Dicationic Imidazolium Ionic Liquid Research Articles

Exploring how cation entropy influences electric double layer formation and electrochemical reactivity.

Electric double layers are crucial to energy storage and electrocatalytic device performance. While double layer formation originates in electrostatic interactions, electric double layer properties are governed by a balance of both electrostatic and entropic driving forces. Favorable ion-surface electrostatic interactions attract counterions to charged surfaces to compensate, or "screen," potentials, but the confinement of these same ions from a bulk reservoir to the interface incurs an entropic penalty. Here, we use a dicationic imidazolium ionic liquid and its monovalent analogue to explore how cation valence and entropy influence double layer formation and electrochemical reactivity using CO2 electroreduction as a model reaction. We find that divalent and monovalent cations display similar CO2 reduction kinetics but differ vastly in steady-state reactivity due to rapid electrochemically induced precipitation of insulating dicationic (bi)carbonate films. Using in situ surface-enhanced Raman scattering spectroscopy, we find that potential-dependent cation reorientation occurs at similar potentials between the two ionic liquids, but the introduction of a covalent link in the divalent cation imparts a more ordered double layer structure that favors (bi)carbonate precipitation. In mixed monovalent-divalent electrolytes, we find that the divalent cations dominate interfacial properties by preferentially accumulating at surfaces even at very low relative concentrations. Our findings confirm that ion entropy plays a key role in modulating local electrochemical environments. Furthermore, we highlight how double layer properties are sensitive to the properties of counterions that pay the lowest entropic penalty to accumulate at interfaces. Overall, we illustrate that ion entropy provides a new knob to tune reaction microenvironments and unveil how entropy plays a major role in modulating electrochemical reactivity in mixed ion electrolytes.

Novel MCM-41 Supported Dicationic Imidazolium Ionic Liquids Catalyzed Greener and Efficient Regioselective Synthesis of 2-Oxazolidinones from Aziridines and Carbon Dioxide

A type of MCM-41 supported dicationic imidazolium ionic liquid nanocatalyst has been synthesized and found to be competent for the synthesis of 2-oxazolidinones through the sustainable chemical conversion of CO2 with aziridines. It was shown that the highest efficiency was achieved in the cycloaddition of a series of aziridines and CO2 in the presence of a catalytic amount of the solid catalyst MCM-41@ILLaCl4 under mild conditions. Merits of this meticulously designed protocol are the use of a novel supported ionic liquid catalyst, the easy work-up process, good to excellent yields, a short reaction time, and purification without column chromatography. Overall, the present protocol of synthesizing 2-oxazolidinones under cocatalyst- and solvent-free conditions using MCM-41@ILLaCl4 is promising for industrial applications.

Effect of mono- and dicationic ionic liquids on the viscosity and thermogelation of methylcellulose in the semi-diluted regime

Thermoreversible hydrogels are suitable in food products in order to improve texture and in biomedical applications as drug delivery vehicles. The properties of hydrogels affect their performance in those applications. In this paper, it is presented the effect of mono- (CnMIMBr) and dicationic (Cn(MIM)2Br2) imidazolium ionic liquids (ILs) on the viscosity and gelation of methylcellulose (MC) using rheology, micro differential scanning calorimetric and small angle X-ray scattering (SAXS) techniques. Results show that the ILs affect the pattern of the sol-gel transition and display transition from the salt-out to the salt-in on the gelation temperature, decrease the gel strength and increase viscosity of MC solutions. This behavior can be explained by hydrophobic interaction between the ILs and the MC, which depends of the alkyl chain length of the ILs, type of ILs (conventional or bolaform) and the range of ILs concentration. In general, the presence of ILs decrease the MC gel strength, while dicationic ILs hampers their association on MC in comparison with monocationic ones. The findings highlight the role of ILs on gelation of MC opening possibilities for the design of new complex formulations.

XRD and ATR/FTIR investigations of various montmorillonite clays modified by monocationic and dicationic imidazolium ionic liquids

Three different montmorillonites (Mts) labeled K10, KSF and SWy-3 were analyzed by X-ray diffraction and ATR/FTIR spectroscopy. The XRD results enabled validation of the purification process of the studied clays. In the spectral regions 3800–2600 and 1800-1300 cm-1, the study of different intensity ratios of peaks assigned to the OH bending and stretching modes displayed the specific vibrational behavior of SWy-3 which is certainly influenced by a greater proportion of Na+ in its structure. Before analyzing the clays modified by ionic liquids, we characterized two imidazolium based ionic liquids (ILs) with anion I-: [EMIM+] [I−] monocationic ionic liquid and [M(CH₂) IM2+] [2I−] dicationic ionic liquid. The passage from [EMIM+] [I−] to [M(CH₂) IM2+] [2I−] reveals significant vibrational changes through various modes: ν(NH), rings ν(CC), rings ν(CN), ν(CH2(N)), ν(CH3(N)) in addition to anion interaction modes. When purified, these ionic liquids modify clays, the XRD analysis shows that the studied modified clays exhibited higher d-value increase with respect to the purified Mts, and the reflection peaks 2θ (°) of plane (001) were displaced towards lower values as a consequence of the ionic liquid intercalation process. ATR/FTIR spectra recorded in the spectral zone 4000-600 cm-1 indicated the appearance of new peaks and a significant intensity variation between clays in relation to the type of chosen ionic liquid. These vibrational changes are directly connected to the presence of ionic liquids in clays. XRD and ATR/FTIR investigations show a stronger effect of the [M(CH2) IM2+] [2I−] dicationic ionic liquid on the Mts than the monocationic ionic liquid and the SWy-3 Mt is more sensitive to monocationic and dicationic ionic liquids than K10 and KSF Mts.

