Physicochemical properties of branched-chain dicationic ionic liquids

Environmental impact assessment of dicationic ionic liquids with ammonium-phosphonium cations and amino acid anions

Progress in the development of biodegradable or biobased ionic liquids (ILs) has led to the design of green compounds for several applications. Herein, four biocompatible dicationic ionic liquids (DILs) with ammonium-phosphonium cations and amino acid anions were synthesized and investigated their environmental impact. The structures of the DILs were confirmed by spectral analyses (1H, 13C and 31P NMR). Furthermore, physicochemical properties such as density, viscosity and refractive index were determined. Water content, bromide content and solubility were thereafter determined as the parameters needed for further studies. Subsequently, their antifeedant activity towards economically important pests of grain in storage warehouses: the granary weevil, the confused flour beetle, and the khapra beetle was examined, showing the dependence on structure. Moreover, selected DILs were investigated for toxicity towards white mustard, Daphnia magna, and Artemia franciscana to specify the environmental impact. These studies were complemented by understand the biodegradation of DILs by bacterial communities derived from soil at the agricultural land. The result was DILs with limited environmental footprints that have great potential for further application studies.

Physico-Chemical Properties of Magnetic Dicationic Ionic Liquids with Tetrahaloferrate Anions

A series of imidazolium-based symmetrical and asymmetrical dicationic ionic liquids (DcILs) with alkyl spacers of different length and with [FeCl3 Br]- as counter ion have been synthesized. The synthesized DcILs are characterized by using FTIR and Raman spectroscopy as well as mass spectrometry, along with single-crystal XRD analysis. Physicochemical properties such as solubility, thermal stability and magnetic susceptibility are also measured. These compounds show low melting points, good solubility in water and organic solvents, thermal stability, and paramagnetism. The products of molar susceptibility and temperature (χmol ⋅T) for the synthesized DcILs have been found between 4.05 to 4.79 emu mol-1  K Oe-1 and effective magnetic moment values have also been determined to be compared to that expected from the spin-only approximation.

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.

An X-ray photoelectron spectroscopy study of ionic liquids based on a bridged dicationic moiety

A series of imidazolium and pyridinium-based bridged dicationic ionic liquids have been analysed using X-ray photoelectron spectroscopy. The different electronic environments of the dications have been investigated and a robust fitting model for the carbon C1s region has also been developed. The relative positions of different C1s components and N1s of dications have been determined and their complex C1s photoemission spectra produced from both aromatic and aliphatic carbon states giving photoemission peaks in the binding energy range of 289.0–283.9 eV. A contemporary fitting approach has been applied to a different set of environments which allowing comparison of the binding energies of cationic components of imidazolium and pyridinium-based dicationic ionic liquids. The experimental stoichiometry of all the carbons and nitrogens have also been calculated from XP spectra of the dicationic ionic liquids.

Expanding the Chemical Space of Benzimidazole Dicationic Ionic Liquids

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts.

Thermal Stability of Ionic Liquids: Current Status and Prospects for Future Development

Ionic liquids (ILs) are the safest solvent in various high-temperature applications due to their non-flammable properties. In order to obtain their thermal stability properties, thermogravimetric analysis (TGA) is extensively used to analyze the kinetics of the thermal decomposition process. This review summarizes the different kinetics analysis methods and finds the isoconversional methods are superior to the Arrhenius methods in calculating the activation energy, and two tools—the compensation effect and master plots—are suggested for the calculation of the pre-exponential factor. With both parameters, the maximum operating temperature (MOT) can be calculated to predict the thermal stability in long-term runnings. The collection of thermal stability data of ILs with divergent cations and anions shows the structure of cations such as alkyl side chains, functional groups, and alkyl substituents will affect the thermal stability, but their influence is less than that of anions. To develop ILs with superior thermal stability, dicationic ILs (DILs) are recommended, and typically, [C4(MIM)2][NTf2]2 has a decomposition temperature as high as 468.1 °C. For the convenience of application, thermal stability on the decomposition temperature and thermal decomposition activation energy of 130 ILs are summarized at the end of this manuscript.

