molecular dynamics simulation results shed light on the moisture absorption mechanism of the IL aqueous solutions from a molecular perspective.

Wear mechanism of alloy steel under dicationic liquid lubricant with IL-grafted graphene oxide as an additive

A dicationic liquid (DIL) was synthesized and used as a base lubricant. IL-grafted graphene oxides (MGO) were manufactured as an additive to the DIL lubricant. Then, the MGO/DIL was applied as a lubricant for the surface contact between a stainless steel ball and bearing steel. The tribological performance of MGO/DIL was measured and compared to those from a monocationic liquid (MIL) based lubricant. The MGO/DIL lubricant produced better friction and wear performance at room temperature but poor wear at 100 °C. Through novel instrumentation techniques, it could be found that when DIL is exposed to air at higher temperatures, more oxygen is adsorbed into DIL, which accordingly reacts with underlying bearing steel, resulting in critical surface oxidation and wear.

Molecular insights into dicationic versus monocationic ionic liquids as a high hydrophobic alternative for the separation of phenol from waters

The hydrophobic nature of an extractant is particularly critical in the treatment of wastewater. Considering that dicationic ionic liquids (DILs) are likely to be more hydrophobic, a comparative study of the separation of phenol from waters using [NTf2]– based monocationic ionic liquids (MILs) and DILs is carried out both from experimental and theoretical analysis perspectives. Experimental results revealed that DILs exhibited superior extraction ability compared to MILs, with extraction efficiencies of 93.7% and 97.4% using [BMIM][NTf2] and [C6(MIM)2][NTf2]2 as extractants, respectively. The microscopic examination through theoretical calculations elucidated the higher hydrophobicity and extraction efficiency of DILs over MILs. The results indicated that the DIL showed stronger hydrophobicity than the MIL because the hydrogen bond strength between the DIL and water was lower than that of the MIL. Although the hydrogen bond strength between the DIL and phenol was lower than that of the MIL, the stronger van der Waals forces existed between DIL and phenol, so DIL was more efficient in extracting phenol. In addition, the experimental parameters were optimized to provide basic data for application, such as mass ratio of ILs to water, extraction time and temperature, pH, and initial phenol content. Finally, the DILs were recovered using rotary evaporation apparatus, and the results demonstrated that DILs had good recovery and reuse performance. In brief, this work could provide an effective method for the treatment of phenol-containing wastewater. And the revelation of molecular mechanism is expected to positively impact the design of high-performance task-specific ILs.

Unraveling the impact of mono- or di-cationic ionic liquids on sodium deoxycholate aggregation and their interactions with ciprofloxacin

The interaction study between drugs and surfactants grasps significant attention in the field of pharmacology and for the advancement in pharmaceutical formulations. In this study, a mixed micellar system composed of sodium deoxycholate and either mono- or di-cationic ionic liquids was proposed. The main objective was to evaluate the aggregation behaviour of NaDC in the presence of mono or di-cationic ionic liquids and its ability to interact with ciprofloxacin. Although mixed micellar systems using imidazolium-based monocationic ionic liquids have been actively researched, the potential of di-cationic ionic liquid has not yet been explored. Therefore, in the present work imidazolium-based monocationic ionic liquid ([C10(mIm)]Br) and corresponding di-cationic ionic liquid ([C10(mIm)2]2Br) with bromide as a common anion were synthesized and evaluated their effect on the aggregation behavior of sodium deoxycholate. The aggregation behaviour of these micellar and mixed micellar systems was evaluated using conductivity and fluorescence experiments by determining the critical micellar concentration. Additionally, dynamic light scattering experiments were conducted to comprehend the size of the aggregates that are formed, and zeta potential was measured to determine the surface charge of the micelles which in turn helps to determine the stability of the aggregates formed. The interaction study between micellar or mixed micellar systems with ciprofloxacin was carried out using UV–visible spectroscopy. The Benesi-Hildebrand equation was employed to scrutinize the interaction parameters of micellar and mixed micellar systems with CIP, revealing that the mixed micellar system containing [C10(mIm)]Br exhibited the greatest binding affinity towards CIP.

