Quaternary Ammonium Ionic Liquids Research Articles

Dialkoxy functionalized quaternary ammonium ionic liquids as potential electrolytes and cellulose solvents

A series of new ionic liquids, based on dialkoxy-functionalized quaternary ammonium cations {side chains: 1 = CH3, 1O1 = CH3OCH2, 1O2 = CH3OC2H4, 2O2 = C2H5OC2H4; cations: [N11,1O1,1O2], [N11,1O1,2O2], [N11,1O2,1O2], [N11,1O2,2O2] and [N11,2O2,2O2]}, with BF4−, (CF3SO2)2N− (NTf2) and CH3CO2− (OAc) as counteranions, have been prepared and characterized. Their basic properties, such as spectroscopic characteristics, melting point, glass transition temperature, thermal stability, electrochemical window, density, refractive index, viscosity and conductivity, were measured and comparatively studied. The incorporation of two flexible alkoxy chains makes the quaternary ammonium salts highly qualified to be low-viscous and high-conductive room temperature ILs, and even some of them have significantly better fluidity than the popular imidazolium ILs with a similar molecular weight, e.g.[N11,1O1,2O2]BF4 (151 cP and 2.11 mS cm−1, Mw: 249) vs.[HMIm]BF4 (220 cP and 1.2 mS cm−1, Mw: 256) at 25 °C. The electrochemical windows of these ILs were evaluated up to 5.5 V. In addition, the dialkoxy OAc ILs were found to have excellent solvent power for cellulose under mild conditions, e.g. a solution of 18 wt% microcrystalline cellulose in [N11,2O2,2O2]OAc at 80 °C. By precipitation with water, the dissolved cellulose (I crystal structure) was regenerated as nanosized cellulose II particles with increased surface area and decreased crystallinity, determined by FE-SEM and XRD.

Laser photolysis studies of quaternary ammonium ionic liquids aqueous solution

The reactions between quaternary ammonium ionic liquids ((Me3NC2 H4OH) ? (Zn2Cl5) - , abbrev. Ch-Zn2Cl5) and one-electron oxidant (SO4- ), have been studied by nano-second laser photolysis techniques. The mechanism of monopho- tonic ionization by 266 nm laser excitation was suggested and the quantum yield was estimated to be 0.04. The second-order decay rate constant of SO4- oxidation reactions at 460 nm, 1.3 9 10 9 M -1 s -1 , was almost equal to the product rate constant of 1.5 9 10 9 M -1 s -1 at 320 nm in Ch-Zn2Cl5 aqueous solution showing that the decay and the product were synchronic. Comparison of Ch-Zn2Cl5 with chloride choline and ZnCl2 showed that the anion Zn2Cl5 - played an important role in photoionization while choline cation had little function on its photolysis and radiolysis. The present study would be helpful for understanding the application of ionic liquids in the field of electrochemical deposition.

Quaternary Ammonium Ionic Liquids as Bi-functional Catalysts for One-step Synthesis of Dimethyl Carbonate from Ethylene Oxide, Carbon Dioxide and Methanol

One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, 1H and 13C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bi-functional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results. One kind of novel quaternary ammonium ionic liquids has been developed and for the first time used as bi-functional catalysts in the one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide, CO2 and methanol. Normally, stronger basicity could be obtained by altering anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly.

Chiral quaternary alkylammonium ionic liquid [Pro-dabco][BF 4]: as a recyclable and highly efficient organocatalyst for asymmetric Michael addition reactions

A novel series of chiral quaternary ammonium ionic liquids have been synthesized and shown to be very effective catalysts for the asymmetric Michael addition reactions of ketones and aldehydes to nitroolefins with excellent yields (up to 100%), diastereoselectivities ( syn/ anti = 99:1), and enantioselectivities (up to 97%). The catalytic system, an ionic liquid organocatalyst in [Bmim][BF 4], could be reused five times without a significant loss in catalytic activity or stereoselectivity.