Time-Resolved Characterization of Dynamic Tribochemical Processes for Dicationic Imidazolium Ionic Liquid

Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically stimulated gas emission mass-spectrometry (MSGE-MS). In comparison with similar monocationic imidazolium ionic liquids with short alkyl or long polyether side chains, the dicationic ionic liquid had a lower coefficient of friction on Ti6Al4V alloy and smoother behavior. The analysis of volatile decomposition products suggested multiple tribochemical reactions in which both anionic and cationic moieties are involved. The tribochemical degradation of cations was mainly through the detachment of the side and bridging chains from the imidazolium head groups. The absence of volatile products containing nitrogen implies that the imidazole group remained unchanged. Hydrogen and water desorption were attributed to the reactions of hydrogen fluoride being a product of anion degradation with titanium and titanium oxide, respectively.

ChemInform Abstract: Efficient Aerobic Oxidative Synthesis of Benzimidazoles with Fe(III) Based PEG1000 Dicationic Imidazolium Ionic Liquid/Toluene Temperature‐Dependent Biphasic System.

Abstract11 Benzimidazoles are prepared in toluene using a Fe(III)‐based PEG1000 dicationic imidazolium ionic liquid as catalyst.

Efficient Aerobic Oxidative Synthesis of Benzimidazoles with Fe(III) based PEG1000 Dicationic Imidazolium Ionic Liquid/toluene Temperature‐dependent Biphasic System

AbstractA green protocol for the synthesis of benzimidazoles with Fe(III) based PEG1000 dicationic imidazolium ionic liquid ([PEG1000mim2][FeCl4]2)/toluene temperature‐dependent biphasic system was described. Conformed by IR analysis, FeCl4− is the dominating anion species. It could be seen that aldehydes aryla mines and aromatic aldehydes bearing electron‐deficient group (Cl, Br, NO2) and electron‐rich groups (OH, N(CH3)2) on the aromatic rings gave good yields (78–96 %). Moreover, the Fe(III) based PEG1000 dicationic imidazolium ionic liquid could be recycled and reused without significant loss of catalytic activity after seven runs.

Solubilities of 1,1′-[1,2-Ethanediylbis(oxy-1,2-ethanediyl)]bis-[3-methyl-1H-imidazolium-1-yl] Dihexafluorophosphate in Water, Methanol, Ethanol, Dimethylformamide, Dimethyl Sulfoxide, and (Acetone + Water) Binary Solvent Mixtures

The chemical structure of a new gemini dicationic imidazolium ionic liquid, 1,1′-[1,2-ethanediylbis(oxy-1,2-ethanediyl)]bis-[3-methyl-1H-imidazolium-1-yl] dihexafluorophosphate ([C6O2(mim)2][PF6]2), was established by 1HNMR. The thermal stability of [C6O2(mim)2][PF6]2 was studied with differential scanning calorimetry and thermogravimetric analyses. With the use of the analytical stirred-flask method at atmospheric pressure, the solubilities of [C6O2(mim)2][PF6]2 in water, methanol, ethanol, dimethylformamide, dimethyl sulfoxide, and (acetone + water) binary solvent mixtures were measured from (283.00 to 323.00) K. The experimental data was correlated with the modified Apelblat equation.

Dicationic imidazolium ionic liquid modified silica as a novel reversed-phase/anion-exchange mixed-mode stationary phase for high-performance liquid chromatography.

A dicationic imidazolium ionic liquid modified silica stationary phase was prepared and evaluated by reversed-phase/anion-exchange mixed-mode chromatography. Model compounds (polycyclic aromatic hydrocarbons and anilines) were separated well on the column by reversed-phase chromatography; inorganic anions (bromate, bromide, nitrate, iodide, and thiocyanate), and organic anions (p-aminobenzoic acid, p-anilinesulfonic acid, sodium benzoate, pathalic acid, and salicylic acid) were also separated individually by anion-exchange chromatography. Based on the multiple sites of the stationary phase, the column could separate 14 solutes containing the above series of analytes in one run. The dicationic imidazolium ionic liquid modified silica can interact with hydrophobic analytes by the hydrophobic C6 chain; it can enhance selectivity to aromatic compounds by imidazolium groups; and it also provided anion-exchange and electrostatic interactions with ionic solutes. Compared with a monocationic ionic liquid functionalized stationary phase, the new stationary phase represented enhanced selectivity owing to more interaction sites.

