Showing papers on "Ionic liquid published in 2005"
TL;DR: The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.
Abstract: Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.
2,790 citations
TL;DR: The alkyl chain length of 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide was varied to prepare a series of room-temperature ionic liquids (RTILs), and the thermal behavior, density, viscosity, self-diffusion coefficients, and ionic conductivity were measured over a wide temperature range.
Abstract: The alkyl chain length of 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide ([Rmim][(CF3SO2)2N], R = methyl (m), ethyl (e), butyl (b), hexyl (C6), and octyl (C8)) was varied to prepare a series of room-temperature ionic liquids (RTILs), and the thermal behavior, density, viscosity, self-diffusion coefficients of the cation and anion, and ionic conductivity were measured over a wide temperature range. The self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity change with temperature following the Vogel−Fulcher−Tamman equation, and the density shows a linear decrease. The pulsed-field-gradient spin−echo NMR method reveals a higher self-diffusion coefficient for the cation compared to that for the anion over a wide temperature range, even if the cationic radius is larger than that of the anion. The summation of the cationic and anionic diffusion coefficients for the RTILs follows the order [emim][(CF3SO2)2N] > [mmim][(CF3SO2)2N] > [bmim][(CF3SO2)2N] > [C6mim][(CF3SO2)...
1,549 citations
TL;DR: Amino acid ionic liquids dissolved native amino acids, despite water-free conditions, and are soluble in various organic solvents, such as chloroform.
Abstract: We first succeeded in synthesizing ionic liquids from 20 natural amino acids. Amino acid ionic liquids dissolved native amino acids, despite water-free conditions. Furthermore, these ionic liquids are soluble in various organic solvents, such as chloroform. Effects of acidity, hydrogen bonding ability, and steric factors on the properties of these ionic liquids were analyzed as the function of side groups.
1,101 citations
1,066 citations
TL;DR: Ionic liquids are a fascinating class of novel solvents, which are attracting attention as a possible green alternative to volatile molecular organic solutions to be applied in catalytic and organic reactions and electrochemical and separation processes as mentioned in this paper.
1,051 citations
TL;DR: Ionic liquids with the bis(trifluoromethylsulfonyl) imide anion had the largest affinity for CO(2), regardless of whether the cation was imidazolium, pyrrolidinium, or tetraalkylammonium.
Abstract: This work presents the results of solubility measurements for a series of gases in 1-n-butyl-3-methyl imidazolium tetrafluoroborate and 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide. The gases considered include benzene, carbon dioxide, nitrous oxide, ethylene, ethane, oxygen, and carbon monoxide. Carbon dioxide and oxygen solubilities are also reported in methyl-tributylammonium bis(trifluoromethylsulfonyl) imide, butyl-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide, and tri-isobutyl-methyl phosphonium p-toluenesulfonate. We report the associated Henry's constants and enthalpies and entropies of absorption. In general, benzene, followed by carbon dioxide and nitrous oxide, have the highest solubilities and strongest interactions with the ionic liquids, followed by ethylene and ethane. Oxygen had very low solubilities and weak interactions. Carbon monoxide had a solubility below the detection limit of our apparatus. Ionic liquids with the bis(trifluoromethylsulfonyl) imide ani...
925 citations
TL;DR: A multiscale coarse-graining model for ionic liquids has been extended and it has been found that, with sufficiently long side chains, the tail groups of cations aggregate to form spatially heterogeneous domains, while headgroups of the cations and the anions distribute as uniformly as possible.
Abstract: A multiscale coarse-graining model for ionic liquids has been extended to investigate the unique aggregation of cations in ionic liquids through computer simulation. It has been found that, with sufficiently long side chains, the tail groups of cations aggregate to form spatially heterogeneous domains, while headgroups of the cations and the anions distribute as uniformly as possible. This is understood as the result of competition between the charged electrostatic interactions between headgroups and anions and the collective short-range interactions between the neutral tail groups. This aggregation can help to explain a number of experimentally observed physical phenomena in ionic liquids.
898 citations
TL;DR: Polymer gels obtained by the polymerization of methyl methacrylate (MMA) in EMITFSI in the presence of a small amount of a cross-linker gave self-standing, flexible, and transparent films.
Abstract: To realize polymer electrolytes with high ionic conductivity, we exploited the high ionic conductivity of an ionic liquid. In situ free radical polymerization of compatible vinyl monomers in a room temperature ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethane sulfonyl)imide (EMITFSI), afforded a novel series of polymer electrolytes. Polymer gels obtained by the polymerization of methyl methacrylate (MMA) in EMITFSI in the presence of a small amount of a cross-linker gave self-standing, flexible, and transparent films. The glass transition temperatures of the gels, which we named "ion gels", decreased with increasing mole fraction of EMITFSI and behaved as a completely compatible binary system of poly(methyl methacrylate) (PMMA) and EMITFSI. The temperature dependence of the ionic conductivity of the ion gels followed the Vogel-Tamman-Fulcher (VTF) equation, and the ionic conductivity at ambient temperature reached a value close to 10(-2) S cm(-1). Similarly to the behavior of the ionic liquid, the cation in the ion gels diffused faster than the anion. The number of carrier ions, calculated from the Nernst-Einstein equation, was found to increase for an ion gel from the corresponding value for the ionic liquid itself. The cation transference number increased with decreasing EMITFSI concentration due to interaction between the PMMA matrix and the TFSI(-) anion, which prohibited the formation of ion clusters or associates, as was the case for the ionic liquid itself.