Parallel Ionic Liquid Semi-Packed Microfabricated Columns for Complex Gas Analysis

The paper presents a parallel micro gas chromatography approach using three ionic liquid semipacked columns. Switching from single column to multiple parallel columns with different selectivity enhances the power of compound identification without increasing the analysis time. The columns are fabricated using microelectromechanical systems (MEMS) technology containing an array of microfabricated pillars. The columns are 1 m-long and 240 μm-deep with four pillars per row. All columns were functionalized with ionic liquid stationary phases using a modified static coating technique and demonstrated the number of theoretical plates between 5000 and 8300 per meter. The chip performance was investigated with four different samples: (1) a mixture of C7-C30 saturated alkanes, (2) a multianalyte mixture consisting of 20 compounds ranging from 80 to 238 °C in boiling point, (3) a mixture of five organic chemicals with varying degrees of polarity, and (4) 46-compounds mixture containing all the chemicals in the first three samples. The individual columns separated 75%-100% of the first three samples but failed to distinguish all 46 compounds due to coeluting analytes; however, the parallel configuration provided more retention time information by which all the compounds in all samples were fully determined.

Synthesis, characterization and application of a non-flammable dicationic ionic liquid in lithium-ion battery as electrolyte additive

A novel dicationic room temperature ionic liquid, 1,1′-(5,14-dioxo-4,6,13,15-tetraazaoctadecane-1,18-diyl) bis(3-(sec-butyl)-1H-imidazol-3-ium) bis((trifluoromethyl)-sulfonyl) imide has been synthesized and fully characterized. Its thermal and electrochemical analyses along with transport properties have been studied. We propose it as a potential nominal additive to the commonly used conventional organic carbonate electrolyte mixture and study its adaptability in Lithium-ion batteries which are the prime power sources for ultraportable electronic devices. We have compared the performance characteristics of the full cells made without and with this ionic liquid. The cells comprise lithium nickel cobalt manganese oxide cathode, graphite anode and ethylene carbonate - dimethyl carbonate (1:1, v/v + LiPF₆) mixture electrolyte with nominal amount of ionic liquid as additive. The major concern with conventional electrolytes such as degradation of the materials inside batteries has been addressed by this electrolyte additive. Additionally, this additive is safer at relatively higher temperature. In its presence, the overall battery life is enhanced and it shows good cycling performance and coulombic efficiency with better discharge capacities (22% higher) after 100 cycles. Even after the increase in current rate from 10 mA/g to 100 mA/g, the cell still retains around 73% of capacity.

1, 1'-Sulfinyldiethylammonium Bis (Hydrogen Sulfate) as a Recyclable Dicationic Ionic Liquid Catalyst for the Efficient Solvent-free Synthesis of 3, 4-Dihydropyrimidin-2(1H)-ones via Biginelli Reaction

OBJECTIVE

A facile and efficient method for synthesis of 3, 4-dihydropyrimidin-2(1H)-ones via Biginelli reaction catalyzed by a novel dicationic Brönsted acidic ionic liquid, [(EtNH2)2SO][HSO4]2, has been successfully developed.

MATERIALS AND METHODS

3, 4-Dihydropyrimidin-2(1H)-ones were synthesized through one-pot condensation of aromatic aldehydes, ethyl acetoacetate, and urea under solvent-free conditions using [(EtNH2)2SO][HSO4]2 as a novel catalyst. The progress of the reaction was monitored by thin-layer chromatography (ethyl acetate / n-hexane = 1 / 5). The products have been characterized by IR, 1H NMR, 13C NMR, and also by their melting points.

RESULTS

In this research, a library of dihydropyrimidinone derivatives was synthesized via Biginelli reaction under solvent-free conditions at 120oC using [(EtNH2)2SO][HSO4]2 as a catalyst. Various aromatic aldehydes, as well as heteroaromatic aldehydes, were employed, affording good to high yields of the corresponding products and illustrating the substrate generality of the present method. In addition, the prepared dicationic Brönsted acidic ionic liquid can be easily recovered and reused.

CONCLUSION

1, 1'-Sulfinyldiethylammonium bis (hydrogen sulfate), as a novel dicationic ionic liquid, can act as a highly efficient catalyst for the synthesis of 3, 4-dihydropyrimidin-2(1H)-ones under solvent-free conditions.