Peroxopolyoxotungsten-based Ionic Hybrid as a Highly Efficient Recyclable Catalyst for Epoxidation of Vegetable oil with H2O2

utilizationefficiency, high catalytic activity, convenient recovery and good reuse ability.Key Words : Peroxopolyoxometalate, Dicationic imidazolium ionic liquid, Epoxidation, Vegetable oil, Hy-drogen peroxideIntroductionDue to the increasing environmental concerns and petro-leum supply severity, the use of biomass as raw material forpolymers, chemicals, fine chemicals and fuel applicationshas become an imperative issue in recent years. In thiscontext, Epoxidized vegetable oils, as one kind of vegetableoils derivatives, play an important role in industry of finechemicals, which can be used as PVC-plasticizers

Vibrational spectroscopic study of ionic liquids: Comparison between monocationic and dicationic imidazolium ionic liquids

In this study, we synthesised a dicationic ionic liquids labeled bis-methyl imidazolium methylidene bis (trifluoromethanesulfonyl) imide ([M(CH2)IM2+][2NTf2-]). The structure was identified by NMR. In order to characterise this ionic liquid, vibrational spectroscopy studies were performed by FTIR/ATR and FT-Raman spectroscopies. A comparative study was introduced by FTIR/ATR and FT-Raman spectroscopies, between our synthesised dicationic ionic liquid and a monocationic ionic liquid ([EMIM+][NTf2-]), where the anion and the cation are similar.FTIR/ATR spectra of dicationic ionic liquid are richer in modes especially in the spectral range of 3000cm−1. In the 1400–900cm−1 spectral region, the mode corresponding to the vibration of the NTf2- anion at 1040, 1140 and 1340cm−1 is very sensitive by the number of cation change. It was also the case for the peak at 1575cm−1 assigned to ring in-plane symmetric/anti-symmetric stretch CH2(N) and CH3(N)CN stretch. In the 4000–2800cm−1 spectral region, we observed few new peaks for [M(CH2)IM2+] comparatively with [EMIM+]; a splitting for the peak at 3105cm−1 and some wavenumber shifts for various modes.For the FT-Raman spectroscopy study, we realised our study in the spectral region 4000–0cm−1 while that of the monocationique sample is realised in the spectral region 1700–200cm−1. We observe in the common region 19 new peaks with the passage from the mono to dicationic, what is consequent. The impact of the passage from mono to dicationic is more important for the anion contribution spectral range (1400–300cm−1) than in the FTIR/ATR spectroscopy study. Other markers of differentiation between [M(CH2)IM2+] and [EMIM+] are observed for vibrational modes assigned to CH2(N) and CH3(N)CN stretch. We can also notice a contrast between the two spectroscopies: there are more active modes in FT-Raman than in FTIR/ATR spectroscopy.

Performances of ramie fiber pretreated with dicationic imidazolium ionic liquid

The chemical structure of a new gemini dicationic imidazolium ionic liquid, 3,3′-[1,2-ethanediylbis (oxy-2,1-ethanediyl)]-bis[1-methyl-imidazolium]-dibromide (PEG150-DIL) was established by 1H-NMR and elemental analyses. Then, PEG150-DIL was applied to pretreat ramie fiber. PEG150-DIL treated ramie fiber was characterized by FT-IR, XRD, DSC-TG and FE-SEM. Finally, the mechanical and dyeing properties of PEG150-DIL pretreated ramie fibers were studied. The optimum condition of PEG150-DIL modification was carried out at 100 °C for 30 min. The color strength increased obviously with the duration time and temperature of the PEG150-DIL. The tensile strength and strength retention of PEG150-DIL -treated ramie fibers decreased with the increase of pretreating time and temperature. The tensile strength retention was 86.20 % under optimal PEG150-DIL pretreating condition (100 °C, 30 min).

Solution and thermal behaviour of novel dicationic imidazolium ionic liquids

A new class of functionalised dicationic ionic liquids, containing a central cationic unit capped by a basic functionality (imidazole), has been synthesised. These salts have been characterised in isotropic solution using proton and 2D-NMR spectroscopy, and their thermal stability has been studied by DSC and TGA. All these novel salts contain the 1-(1-imidazolylmethyl)-3,5-di{1-(3'-octylimidazolylmethyl)}-benzene cation as a defining structural motif. Salts of both singly and doubly charged anions were prepared and, in particular, the selected monoanions (Br(-), [BF4](-), or [NTf2](-)) differ in size, shape and hydrogen-bonding ability, whereas the dianions differ in the nature of the spacer, such as 1,4-benzenedicarboxylate, 2,6-naphthalenedicarboxylate, 1,5- and 2,6-naphthalenedisulfonate, 1,4-butanedicarboxylate, and 1,6-hexanedicarboxylate. These ionic liquids exhibit the presence of different conformers in solution, whose distribution is affected by the nature of the anion. The nature of the anion also affects their thermal stability.