Lowering Melting Point and Viscosity Aliphatic Quaternary Ammonium Ionic Liquids by Modification of Perfluoroanions

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Film-Forming Properties of Propylene Carbonate in the Presence of a Quaternary Ammonium Ionic Liquid on Natural Graphite Anode

Propylene carbonate (PC) in electrolytes is generally believed to lead to graphite exfoliation due to intensive cointercalation and ceaseless decomposition reactions. This paper reports the formation of an effective solid electrolyte interface (SEI) film on a natural graphite surface through decomposition of PC in the presence of a quaternary ammonium ionic liquid. With an ionic liquid content of at least 60%, the PC molecules are reduced in the first charge, effectively passivating the graphite anode and allowing the formation of LiC6 with high capacity and good reversibility. In the electrolyte containing 20 vol % PC, the natural graphite anode attains a discharge capacity of 322.8 mAh/g and 76.5% coulombic efficiency on the first cycle. A stable discharge capacity of around 330 mAh/g was obtained in the initial 20 cycles without any noticeable capacity loss. This result compares favorably with using 20 vol % ethylene carbonate (EC) as the film-forming additive in the electrolyte. SEM and FTIR studies demonstrate the formation of a thin, homogeneous SEI layer on the graphite-electrode surface through the reduction of PC molecules. Raman spectroscopy studies show a significant decrease of the interaction between the Li ion and PC molecules in the presence of the quaternary ammonium ionic liquid. The competition for Li ions between PC and the ionic liquid reduces the solvation of PC molecules for Li ions, which in turn limits the intercalation of PC into the graphene layers during Li intercalation, an event that typically leads to exfoliation. Instead, the loosely bound PC is reduced at the graphite/electrolyte interface, forming a stable SEI.

Phosphonium and Ammonium Ionic Liquids with Aromatic Anions: Synthesis, Properties, and Platinum Extraction

Several hydrophobic long-chain quaternary ammonium and phosphonium ionic liquids (ILs) with functionalized aromatic anions were prepared following a metathesis route using tricaprylmethylammonium chloride (Aliquat 336) and trihexyl(tetradecyl)phosphonium chloride (Cyphos IL101) as precursors. The incorporation of aromatic anions bearing hydroxy-, methoxy-, thiol-, and thioether functionalities as well as tetraphenylborate anions resulted in an increased chemical stability of the ILs and an alteration of their physico-chemical properties. Furthermore, aromatic anions significantly decreased the water solubility and water uptake of both ammonium and phosphonium-based ILs. Thiol- and thioether ILs were applied for the extraction of platinum from aqueous phase using liquid phase micro-extraction. Time dependent studies showed a rapid elimination of up to 95% platinum after 30 min. With a leaching of the anion <0.01 wt-% into the aqueous media, the evaluated ILs were found to be suitable as extracting agents for platinum from aqueous solutions.

Multifunctional long-alkyl-chain quaternary ammonium azolate based ionic liquids

A new group of quaternary ammonium ionic liquids with azolate (benzotriazolate, 1,2,4-triazolate, 4-nitroimidazolate, 2-methyl-4-nitroimidazolate) anions was prepared and characterized. The synthetic method employed was easy and quick, and required a polar solvent. The obtained ionic liquids were tested as anti-microbial and anti-fungal plant protection agents. Additionally, the surface-active properties and the phytotoxicity of the quaternary ammonium azolates were also studied. These clearly defined ionic liquids were found to be very effective anti-bacterial and anti-fungal agents.

Removal of Cr(III, VI) by quaternary ammonium and quaternary phosphonium ionic liquids functionalized silica materials

Abstract A series of silica-based organic–inorganic hybrid materials were prepared by the sol–gel process for Cr(III) and Cr(VI) adsorption. These silica materials generally had high surface areas, good physical–chemical stability and high thermal stability. Trialkylmethylammonium bis 2,4,4-trimethylpentylphosphinate ([A336][C272]) and trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) were explored as porogens to prepare porous silica and as extractants to extract chromium ions. Cyphos IL 104 and [A336][C272] functionalized silica sorbents (SG-2, SG-5) can be effectively used for the removal of Cr(III) and Cr(VI) from aqueous solutions by adjusting pH values, whereas trialkylmethylammonium chloride (Aliquat 336) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) functionalized silica sorbents (SG-3, SG-4) can only be used for the removal of the single chromium species, Cr(VI) or Cr(III). The maximum adsorption amounts of Cr(III) and Cr(VI) were 2.14 and 19.31 mg g−1 for SG-2 and 2.32 and 15.29 mg g−1 for SG-5. Langmuir and Freundlich isotherm models were used to evaluate the adsorption of Cr(III) and Cr(VI) on sol–gel sorbents. The adsorption kinetics of Cr(III) and Cr(VI) on SG-2 and SG-5 could be well described by pseudo-second-order kinetic model. In terms of Cr(III) and Cr(VI) uptake capacities and kinetics, SG-2 and SG-5 appeared to be more suitable for Cr(III) and Cr(VI) removal than SG-3 and SG-4.

