Influence of Structural Variations in Cationic and Anionic Moieties on the Polarity of Ionic Liquids

Macrocycle Unidirectional Transport Along a Linear Molecule by a Two-Step Chemical Reaction Sequence

Chemical systems displaying directional motions are relevant to the operation of artificial molecular machines. Herein we present the functioning of a molecule capable of transporting a cyclic species in a preferential direction. Our system is based on a linear, non-symmetric, positively charged molecule. This cation integrates into its structure two different reactive regions. On one side features a bulky ester group that can be exchanged by a smaller substituent; the other extreme contains an acid/base responsive moiety that plays a dual role, as part of the recognition motif and as a terminal group. In the acidic state, a dibenzo-24-crown-8 ether slides into the linear component attracted by the positively charged recognition site. It does this selectively through the extreme that contains the azepanium group, since the other side is sterically hindered. After base addition, intermolecular interactions are lost; however, the macrocycle is unable to escape from the linear component since the energy barrier to slide over the neutral azepane is too large. Therefore, a metastable mechanically interlocked molecule is formed. A second reaction, now on the ester functionality, exchanges the bulky mesityl for a methyl group, small enough to allow macrocycle dissociation, completing the directional transit of the ring along the track.

Cationic Imidazolium-Urethane-Based Poly(Ionic Liquids) Membranes for Enhanced CO2/CH4 Separation: Synthesis, Characterization, and Performance Evaluation

The escalating emissions of CO2 into the atmosphere require the urgent development of technologies aimed at mitigating environmental impacts. Among these, aqueous amine solutions and polymeric membranes, such as cellulose acetate and polyimide are commercial technologies requiring improvement or substitution to enhance the economic and energetic efficiency of CO2 separation processes. Ionic liquids and poly(ionic liquids) (PILs) are candidates to replace conventional CO2 separation technologies. PILs are a class of materials capable of combining the favorable gas affinity exhibited by ionic liquids (ILs) with the processability inherent in polymeric materials. In this context, the synthesis of the IL GLYMIM[Cl] was performed, followed by ion exchange processes to achieve GLYMIM variants with diverse counter anions (NTf2-, PF6-, and BF4). Subsequently, PIL membranes were fabricated from these tailored ILs and subjected to characterization, employing techniques such as SEC, FTIR, DSC, TGA, DMA, FEG-SEM, and CO2 sorption analysis using the pressure decay method. Furthermore, permeability and ideal selectivity assessments of CO2/CH4 mixture were performed to derive the diffusion and solubility coefficients for both CO2 and CH4. PIL membranes exhibited adequate thermal and mechanical properties. The PIL-BF4 demonstrated CO2 sorption capacities of 33.5 mg CO2/g at 1 bar and 104.8 mg CO2/g at 10 bar. Furthermore, the PIL-BF4 membrane exhibited permeability and ideal (CO2/CH4) selectivity values of 41 barrer and 44, respectively, surpassing those of a commercial cellulose acetate membrane as reported in the existing literature. This study underscores the potential of PIL-based membranes as promising candidates for enhanced CO2 capture technologies.

The role of urea on the dissolution of starch in NaOH-urea aqueous solutions

Potato starch can be dissolved in NaOH-urea aqueous solutions to form a stable and homogeneous mixture to initiate further modification. The mechanism for the formation of such a solution was investigated by examining the interactions between urea and starch, using rheological tests, ¹³C NMR, FTIR, and a novel Kamlet-Taft solvation parameter analysis. It was found that the optimized dissolution condition was in aqueous 10% w/w NaOH-14% w/w urea, under which 97.4% light transmission was achieved. This was due to dispersive forces between urea and starch without the presence of strong hydrogen bond based interactions. DSC results further showed that the subtle dissolving facilitation of urea might be attributed to the heat released during urea hydrate formation. Compared with conventional hydrothermal gelatinized starch, the starch-NaOH-urea aqueous dispersion exhibited better stability. This highlighted the role of urea in forming a 'bridge' to combine starch with water molecules. This reduces the tendency for starch aggregation via its hydrophobic components. Intrinsic viscosity and GPC analysis indicated that the degradation of starch molecules was significantly reduced. This work provides new insights into the role of urea in starch-NaOH-urea aqueous dispersion. This type of starch solvent formulation will have significant potential for further preparation of starch-based materials for various applications.