Synthesis of novel functional ionic liquids and their application in biomass

A series of dicationic ionic liquids (ILs) including [PF6][(PYR)C4(MIM)][Cl], [PF6][(PYR)C4(PYR)][Cl], [PF6][(PYR)C5(MIM)][Cl], and [PF6][(PYR)C5(PYR)][Cl], and monocationic ILs including [(PYR)C4Cl][PF6], [(PYR)C5Cl][PF6], [(MIM)C2COOH][PF6] and [(PYR)C2COOH][PF6] were synthesized. Their thermal stability and melting points were determined. Their solubility with organic solvents and the miscibility with water were investigated. These functional ILs are hydrophilic at high temperatures and they are hydrophobic at low temperatures, which enable the effective isolation of the resulting reducing sugar. High yields of reducing sugar were obtained for corn stalk after 8 h (20.73%) and potato starch after 6 h (72.50%) by the treatment with the mixture of [PF6][(PYR)C4(PYR)][Cl] and [(PYR)C2COOH][PF6]. The reuse of dicationic and monocationic ILs was successfully performed and no significant reduction in yields of reducing sugar was observed. These functional ILs have important implications in the design of homogeneous and heterogeneous systems with water and organic solvents, which could be used to satisfy some specific applications.

Synthesis and Properties of Magnetic Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity

A series of unique tunable aryl-imidazolium magnetic ionic liquids (MILs) with dual acidity that contain both Brønsted and Lewis acidic sites (abbreviated as B-L MILs) were synthesized and characterized using nuclear magnetic resonance and mass spectrometry. Physical properties, such as thermal properties, magnetic susceptibility, and Brønsted and Lewis acidity, were measured. These properties were found to depend on the cation structure. These B-L MILs had good solubility in many organic solvents, good thermal stability, and low melting points, and exhibited magnet-like behavior. For these B-L MILs, the Brønsted acidity was measured using ultraviolet-visible (UV-Vis), and the Lewis acidity was measured using Fourier transform infrared spectroscopy (FTIR). The results showed that B-L MILs with an electron-withdrawing group in the aryl-imidazolium moiety had higher Brønsted acidity, whereas those with an electron-donating group had higher Lewis acidity. This type of ionic liquid, with both Brønsted and Lewis acidic sites, is expected to be a useful solvent and catalyst for organic reactions.

A flexible and convenient strategy for synthesis of ionic liquid bonded polysiloxane stationary phases

Ionic liquid bonded polysiloxanes (PILs) are a class of polysiloxanes whose side chains contain ionic liquid (IL) moieties. Considering their excellent selectivity and thermo-stability, PILs have great potentials in the development of polar stationary phases for gas chromatography. In this paper, a novel synthesis strategy for PILs is proposed to diversify PIL stationary phases and also facilitate the study on relationships between stationary phase structure and separation performances. The polysiloxane with imidazole groups at the side chains was synthesized firstly, and then these imidazole groups further reacted with halogenated compounds to produce various IL groups. Upon this, fifteen PIL stationary phases differing in IL content, IL group or combination of different IL groups have been synthesized and used to prepare capillary columns through static coating method. These columns have quite different general polarity indexes (the average value of all Rohrschneider-McReynolds constants in this paper) falling in a broad range from 218 to 717, and most columns have column efficiency values over 3000 plates/m. In addition, IL content, structure of the IL and combination of different IL groups have noticeable influences on interaction features of the stationary phases. After that, the separation performances of these PIL stationary phases were demonstrated by separating various mixed samples of aliphatic esters, dichloro-anilines, alcohols, aromatic amines, substituted alkanes, and so on. In order to reveal the relationship of interaction characteristics and separation performances, a set of indexes of contribution rates (CRs) is proposed. Based on CRs, the separation selectivity of the PIL stationary phases has been discussed in detail. The results indicate that there are significant differences in the separation selectivity not only between PILs and conventional polar stationary phases, but also among different PILs. All of these imply a family of practical PILs with special selectivity could be constructed upon this synthesis strategy.