866 citations
TL;DR: A switchable solvents system that converts to an ionic liquid upon exposure to an atmosphere of carbon dioxide, and then reverts back to its non-ionic form when exposed to nitrogen or argon gas is created.
Abstract: Imagine a smart solvent that can be switched reversibly from a liquid with one set of properties to another that has very different properties, upon command. Here we create such a system, in which a non-ionic liquid (an alcohol and an amine base) converts to an ionic liquid (a salt in liquid form) upon exposure to an atmosphere of carbon dioxide, and then reverts back to its non-ionic form when exposed to nitrogen or argon gas. Such switchable solvents should facilitate organic syntheses and separations by eliminating the need to remove and replace solvents after each reaction step.
821 citations
TL;DR: In this article, a review summarizes recent applications of ionic liquids (ILs) as green solvents in extractions of a variety of substances, including metal ions, organic and bio-molecules, organosulfur from fuels, and gases.
Abstract: This review summarizes recent applications of ionic liquids (ILs) as ‘green’ solvents in extractions of a variety of substances, including metal ions, organic and bio-molecules, organosulfur from fuels, and gases. ILs could also be used along with another ‘green’ technology, supercritical fluid extraction (SFE), for a more effective separation of products from ILs. In addition to their environmentally-benign feature, ILs have other favorable properties over organic solvents used for extraction, such as adjustable hydrophobicity, polarity and selectivity. Copyright © 2005 Society of Chemical Industry
13 Apr 2005
TL;DR: Thirty-nine geminal dicationic ILs were synthesized and characterized in terms of their surface tensions, densities, melting points, refractive indices, viscosities, and miscibilities with a polar and nonpolar solvent.
Abstract: Thirty-nine geminal dicationic ILs were synthesized and characterized in terms of their surface tensions, densities, melting points, refractive indices, viscosities, and miscibilities with a polar and nonpolar solvent. Two imidazolium or pyrrolidinium cations were joined via different length hydrocarbon linkage chains (from 3 to 12 carbons long). The various geminal dications were paired with up to four different anions. The effect of the dication type, linkage chain, alkyl substituents, and anion type on the physicochemical properties of these compounds was examined. Among the more interesting findings for this class of compounds was that their liquid and thermal stability ranges generally exceeded those of the more conventional, better known ILs. Indeed, this range was from -4 to >400 degrees C for one of the pyrrolidinium-based geminal dicationic liquids. X-ray crystallography of the smaller solid ionic compounds indicated that there may be a correlation between the configurational degrees of freedom of the ILs and their melting points/glass transition temperatures. In one case, the crystal structure showed that a dicationic moiety had three distinct conformations in an asymmetric unit cell. The solvation properties of the geminal dicationic ILs tend to be similar to those of their monocationic analogues.
TL;DR: In this article, the authors present melting temperatures, glass transition temperatures, decomposition temperatures, heat capacities, and viscosities for a large series of pyridinium-based ionic liquids.
TL;DR: The synthesis of ionic liquids and their applications in various chemical and biochemical transformations, in ecofriendly-milder conditions have been reviewed in this paper, with metal and enzyme catalyzed as well as non-catalyzed reactions in ionic liquid reactions covered with 354 refs.
TL;DR: In this paper, a review of the efforts to determine empirically the polarity of room-temperature ionic liquids by means of the zwitterionic betaine dye 2,6-diphenyl-4-(2,4-6-triphenylpyridinium-1-yl)phenolate is summarized and discussed.
TL;DR: The solvent properties of ionic liquids, their effects on enzyme performance such as activity, stability and selectivity, and their applications in biocatalysis are discussed.
TL;DR: It was confirmed that this IL is a so-called non-derivatizing solvent, which can be applied as a reaction medium for the synthesis of carboxymethyl cellulose and cellulose acetate and without using any catalyst, cellulose derivatives with high degree of substitution could be prepared.