Thermoresponsive Ionic Liquid with Different Cation-Anion Pairs as Draw Solutes in Forward Osmosis

We synthesized various phosphonium- and ammonium-based ionic liquids (ILs), using benzenesulfonate (BS) and 4-methylbenzenesulfonate (MBS) to establish the criteria for designing an ideal draw solute in a forward osmosis (FO) system. Additionally, the effects of monocationic, dicationic, and anionic species on FO performance were studied. Monocationic compounds ([P₄₄₄₄][BS], [P₄₄₄₄][MBS], [N₄₄₄₄][BS], and [N₄₄₄₄][MBS]) were obtained in one step via anion exchange. Dicationic compounds ([(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], [(N₄₄₄₄)₂][BS], and [(N₄₄₄₄)₂][MBS]) were prepared in two steps via a Menshutkin SN₂ reaction and anion exchange. We also investigated the suitability of ILs as draw solutes for FO systems. The aqueous [P₄₄₄₄][BS], [N₄₄₄₄][BS], [N₄₄₄₄][MBS], and [(N₄₄₄₄)₂][BS] solutions did not exhibit thermoresponsive behavior. However, 20 wt% [P₄₄₄₄][MBS], [(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], and [(N₄₄₄₄)₂][MBS] had critical temperatures of approximately 43, 33, 22, and 60 °C, respectively, enabling their recovery using temperature. An increase in IL hydrophobicity and bulkiness reduces its miscibility with water, demonstrating that it can be used to tune its thermoresponsive properties. Moreover, the FO performance of 20 wt% aqueous [(P₄₄₄₄)₂][MBS] solution was tested for water flux and found to be approximately 10.58 LMH with the active layer facing the draw solution mode and 9.40 LMH with the active layer facing the feed solution.

Thermal Properties and Solvent Polarities of Mixed-Valence Ionic Liquids Containing Cationic Biferrocenylene Derivatives

Ionic liquids (ILs) containing cationic mixed-valence biferrocenylene derivatives were synthesized with an octanoyl or octyl substituent in each cation. Their melting points ranged between 25 and 39 °C, and the octanoyl derivatives exhibited higher melting points than the octyl derivatives. In addition, each IL exhibited a glass transition in the temperature ranging from -66 to -45 °C after melting. Their melting points were ∼10 °C higher than those of mononuclear octamethylferrocenium salts bearing the same substituents. The solvent polarity (E_T^N) and Kamlet-Taft parameters (π*, α, and β) of these dinuclear and mononuclear ILs were then examined. The dinuclear ILs bearing octanoyl substituents exhibited significant increases in E_T^N and π* and a decrease in α with the decreasing temperature, whereas the other ILs exhibited a significantly less pronounced temperature dependence. Finally, the intervalence charge-transfer (or charge-resonance) bands of the octanoyl dinuclear ILs exhibited red shifts with the decreasing temperature, which can be regarded as self-thermosolvatochromism.

Solvent-free continuous flow hydrogenation of N-methylpyrrolidone to N-methylpyrrolidine catalyzed by bimetallic Pt/V on HAP

The continuous flow hydrogenation of N-methylpyrrolidone which catalyzed by Pt/V/HAP (Pt/V molar ratio = 1 : 0.5) was achieved running for 100 h with solvent-free, and the N-methylpyrrolidine yield was above 85.21%.

Photoswitching studies of new photochromic ionic liquids studied in real time by in situ irradiation

In situ irradiation allowed us to study in detail the photostationary state of new photoswitchable bicationic azobenzenes.

The influence of the cation structure on the basicity-related polarity of ionic liquids

UV/Vis absorption data of (E)-4-(2-[5-{4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl}thiene-2-yl]vinyl)-2-(dicyano-methylene)-3-cyano-5,5-dimethyl-2,5-dihydrofuran (ThTCF) as a solvatochromic probe is applied to examine the anion coordination strength (e.g. of N(CN)₂, BF₄, PF₆, N(Tf)₂, CF₃COO) as a function of the cation structure of ionic liquids. Several 1-n-alky-3-methylimidazolium- and tetraalkylammonium CH₃-NR₃⁺-based ILs with different n-alkyl chain lengths (R = -C₄H₉, -C₆H₁₁, -C₈H₁₇, -C₁₀H₂₁) are considered. UV/Vis absorption data of ThTCF show subtle correlations with hydrogen bond accepting (HBA) ability-related measurands such as Kamlet-Taft β, Freire's E_HB, and Laurence β₁ parameter as a function of anion and cation structure. The different influence of the n-alkyl chain length of imidazolium- and tetraalkylammonium-based ILs on the dipolarity and HBA strength is confirmed by comparison with the ¹⁴N isotropic hyperfine coupling constants (A_iso) of a positively (CATI) and negatively charged spin probe (TSKCr) of TEMPO-type [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] and quantum chemically derived dipoles of the cations. The A_iso values correlate with the absorption energy of ThTCF and E_HB, but in different ways depending on the anion or charge of the spin probe. In a final discussion of the β, E_HB, and β₁ scales in relation to ThTCF, the importance of the molar concentration N of ionic liquids for the physical significance of the respective parameters is discussed.