An efficient, selective, and solventless approach to carbamates in DBU-derived ionic liquids: Experimental and theoretical investigations

Herein, we report the synthesis of a diverse array of DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) based monocationic and dicationic ionic liquids with different inorganic and organic anions. All the synthesized ILs have been characterized by recording their 1H and 13C NMR spectra. The synthesized ILs have been utilized as catalysts in the carbamation of amines with dimethyl carbonate. A detailed study has been conducted to illuminate the possible mechanistic establishment by probing the role of catalysts played by the DBU and DBU-derived ionic liquids in the carbamation process. The attachment of the butyl group to the nitrogen of the DBU unit reversed the selectivity, which has been well established with the help of spectral techniques and theoretical (DFT) studies. The DBU-derived ionic liquids facilitated the N-methoxycarbonylation of amines over N-alkylation. Among all, the best carbamate yields were obtained in the presence of [BuDBU]Ala IL under optimized reaction conditions. The IL catalyst was efficiently reused five times without any significant catalytic loss. The current carbamation protocol possesses advantages like ease of setup, eco-friendly, catalytic reusability, and selectivity.

Using dicationic ionic liquids to upgrade the cytotoxicity and solubility of poorly water-soluble drugs

New dicationic ionic liquids (DcILs) based on carboxylic acid-derived, N-acetyl amino acid-derived or bromide anions, and ammonium cations were synthesized and characterized. DcILs were employed as co-solvents to improve the solubility of ibuprofen and ketoprofen belonging to BCS class II. These DcILs demonstrated to be less cytotoxic towards fibroblasts L929 cells and contributed to an augment in the solubility of both drugs when compared with monocationic ionic liquids (McILs). The cytotoxic profile of some of these ILs was established, and when the linker between two ammonium cations was an ether group or a short alkyl chain an IC50 higher than 200 mM for fibroblasts L929 cells was achieved.The anion structure showed to be a key factor in the solubility of both drugs, being the family of carboxylic acid-derived, the one that presented the most significant effect, followed by N-acetyl amino acid-derived and finally bromide. The two dimensional 1H1H– NOESY NMR spectra showed the interaction between the IL and the two oral drugs, responsible for the improvement of their solubility. The lipophilicity (logP) of ibuprofen and ketoprofen reduced in the presence of these new DcILs.

Evaluation of antimicrobial properties of monocationic and dicationic surface-active ionic liquids

In the present study, a series of monocationic and dicationic surface-active ionic liquids (SAILs) were synthesized and characterized. The structures of SAILs were confirmed by spectral analyses of 1H NMR and 13C NMR. Additionally, the thermal properties of the synthesized monocationic and dicationic SAILs were determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Nevertheless, the crucial part of this work is to confirm the strong relationship between the structure, surface activity, and biological action of newly SAILs on bacteria (both G(-) and G(+)) and fungi. The elongation of the alkyl chain or linker in the imidazolium cation results in a decrease in the minimum inhibitory concentration (MIC). Dicationic SAILs containing more than eight carbon atoms in the linker showed antimicrobial activity. In contrast, a cutoff effect was observed for their monocationic analog.

CO2 capture using dicationic ionic liquids (DILs): Molecular dynamics and DFT-IR studies on the role of cations.

Dicationic ionic liquids (DILs) have been shown to be useful as an effective solvent for the absorption of CO2. However, compared to monocationic ionic liquids (MILs), they have been less investigated for this application. Previous studies on MIL-CO2 systems have shown that anions play the main role in tuning CO2 capture, but the partial negative charge on the oxygens of CO2 may interact with cation centers and, especially, for DILs with two charge centers, the role of cations can be significant. Therefore, the current work focuses on how cation symmetry and the length of side chains affect interactions and also the dynamical and structural properties of DIL-CO2 systems using molecular dynamics simulation. In addition, the effect of CO2 on the infrared vibrational spectra of isolated ions and ion triplet (DIL molecules) was studied using density functional theory calculations and the observed red and blue shifts have been interpreted. The results indicated that symmetric cation with longer side chains tend to interact more strongly with CO2 molecules. It seems that increasing the length of the side chains causes more bending of the middle chain, and in addition to increasing the free fraction volume, it weakens the interaction between cations and anions, and as a result more interaction between gas and cation. The results of this work may contribute to the rational molecular design of DILs for CO2 capture, DIL-based gas sensors, etc.

Assessing the Suitability of a Dicationic Ionic Liquid as a Stabilizing Material for the Storage of DNA in Aqueous Medium.