Lanthanide Bis[(trifluoromethyl)sulfonyl]imides as Reusable Catalysts for Mononitration of Substituted Benzenes in Ionic Liquids

AbstractLanthanide bis[(trifluoromethyl)sulfonyl]imides as a kind of effective catalyst were used in quaternary ammonium ionic liquids to afford a useful new method for the nitration of substituted benzenes with concentrated nitric acid (95%) as nitrating agent. The less expensive lanthanum bis[(trifluoromethyl)sulfonyl]imide was found to be the most effective catalyst employed in the ionic liquid tributylammonium bis[(trifluoromethyl)sulfonyl]imide. The lanthanum bis[(trifluoromethyl)sulfonyl]imide/tributylammonium bis[(trifluoromethyl)sulfonyl]imide system demonstrated high catalytic activity for the nitration of halobenzenes and rendered good to excellent yields. This catalyst/ionic liquid system could be recovered by simple procedures and recycled for at least 5 times.

Pd(II) catalyzed copolymerization of styrene and CO in quaternary ammonium ionic liquids

Poly(1-oxo-2-phenyltrimethylene) was synthesized by palladium-catalyzed copolymerization of styrene and carbon monoxide in quaternary ammonium ionic liquids. The [Pd(bipy)2][PF6]2 compound had relatively more catalytic activity than [Pd(bipy)2][BF4]2 in ionic liquids. The catalytic activity of palladium (II) composite catalyst was superior to the catalyst formedin situ from palladium acetate, 2,2-bipyridyl, and X− (X−=PF6 −, BF4 −) in ionic liquids. The effects of the volume of ionic liquids, reaction time and benzoquinone content on the copolymerization were also described.

Alkoxy Chain Effect on the Viscosity of a Quaternary Ammonium Ionic Liquid: Molecular Dynamics Simulations

The viscosity of ionic liquids based on quaternary ammonium cations is reduced when one of the alkyl chains is replaced by an alkoxy chain ( Zhou et al. Chem. Eur. J. 2005 , 11 , 752. ). A microscopic picture of the role played by the ether function in decreasing the viscosity of quaternary ammonium ionic liquids is provided here by molecular dynamics (MD) simulations. A model for the ionic liquid N-ethyl-N,N-dimethyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, MOENM(2)E TFSI, is compared to the tetraalkylammonium counterpart. The alkoxy derivative has lower viscosity, higher ionic diffusion coefficients, and higher conductivity than the tetraalkyl system at the same density and temperature. A clear signature of the ether function on the liquid structure is observed in cation-cation correlations, but not in anion-anion or anion-cation correlations. In both the alkyl and the alkoxy ionic liquids, there is aggregation of long chains of neighboring cations within micelle-like structures. The MD simulations indicate that the less effective assembly between the more flexible alkoxy chains, in comparison to alkyl chains, is the structural reason for higher ionic mobility in MOENM(2)E TFSI.

Ordering Structure of Binary Aliphatic Quaternary Ammonium Ionic Liquids: AQA-TFSA Systems

The effects of secondary cationic species on the ordering structure in room temperature ionic liquids (RTILs) are discussed. Binary RTILs refer to mixture of trimetyl-n-octylammonium bis(trifluoromethanesulfonyl)imide (N1118[TFSA]) and alkali or alkali-earth metal bis(trifluoromethanesulfonyl)imide (M[TFSA]y; M=Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba) in an appropriate molar ratio (x=0.1, 0.2, 0.3, 0.5), denoted as Mx[N1118]1−x[TFSA]1−x+xy. From SAXS and WAXS measurements of Mx[N1118]1−x[TFSA]1−x+xy, the intensity of first peak derived from the ordering structure increases with addition of M[TFSA]y. It is suggested that the metal cation has an intensive interaction with TFSA anion and cationic structural ordering are enhanced. We discussed the relationship between ionic size and the formation mechanism of the local ordering structure in binary ionic liquids containing alkali metal and alkali earth metal based on aliphatic quaternary ammonium (AQA) cations is clarified.