Determination of physicochemical properties of ionic liquids by gas chromatography

Over the years room temperature ionic liquids have gained attention as solvents with favorable environmental and technical features. Both chromatographic and conventional methods afford suitable tools for the study of their physicochemical properties. Use of gas chromatography compared to conventional methods for the measurement of physicochemical properties of ionic liquids have several advantages; very low sample concentrations, high accuracy, faster measurements, use of wider temperature range and the possibility to determine physicochemical properties of impure samples. Also, general purpose gas chromatography instruments are widely available in most laboratories thus alleviating the need to purchase more specific instruments for less common physiochemical measurements. Some of the main types of physicochemical properties of ionic liquids accessible using gas chromatography include gas-liquid partition constants, infinite dilution activity coefficients, partial molar quantities, solubility parameters, system constants of the solvation parameter model, thermal stability, transport properties, and catalytic and other surface properties.

The physical significance of the Kamlet–Taft π* parameter of ionic liquids

The Kamlet–Taft dipolarity/polarizability parameters π* for various ionic liquids were determined using 4-tert-butyl-2-((dicyanomethylene)-5-[4-N,N-diethylamino)-benzylidene]-Δ3-thiazoline and 5-(N,N-dimethylamino)-5′-nitro-2,2′-bithiophene as solvatochromic probes.

Study on the synthesis of dual-chain ionic liquids and their application in the extraction of flavonoids

Ionic liquids, as tuneable, highly soluble, non-flammable, non-volatile and reusable extractants, have attracted extensive attention in the extraction of flavonoids from plants. In the present work, novel dual-chain imidazolium-derived ionic liquids were synthesized by a simple and efficient method and characterized (NMR spectroscopy, thermal stability, viscosity, conductivity, and polarity). Then, the imidazolium ionic liquids with different cation were used in the microwave-assisted extraction of flavonoids from Pinus massoniana Lamb. The results showed that the ionic liquid [Bmbim]Br, with a relatively low viscosity, conductivity and π* as well as a relatively large β, offered the best extraction efficiency and selectivity for flavonoids. Subsequently, the parameters of the extraction procedure for flavonoids were optimized as follows: extraction temperature of 80 °C, extraction time of 60 min, microwave power of 300 W, solid-liquid ratio of 1:20, and [Bmbim]Br solution concentration of 1.0 mol/L. The extraction yield of total flavonoids was 41.07 mg/g. Finally, a recovery method of the ionic liquid had been demonstrated, and the recovery rate of ionic liquid was 73.14%.

Complementary interpretation of ET(30) polarity parameters of ionic liquids

Reichardt's empirical ET(30) polarity parameter has been established as appropriate polarity scale for ionic liquids. In this study, the relationships of ET(30) of ionic liquids with the empirical Kamlet-Taft polarity parameters α (hydrogen bond donating ability), β (hydrogen bond accepting ability) and π* (dipolarity/polarizability) as well as Catalán's parameter set SA (solvent acidity), SB (solvent basicity), SP (solvent polarizability) and SdP (solvent dipolarity) are examined by means of multiple square correlation analyses. Several subtasks were carried out to address this main concern. First, the influence of anion structure on ET(30) polarity parameters for various ionic liquids are investigated by use of nine differently substituted pyridinio phenolate betaine dyes of the Reichardt type. It is assumed that halide anions can have an effect on the ET(30) parameter. In the second part, the Kamlet-Taft π* parameters have been independently determined for several protic ionic liquids using 4-tert-butyl-2-(dicyanomethylene)-5-[4-(diethylamino)-benzylidene]-Δ3-thiazoline (Th) and N,N-diethyl-4-nitroaniline (DENA) to show the impact of the hydrogen bond donating ability of the IL on the actual π* values as function of probe. α and SA values have been measured using the dicyano-bis(1,10-phenanthroline) iron(ii) complex (Fe) as HBD probe. Finally, the newly determined Reichardt ET(30), Kamlet-Taft and Catalán parameters of ionic liquids were used in addition to literature data to prove correlations of ET(30) with α and π* as well as of ET(30) with SA and SdP. Linear correlations of SdP with the molar concentration of the ionic liquid are highlighted.