The present study has been undertaken with an objective to find out a suitable medium for the long-term stability and storage of the ct-DNA structure in aqueous solution. For this purpose, the potential of a pyrrolidinium-based dicationic ionic liquid (DIL) in stabilizing ct-DNA structure has been investigated by following the DNA-DIL interaction. Additionally, in order to understand the fundamental aspects regarding the DNA-DIL interaction in a comprehensive manner, studies are also done by employing structurally similar monocationic ionic liquids (MILs). The investigations have been carried out both at ensemble-average and single molecular level by using various spectroscopic techniques. The molecular docking study has also been performed to throw more light into the experimental observations. The combined steady-state and time-resolved fluorescence, fluorescence correlation spectroscopy, and circular dichroism measurements have demonstrated that DILs can effectively be used as better storage media for ct-DNA as compared to MILs. Investigations have also shown that the extra electrostatic interaction between the cationic head group of DIL and the phosphate backbone of DNA is primarily responsible for providing better stabilization to ct-DNA, retaining its native structure in aqueous medium. The outcomes of the present study are also expected to provide valuable insights in designing new polycationic IL systems that can be used in nucleic acid-based applications.

How 1,n-Bis(3-alkylimidazolium-1-yl) Alkane Interacts with the Phospholipid Membrane and Impacts the Toxicity of Dicationic Ionic Liquids.

Ionic liquids based on doubly charged cations, often termed dicationic ionic liquids (DILs), offer robust physicochemical properties and low toxicity than conventional monocationic ionic liquids. In this design-based study, we used solid-state NMR spectroscopy to provide the interaction mechanism of two DILs, 1,n-bis(3-alkylimidazolium-1-yl) alkane dibromide ([C2n(C7-nIM)2]2+·2Br-, n = 1, 6), with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) phospholipid membranes, to explain the low toxicity of DILs toward HeLa, Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae cell lines. Dications with a short linker and long terminal chains cause substantial perturbation to the bilayer structure, making them more membrane permeabilizing, as shown by fluorescence-based dye leakage assays. The structural perturbation is even higher than [C12(MIM)]+ monocations, which carry a single 12-carbon long chain and exhibit a much higher membrane affinity, permeability, and cytotoxicity. These structural details are a crucial contribution to the design strategies aimed at harnessing the biological activity of ionic liquids.

Thermodynamics of aggregation and modulation of Rheo-Thermal properties of hydroxypropyl cellulose by imidazolium ionic liquids

Mixtures based on cellulose derivatives/ionic liquids (ILs) are potential viscosity modifiers for enhanced oil recovery (EOR). This paper investigates the thermodynamic of monocationic imidazolium ionic liquids (1-alkyl-3-methylimidazolium bromide, CnMIMBr) aggregation with hydroxypropyl cellulose (HPC) in the dilute regime and the modulation of its rheological and thermal properties in the semi-dilute regime. The outcomes showed that binding occurs by hydrophobic interactions between the alkyl chain of ILs and hydroxypropyl group on HPC and by ion–dipole interactions, and it is driven by entropy. The addition of ILs produced a significant increase in the HPC solutions' viscosity, which depends on the concentration and alkyl chain length of the ILs (n = 10, 12, 14, 16). Moreover, the presence of ILs produces an effect salt-in delaying the HPC phase separation. These findings highlight the role of ILs on the rheological and thermal properties of HPC, opening new possibilities for the design of new complex mixtures.

Thermal Decomposition, Low Temperature Phase Transitions and Vapor Pressure of Less Common Ionic Liquids Based on the Bis(trifuoromethanesulfonyl)imide Anion.

Four ionic liquids (ILs) based on the bis(trifluoromethanesulfonyl)imide (NTf2) anion were synthesized and characterized concerning their thermal stability, the occurrence of low temperature phase transitions and their volatility. All these physical quantities are highly important for possible applications. Both monocationic and dicationic ILs were considered. All ILs exhibit thermal stability exceeding 350 °C, an extremely high value, due to the presence of the NTf2 anion. Monocationic ILs can undergo crystallization, and they melt at 1 and 38 °C. On the contrary, dicationic ILs containing large positively charged ions display only a glass transition around −40 °C, without any crystallization or melting process; this fact is particularly important in view of the possibly low temperature applications of the dication ILs. The vapor pressure, pv, of the four ILs was measured by isothermal thermogravimetry in the temperature range between 250 and 325 °C; the lowest values of pv were obtained for the two dicationic liquids, suggesting that they are particularly well suited for high temperature applications. The vaporization enthalpy was calculated through the Clausius–Clapeyron equation and was found in the range between ~140 and ~180 kJ/mol depending on the specific IL.