Nitration of Substituted Benzenes Catalyzed by Metal Bis[(perfluoroalkyl)sulfonyl]imides in Quaternary Ammonium Ionic Liquids

AbstractThe nitrations of substituted benzenes proceeded rapidly and cleanly with very good yields in Cu(N(C4F9SO2)2)2/ [N4446][Tf2N] or In(NTf2)3/[N4446][Tf2N] catalyst system, in which HNO3/Ac2O was used as the nitrating agent. For the nitration of chlorobenzene when 2 mol% catalyst was used at room temperature for 10 min, 87.6% and 90.6% of conversion of chlorobenzene were achieved, respectively and the para/ortho ratios of products were about 4.3–4.8. The catalyst systems with ionic liquid could be recovered easily and reused more than 5 times.

Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration

Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.

Phase Equilibria and Modeling of Ammonium Ionic Liquid, C2NTf2, Solutions

Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated.

Dye-Sensitized Solar Cells Based on Quaternary Phosphonium Ionic Liquids as Electrolytes

Abstract Dye-sensitized solar cells using quaternary phosphonium ionic liquids as their electrolytes have been successfully fabricated. Of these, the best device performance was achieved by using triethyl(pentyl)phosphonium bis(trifluoromethylsulfonyl)amide, whose energy conversion efficiencies were determined to be 1.2% and 3.8% under full (AM 1.5, 100 mW cm−2) and low intensity (7 mW cm−2) sunlight illumination, respectively. Interestingly, the energy conversion efficiencies for the quaternary phosphonium ionic liquid electrolytes are higher than those for the corresponding quaternary ammonium ionic liquids.

Liquid Phase Behavior of Ionic Liquids with Water and 1-Octanol and Modeling of 1-Octanol/Water Partition Coefficients

This study examines the effect of structural components of an ionic liquid (IL), including the choice of the anion, alkyl chain length on the cation, and substitution on the cation, on the mutual solubility with water and with 1-octanol. This is important because ionic liquids have been shown to be good replacements for organic extraction solvents in some liquid separations. In addition, we use the measured data to predict 1-octanol/water partition coefficients for the ionic liquids using the nonrandom two liquid (NRTL) and electrolyte nonrandom two liquid (eNRTL) excess Gibbs energy models. Specifically, the mutual solubilities of 15 different imidazolium, pyridinium, and quaternary ammonium ionic liquids with water were measured at (23.5 ± 1) °C. An increase in the alkyl chain length or the substitution decreases the mutual solubility with water. The [BF4]- and [B(CN)4]- anions are significantly more hydrophilic than [PF6]-, [(CF3SO2)2N]-, and [(CF3SO2)3C]-. The mutual solubilities of 10 ILs with 1-octa...

Investigation of Ether-Substituted Quaternary Ammonium Ionic Liquids

The effect of structural rigidity in quaternary ammonium-based ionic liquids (ILs) was investigated. and , both 8 atom (7 carbons, 1 oxygen) ether-substituted quaternary ammonium chlorides (Quats), were syn thesized and investigated. In acetonitrile, placement of the oxygen one atom from the nitrogen (Quat I) resulted in a significant decrease in the reductive stability. While the IL form showed similar stability for the two systems, placing the oxygen close to the nitrogen (methyl ethyl ether) appears to localize a greater portion of the positive charge on the nitrogen. This results in an IL with a higher melting point than the nonether analog, (III, ) IL. In contrast, placing two carbon atoms between the nitrogen and ether group, ethyl methyl ether (Quat II), delocalizes the positive charge from the nitrogen and produces a room-temperature IL. Neutralization of the acidic IL with sodium chloride resulted in an increase in the bulk conductivity, due to the polar ether group. Upon addition of or , which both form a solid-electrolyte interphase on the substrate surface, the increased free sodium ion concentration allowed sodium reduction and oxidation currents greater than at room temperature.

Efficient catalytic synthesis of optically active cyclic carbonates via coupling reaction of epoxides and carbon dioxide

Chiral Co(salen) complexes bearing the Lewis acid of group 13 can efficiently catalyze the reactions of carbon dioxide with epoxides in the presence of catalytic amounts of alkali metal salts, quaternary ammonium halide or ionic liquids. They exhibited excellent activity for producing enantiomerically enriched cyclic carbonates.