Solvation properties of protic ionic liquids and molecular solvents

Ionic liquids (ILs) are highly tailorable solvents with many potential applications. Knowledge about their solvation properties is highly beneficial in the utilization of ILs for specific tasks, though for many ILs this is currently unknown.

Solvation properties of protic ionic liquid–molecular solvent mixtures

In this study, we have investigated the solvation properties of binary mixtures of PILs with molecular solvents. The selected binary solvent systems are the PILs ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) combined with either water, methanol, acetonitrile or DMSO.

Cellulose in Ionic Liquids and Alkaline Solutions: Advances in the Mechanisms of Biopolymer Dissolution and Regeneration

This review is focused on assessment of solvents for cellulose dissolution and the mechanism of regeneration of the dissolved biopolymer. The solvents of interest are imidazole-based ionic liquids, quaternary ammonium electrolytes, salts of super-bases, and their binary mixtures with molecular solvents. We briefly discuss the mechanism of cellulose dissolution and address the strategies for assessing solvent efficiency, as inferred from its physico-chemical properties. In addition to the favorable effect of lower cellulose solution rheology, microscopic solvent/solution properties, including empirical polarity, Lewis acidity, Lewis basicity, and dipolarity/polarizability are determinants of cellulose dissolution. We discuss how these microscopic properties are calculated from the UV-Vis spectra of solvatochromic probes, and their use to explain the observed solvent efficiency order. We dwell briefly on use of other techniques, in particular NMR and theoretical calculations for the same purpose. Once dissolved, cellulose is either regenerated in different physical shapes, or derivatized under homogeneous conditions. We discuss the mechanism of, and the steps involved in cellulose regeneration, via formation of mini-sheets, association into “mini-crystals”, and convergence into larger crystalline and amorphous regions. We discuss the use of different techniques, including FTIR, X-ray diffraction, and theoretical calculations to probe the forces involved in cellulose regeneration.

Establishing Predictive Models for Solvatochromic Parameters of Ionic Liquids

The use of ionic liquids (ILs) in applications ranging from catalysis to reaction media in organic synthesis has been successfully demonstrated in several cases. For any given IL application, fundamental properties, such as viscosity, thermal stability, and toxicity have to be considered. Another property of interest is the polarity, which is a crucial indicator of solvent effects on chemical processes. Given the near-infinite combinations of cations and anions, experimental determination of solvatochromic parameters, such as the hydrogen-bond acidity and basicity, and dipolarity-polarizability is prohibitive. To address this, we evaluate the utility of alternative schemes based on parameters derived from COSMO-RS (COnductor-like Screening MOdel for Real Solvents) computations. The scheme is applied to a large library of yet-to-be-synthesized ionic liquids, to identify promising candidates for applications in biomass dissolution.

A Robust Fungal Allomelanin Mimic: An Antioxidant and Potent π-Electron Donor with Free-Radical Properties that can be Tuned by Ionic Liquids

Developing effective strategies to increase the chemical stability and to fine-tune the physico-chemical properties of melanin biopolymers by rational control of π-electron conjugation is an important goal in materials science for biomedical and technological applications. Herein we report that poly-1,8-dihydroxynaphthalene (pDHN), a non-nitrogenous, catechol-free fungal melanin mimic, displays a high degree of structural integrity (from MALDI-MS and CP/MAS ¹³ C NMR analysis), a strong radical scavenging capacity (DPPH and FRAP assays), and an unusually intense EPR signal (g=2.0030). Morphological and spectral characterization of pDHN, along with deassembly experiments in ionic liquids, indicated amorphous aggregates of small globular structures with an estimated stacking distance of 3.9 Å and broadband absorption throughout the visible range. These results indicate that DHN-based melanins exhibit a high structural integrity and enhanced antioxidant and free-radical properties of potentially greater biomedical and technological relevance than for typical indole-based eumelanins.