Optimization and Kinetic Studies on Biodiesel Conversion from Chlorella vulgaris Microalgae Using Pyrrolidinium-Based Ionic Liquids as a Catalyst

This study describes the potential conversion of dried microalgae. Chlorella vulgaris (C. vulgaris) into fatty acid methyl ester (FAME) using the direct transesterification (DT) method and using ionic liquids (ILs) as a catalyst. In this work, the performance of monocationic IL, namely 1-butyl-1-methylpyrrolidinium bromide (IL 1), and dicationic IL, namely 1,4-bis(1-methylpyrrolidinium-1-yl) butane dibromide (IL 2), as catalysts was compared for DT of C. vulgaris under microwave irradiation. The results revealed that IL 2 showed a better performance in catalyzing the DT reaction by producing 87.9 mg/g% of FAME, while the use of IL 1 led to 74.3 mg/g% of FAME under optimum conditions. The kinetic study for direct transesterification of C. vulgaris showed that the reaction followed a first order kinetic reaction where the activation energies were calculated to be 22.2499 kJ mol−1 and 22.0413 kJ mol−1 for IL 1 and IL 2, respectively.

Thermal Kinetics of Monocationic and Dicationic Pyrrolidinium-Based Ionic Liquids.

This work presents an in-depth kinetic thermal degradation comparison between traditional monocationic and the newly developed dicationic ionic liquid (IL), both coupled with a bromide (Br−) anion by using non-isothermal thermogravimetric analysis. Thermal analyses of 1-butyl-1-methylpyrrolidinium bromide [C4MPyr][Br] and 1,4-bis(1-methylpyrrolidinium-1-yl)butane dibromide [BisC4MPyr][Br2] were conducted at a temperature range of 50–650 °C and subjected to various heating rates, which are 5, 10, 15, 20 and 25 °C/min. Thermogravimetric analysis revealed that dicationic IL, [BisC4MPyr][Br2] is less thermally stable compared to monocationic [C4MPyr][Br]. A detailed analysis of kinetic parameters, which are the activation energy (Ea) and pre-exponential factor (log A), was calculated by using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Starink. This study revealed that the average Ea and log A of [BisC4MPyr][Br2] are lower than [C4MPyr][Br], which may be contributed to by its low thermal stability. Conclusively, it proved that the Ea and log A of ILs are strongly related to the thermal stability of ILs.

Synthesis of functional dicationic ionic liquids for the treatment of lignocellulosic biomass.

Mono-cationic ionic liquids (MILs) have been widely utilized for the treatment of lignocelluloses. However, the hydrophilic property of MILs increases the difficulty of isolating sugars and their reuse, which limits their industrial application. In the present study, a series of dicationic ionic liquids (DILs) were synthesized with totally different di-cations and di-anions. An alternating miscibility of DILs with water was observed depending on the dealing temperature. The functional DILs exhibiting hydrophobic and acidic properties were investigated for the treatment of corn stalk. High yields of sugars were achieved as 27.8% and 31.6% with DIL3 and DIL4, respectively. Cellulosic materials were obtained as 74.3% and 77.8% with DIL1 and DIL2 and 61.2% and 65.7% with DIL3 and DIL4, respectively. Enzymatic reaction was successfully performed with cellulosic materials after the DIL treatment. DILs were recycled and reused with no significant reduction in sugar yields. Hydrophobic DILs are a potentially effective approach to enable the successful decomposition and degradation of lignocellulosic biomass.

Influence of alkyl chain length of monocationic ionic liquids towards pharmacological activities

In this present work, to synthesis alkyl and aryl substituted monocationic ionic liquids (ILs) of 1–benzyl–3–octadecylimidazolium bromide (ILa), 1–benzyl–3–octadecylbenzimidazolium bromide (ILb), 1–benzyl–3–ethylbenzimidazolium bromide (ILc), 1–benzyl–3–ethylimidazolium bromide (ILd) and 1–benzylpyridinium bromide (ILe), the synthesized ILs are structurally characterized using various physico–chemical, analytical and spectral (FT–IR, 1H & 13C NMR, EI-MS) studies. The synthesized ILs of 1–benzyl–3–ethylbenzimidazolium bromide (ILc), 1–benzyl–3–ethylimidazolium bromide (ILd) and 1–benzylpyridinium bromide (ILe) exhibited significant in vitro biological and antioxidant activities. Furthermore, the synthesized ILs (ILa– ILe) were tested for their in vitro cytotoxicity against human leukemia cancer cell line K–562, human ovarian cancer cell line SK–OV–3, human prostate cancer cell line DU–145 and human non-tumor cell line (normal fetal lung fibroblasts, MRC-5) by SRB assay protocol. The results indicate that 1–benzyl–3–octadecylimidazolium bromide (ILa) and 1–benzyl–3–octadecylbenzimidazolium bromide (ILb) showed remarkable toxicity against cancer cells and low toxicity against healthy cell line. These facts open the possibility of designing new nontoxic ionic liquids that can be used as active pharmaceutical ingredients in the liquid form.

Effect of Lithium-Ion on the Structural Organization of Monocationic and Dicationic Ionic Liquids.

In recent times, ionic liquid-based (ILs) electrolytic system has emerged as suitable alternative to the conventional organic solvent-based electrolytic system. However, since, anion of ILs is known to form aggregates in the presence of lithium-ions (Li+), and this can influence the transport properties of Li+ ion in a significant manner, it is, therefore, important to understand how lithium-ions influence the structure and dynamics of ILs. With this objective, in the present study, intermolecular interaction, structural organization, and dynamics of monocationic ILs (MILs) and dicationic IL (DIL) have been studied in the absence and presence of lithium salt. Specifically, for this purpose, two MILs, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([C3C1im][NTf2]), 1-hexyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([C6C1im][NTf2]), and a DIL, 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide ([C6(mim)2][NTf2]2) have been chosen in such a way that either the alkyl chain of MILs becomes equal or half of the spacer chain length of DIL. To understand the effect of the addition of lithium-ion on the structural organization of MILs and DIL, steady-state absorption and fluorescence spectroscopies, time-resolved fluorescence anisotropy and nuclear magnetic resonance (NMR) techniques have been used. Structural organization in the apolar and polar domains of ILs has been probed by following the rotational diffusion of suitably chosen solute in the concerned media through time-resolved fluorescence anisotropy (TRFA) measurements. TRFA studies have revealed that with the addition of Li+ ion, coordination between the Li+ ions and anions of MILs and DILs takes place in the ionic region leading to a change in the structural organization of the apolar regions of the respective medium. In fact, upon adding lithium-ions, a reduction in the packing of alkyl chains has also been observed for the MILs. However, not much change in the structural organization of the apolar region of the DIL has been observed when Li+ ion is added to it. In the presence of Li+ ions, a similar trend in the change of structural organization of polar regions for both MILs and DIL has been observed. Further, measurements of the self-diffusion coefficient through NMR have also supported the observation that Li+ ion also perturbs the nanostructural organization of the MIL in a significant manner than that it does for the DIL. The behavior of DIL in the presence of Li+ ion, as revealed by the present study, has been rationalized by considering the folded arrangement of DIL in the fluid-structure. Essentially, all of these investigations have suggested that the addition of lithium-ion significantly alters the microscopic behavior of MILs in comparison to that of DIL. The outcome of this study is expected to be helpful in realizing the potentials of these media as electrolytes in battery applications.

Heating Profile of Long Alkyl Chain Ionic Liquid Doped Solvents Under Ultrasound Irradiation

In this work, the heating profile of water, dimethyl sulfoxide (DMSO), acetonitrile (CH3CN) and ethanol (EtOH) and their solutions containing monocationic (CnMIMBr, n = 4, 6, 8, 10, 12, 14 and 16) and dicationic (di-CnMIMBr, n = 4, 6, 8 and 10) imidazolium-based ionic liquids (ILs) were evaluated under ultrasound irradiation. Similarly, ILs (CnMIMBr, n = 4, 8 and 14) with the BF 4 − anion and inorganic salts, such as NaBr and NaCH3CO2 were also evaluated. The results showed that water and DMSO have a linear heating profile; while CH3CN and EtOH have a logarithmic profile. In general, the IL-containing solutions heated up a little faster than the pure solvents, which indicates that the cationic moiety of the ILs did not cause notable changes in the heating profile of the solvents. The IL concentration and the consequent dissociation effects on this were not observed in any of the experimental conditions tested. The addition of NaBr and NaCH3CO2 changed the heating profile of EtOH, resulting in a linear profile. Additionally, our results confirmed that experimental parameters, such as irradiation amplitude and solution volume, significantly change the heating profile of solvents. Finally, under conventional heating and stirring (silent experiments), the heating profile of the pure solvents and the IL-containing solvents indicated that, under ultrasound, the cavitation process makes the heating faster and more efficient. Determination of the dissipated power reflected the solvent’s heating profile more than its heat capacity; therefore, the heating rate in ultrasound reveals the cavitation effects in the particular medium. These results are important because they show that the catalytic effects of ILs in chemical reactions or the solvent effects in micro extraction processes under ultrasound irradiation can be retained without raising the temperature and without decomposition of the ILs or products.