High throughput approach to investigating ternary solvents of aqueous non-stoichiometric protic ionic liquids

The use of ionic liquids (ILs) is limited for many applications due to their cost and/or viscosity. An efficient solution is to make mixtures of ILs with molecular solvents. However, it is well known that there are a large number of possible cation and anion combinations resulting in ILs, and this becomes a vast number when these are then combined with a molecular solvent. Therefore, we need structure-property relationships to design new IL-molecular solvent systems. In this work we have applied high throughput methods to investigate IL containing solutions to provide systematic data of a broad compositional space. We have principally focused on the surface tension, apparent pH and liquid nanostructure to identify potential self-assembly and protein stabilizing ability of solvent systems. Non-stoichiometric and aqueous IL-solvents were prepared in a high-throughput manner based on a deliberate experimental design approach such that 26 samples were prepared for each cation-anion-water combination. A selection of 8 protic ionic liquids (PILs) were used as starting materials, comprising ethanol-, ethyl-, butyl-, and pentylammonium cations combined with formate, acetate and nitrate anions. This resulted in a total of 208 different solvent systems. The measured solvent properties showed different trends in base-rich and acid-rich solvent combinations. Surface tensions of base-rich samples exhibited a relatively linear relationship with increasing excess amine, while acid-rich samples were more dominantly affected by the change in water content. Liquid nanostructure of acid-rich samples was retained upon water dilution, whereas a significant SAXS peak shift towards lower scattering angles was observed in the presence of excess amines, indicating larger nanosized aggregates were forming. The design of experiment approach used here is considered to be applicable to any multi-component solvent compositional space due to its suitability in using small data sets to cover large compositional spaces, and hence can be employed to decrease the time and sample quantities required.

Microheterogeneity in Ionic Liquid Mixtures: Hydrogen Bonding, Dispersed Ions, and Dispersed Ion Clusters

Mixtures of ionic liquids (ILs) having a common ion but differing in the identity of the anion or cation represent highly interesting media. By varying the composition, one can successfully modulate specific physicochemical, structural, and biological properties. The molecular interactions (coulombic, hydrogen-bonding, van der Waals, and π–π intermolecular forces) that determine the three-dimensional structure of pure ILs can indeed be modified by the addition of another IL. In this context, we present here a 1H NMR, Fourier transform (FT)-IR, thermogravimetric, and solvatochromic study of the structural features of IL binary mixtures based on a common imidazolium cation ([CnC1im]+) and anions of different size and hydrogen-bond acceptor ability. For each mixture, the analyses were carried out at different molar ratios of the two components.

Spectroscopic, photochromic and kinetic behavior of photo conversion of Aberchrome 540™ in an ionic liquid media

The photo-bleaching reaction of the chemical actinometer, Aberchrome 540™, is reported for the first time in a series of ionic liquids (ILs). This fulgide in its C-form undergoes an opening reaction to yield its E-form, when it is irradiated with UV light at wavelengths >400 nm. The magnitude of bleaching was monitored spectrophotometrically and their kinetics evaluated, obtaining first-order rate constants (k_obs). The results obtained in different ILs suggest that changes in the rate constants (k_obs) of the opening reaction of Aberchrome 540™ are mainly governed by weaker interactions such as coulombic (π* parameter) and Van der Waals interactions (δ_H², parameter). In addition, the photochemical fatigue resistance was also studied in ILs media and compared with conventional solvents (benzene, toluene, etc.). In particular, we found that three different tendencies dependent on the ILs used exist. The first group of ILs where the reversibility of the fulgide is favored (for example, [Bmim][BF₄], [Bmim][PF₆] and [Bmim][OTf]), behaviour similar to conventional solvents. The second group corresponds to ILs where photo reversibility is partial; and finally, other group of ILs that prevented photo reversibility. It is proposed that depending on the ILs used, the stabilization of different forms of the fulgide can be controlled, thus resulting important in terms of choosing the appropriate ILs for a specific photochemical reaction.

Activation of Electrophile/Nucleophile Pair by a Nucleophilic and Electrophilic Solvation in a SNAr Reaction

Nucleophilic aromatic substitution reactions of 4-chloroquinazoline toward aniline and hydrazine were used as a model system to experimentally show that a substrate bearing heteroatoms on the aromatic ring as substituent is able to establish intramolecular hydrogen bond which may be activated by the reaction media and/or the nature of the nucleophile.

Metal-Free One-Pot Four-Component Cascade Annulation in Ionic Liquids at Room Temperature: Convergent Access to Thiazoloquinolinone Derivatives

An efficient, eco-friendly, and highly convergent one-pot route to privileged thiazoloquinolinone derivatives has been developed via four-component cascade coupling (4CCC) of α-enolic dithioesters, cysteamine/2-aminothiophenols, aldehydes, and cyclic 1,3-diketones in recyclable [EMIM][EtSO₄] ionic liquid at room temperature for the first time. The reaction proceeds via a N,S-acetal formation, Knoevenagel condensation, aza-ene reaction, imine-enamine/keto-enol tautomerization, and intramolecular N-cyclization cascade sequence. The merit of the protocol is highlighted by its efficacy of forming consecutive five new bonds (two C-C, two C-N, and one C-S) and two rings with all reactants being efficiently utilized. The operational simplicity, sustainability, mild conditions, excellent yields, tolerance of wide functional groups, and avoidance of expensive/toxic reagents are additional attributes to this domino four-component protocol. Notably, the products were easily separated from the ionic liquid, and thus the ionic liquid obtained was reused four times without considerable loss of any activity.

Mechanisms ruling the partition of solutes in ionic-liquid-based aqueous biphasic systems - the multiple effects of ionic liquids

In the past decade, the remarkable potential of ionic-liquid-based aqueous biphasic systems (IL-based ABSs) to extract and purify a large range of valued-added biocompounds has been demonstrated. However, the translation of lab-scale experiments to an industrial scale has been precluded by a poor understanding of the molecular-level mechanisms ruling the separation or partition of target compounds between the coexisting phases. To overcome this limitation, we carried out a systematic evaluation of specific interactions, induced by ILs and several salts used as phase-forming components, and their impact on the partition of several solutes in IL-based ABSs. To this end, the physicochemical characterization of ABSs composed of imidazolium-based ILs, three salts (Na2SO4, K2CO3 and K3C6H5O7) and water was performed. The ability of the coexisting phases to participate in different solute-solvent interactions (where "solvent" corresponds to each ABS phase) was estimated based on the Gibbs free energy of transfer of a methylene group between the phases in equilibrium, ΔG(CH2), and on the Kamlet-Taft parameters - dipolarity/polarizability (π*), hydrogen-bonding donor acidity (α) and hydrogen-bonding acceptor basicity (β) - of the coexisting phases. Relationships between the partition coefficients, the phase properties expressed as Kamlet-Taft parameters and COSMO-RS descriptors were established, highlighting the ability of ILs to establish specific interactions with given solutes. The assembled results clearly support the idea that the partition of solutes in IL-based ABSs is due to multiple effects resulting from both global solute-solvent and specific solute-IL interactions. Solute-IL specific interactions are often dominant in IL-based ABSs, explaining the higher partition coefficients, extraction efficiencies and selectivities observed with these systems when compared to more traditional ones majorly composed of polymers.

The effect of varying the anion of an ionic liquid on the solvent effects on a nucleophilic aromatic substitution reaction

Variety of ionic liquids with different anions used as solvents for a nucleophilic aromatic substitution reaction.

A closer look into deep eutectic solvents: exploring intermolecular interactions using solvatochromic probes

Kamlet Taft solvatochromic parameters, namely the hydrogen-bond acidity, hydrogen-bond basicity and dipolarity/polarizability and E_TN parameters of a wide range of DESs composed of cholinium chloride, dl-menthol and a quaternary ammonium salt ([N₄₄₄₄]Cl), and corresponding ILs are here presented.

Dual function of amino acid ionic liquids (Bmim[AA]) on the degradation of the organophosphorus pesticide, Paraoxon®

The degradation of Paraoxon using Bmim[AA] ILs, is reached with a higher efficiency and without an extra nucleophile.

Introducing the Bipolar Solvent Media Using the Aqueous Mixtures of Amino Acid Anion-Based Ionic Liquids

To carry out a chemical reaction between the reactants with largely different polarities, it becomes important to have a reaction medium that possesses both the polar and nonpolar solvation environments. In an attempt to explore the reaction media with such unique polarity properties, the present study provides a thorough understanding of the bipolar solvent media using the aqueous mixtures of amino acid anion-based ionic liquids. The highly polar behavior of the binary mixtures used in the study has been ascribed to the pure ionic liquid state. However, the less polar solvation shells have been attributed to the presence of a neutral form of the anions. Addition of water in the amino acid anion-based ionic liquids causes the protonation of a certain fraction of the anions of the ionic liquids, resulting into the formation of a less polar nonionic protonated form along with the highly polar natural anionic form. This results into the formation of two solvation spheres with different polarities, which can be seen very clearly from the presence of two absorption bands (lower wavelength absorption band and higher wavelength absorption band) in the UV-vis absorption spectrum of Reichardt's E_T(30) dye and two emission bands (lower wavelength emission band and higher wavelength emission band) in the fluorescence emission spectrum of C481 dye. The values of the E_T^N polarity parameter corresponding to the two solvation shells having different polarities have been calculated from the deconvoluted absorption spectra of the Reichardt's E_T(30) and were analyzed in three amino acid anion-based ionic liquids. Generation of the neutral form of anions in the aqueous mixtures formed via a protonation transfer reaction has been confirmed by the ¹H NMR spectroscopy and UV-vis absorption spectrum of 18DHAQ dye. The study also establishes that the Reichardt's E_T(30) dye can be used as a valid polarity probe to study the solvatochromic behavior of the binary mixtures of amino acid-based ionic liquids.

Simple organic structure directing agents for synthesizing nanocrystalline zeolites

The synthesis of ZSM-5 and beta zeolites in their nanosized form has been achieved by using simple alkyl-substituted mono-cationic cyclic ammonium cations as OSDA molecules.

The synthesis of the ZSM-5 and beta zeolites in their nanosized form has been achieved by using simple alkyl-substituted mono-cationic cyclic ammonium cations as OSDA molecules. The particular combination of a cyclic fragment and a short linear alkyl-chain group (preferentially C₄) within the monocationic OSDA molecules allows directing the crystallization of nanosized zeolites with excellent solid yields (above 90%). Interestingly, the formation of the nanosized ZSM-5 and beta zeolites mostly depends on the size and nature of the cyclic fragment of the OSDA molecule, resulting in all cases in nanocrystalline solids with homogeneous distributions of particle sizes (∼10–25 nm) and controlled Si/Al molar ratios (∼15–30). The achieved nanosized ZSM-5 and beta zeolites have been extensively characterized by different techniques to study their physico-chemical properties, such as chemical composition, pore accessibility or Brønsted acidity, among others. Moreover, the catalytic properties of the nanosized ZSM-5 and beta zeolites have been evaluated for different chemical reactions, including methanol-to-olefins (MTO) in the case of ZSM-5, and alkylation of benzene with propylene to obtain cumene and oligomerization of light olefins to liquid fuels in the case of beta, observing in all cases improved catalytic activity and product selectivity towards target products when compared to related catalysts.

Polarity of tetraalkylammonium-based ionic liquids and related low temperature molten salts

Solvatochromic measurements and ¹H NMR spectroscopy have been used to investigate the overall polarity of tetraalkylammonium based ionic liquids and low temperature molten salts.

Understanding positive and negative deviations in polarity of ionic liquid mixtures by pseudo-solvent approach

Physico-chemical properties of liquid mixtures in general display large deviations from linear behaviour, arising out of complex specific and non-specific intermolecular interactions. The polarity of liquid mixtures displaying large positive and negative deviations can be minimized and linear mixing can be achieved in liquids using a pseudo-solvent methodology. The work described herein is designed to investigate the influence of different physical parameters on the linear pseudo-solvent composition in ionic liquid mixtures. For this purpose, we have determined the deviations from linearity, ΔE values (defined as given by ) for binary mixtures of a variety of ionic liquids, including two molecular solvents, DMSO and formamide. Firstly, the investigations were carried out in three 1-butyl-3-methylimidazolium cation based aprotic ionic liquids and the roles of anionic structure and hydrogen bond acceptor basicities (β values) of the ionic liquids were determined. The influence of the cationic structure, i.e., the hydrogen bond donor acidity (α values) and non-associative nature of the ionic liquids, was determined using C2-methylated analogs, 1-butyl-2,3-dimethylimidazolium cation based ionic liquids. The role of the protic nature of ionic liquids was studied in two protic ionic liquids, viz., 1-methylimidazolium formate and 1-methylimidazolium acetate. The effects of the temperature, pseudo-solvent structure and solvatochromic probe structure on the ΔE values were also explored.