Abstract: The application of different ionic liquids (IL), namely 1-N-butyl-3-methylimidazolium chloride ([C(4)mim](+)Cl(-)), 3-methyl-N-butyl-pyridinium chloride and benzyldimethyl(tetradecyl)ammonium chloride were investigated as solvents for cellulose. The ILs used have the ability to dissolve cellulose with a degree of polymerization in the range from 290 to 1 200 to a very high concentration. Using [C(4)mim](+)Cl(-), no degradation of the polymer appears. By (13)C NMR measurement it was confirmed that this IL is a so-called non-derivatizing solvent. [C(4)mim](+)Cl(-) can be applied as a reaction medium for the synthesis of carboxymethyl cellulose and cellulose acetate. Without using any catalyst, cellulose derivatives with high degree of substitution could be prepared.(13)C NMR spectrum of cellulose dissolved in the IL [C(4)mim](+)Cl(-) (top). The (13)C NMR spectrum of cellulose dissolved in DMSO/tetrabutylammonium fluoride trihydrate is shown for comparison (bottom).
TL;DR: This research has identified the first ILs which can be classified as ‘readily biodegradable’ under aerobic conditions.
TL;DR: The experimental solubility data of CO2 in ionic liquids have been successfully correlated for the first time using a simple cubic equation of state (EOS) model as discussed by the authors.
Abstract: Gaseous carbon dioxide (CO2) absorption measurements in l-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and l-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) were made using a commercial gravimetric microbalance at temperatures of 283.15, 298.15, 323.15, and 348.15 K and at pressures under 2 MPa. Gas solubilities were determined from absorption saturation (equilibrium) data at each fixed temperature and pressure. The experimental solubility data of CO2 in ionic liquids have been successfully correlated for the first time using a simple cubic equation of state (EOS). Some phase behaviors of CO2 and ionic liquid mixtures as well as Henry's law constants and the volume change of solutions are predicted well with the present EOS model. From time-dependent absorption data, binary diffusion coefficients of CO2 in the ionic liquids have been obtained for the first time by the use of a simple diffusion model. Magnitudes in the observed diffusion coefficients are 10-10 to 10-11 m2 s-1, ...
TL;DR: A brief overview of the application of ionic liquids in analytical chemistry can be found in this article, including sample preparation, chromatographic/capillary electrophoretic (CE) separation, and detection.
Abstract: Room-temperature ionic liquids (ILs) are gaining wide recognition as novel solvents in chemistry. Their application in analytical chemistry, especially in separating analytes, is merited because ILs have some unique properties, such as negligible vapor pressure, good thermal stability, tunable viscosity and miscibility with water and organic solvents, as well as good extractability for various organic compounds and metal ions. This review gives a brief overview of the application of ILs in analytical chemistry, including sample preparation, chromatographic/capillary electrophoretic (CE) separation, and detection. (C) 2004 Elsevier Ltd. All rights reserved.
TL;DR: Recent advances made in supported ionic liquid catalysis are described.
Abstract: Supported ionic liquid catalysis is a concept which combines the advantages of ionic liquids with those of heterogeneous support materials. The viability of this concept has been confirmed by several studies which have successfully confined various ionic phases to the surface of support materials and explored their potential catalytic applications. Although the majority of the evaluated supports were silica based, several studies focused on polymeric materials including membranes. The preparation of these materials was achieved by using two different immobilization approaches. The first approach involves the covalent attachment of ionic liquids to the support surface whereas the second simply deposits the ionic liquid phases containing catalytically active species on the surface of the support. Herein recent advances made in this area are described.
TL;DR: In this paper, three ionic liquids were chosen for study based on their range of solvent properties and the solvent properties correlate with solubility of water in the ionic liquid.
TL;DR: The results indicate markedly lower polarities than found by spectroscopy with polarity-sensitive solvatochromic dyes, and the salts are classified as moderately polar solvents.
Abstract: In a pilot study of the dielectric constant of room-temperature ionic liquids, we use dielectric spectroscopy in the megahertz/gigahertz regime to determine the complex dielectric function of five 1-alkyl-3-methylimidazolium salts, from which the static dielectric constant e is obtained by zero-frequency extrapolation. The results classify the salts as moderately polar solvents. The observed e-values at 298.15 K fall between 15.2 and 8.8, and e decreases with increasing chain length of the alkyl residue of the cation. The anion sequence is trifluoromethylsulfonate > tetrafluoroborate ≈ tetrafluorophosphate. The results indicate markedly lower polarities than found by spectroscopy with polarity-sensitive solvatochromic dyes.
TL;DR: A family of biocompatible ionic liquids which are able to dissolve significant amounts of proteins such as cytochrome c and in which ATR-FTIR spectroscopy results show retention of secondary structure to extreme temperatures are reported.
TL;DR: Comparison with the experimental ionic conductivities shows that the magnitude and directionality of the interaction energy of the ion pairs play a crucial role in determining the ionic dissociation/association dynamics in the ionsic liquids.
Abstract: The intermolecular interaction energies of nine ion pairs of room temperature ionic liquids were studied by MP2/6-311G** level ab initio calculations. The magnitude of the interaction energies of 1-ethyl-3-methylimidazolium (emim) complexes follows the trend CF3CO2- > BF4- > CF3SO3- > (CF3SO2)2N- ∼ PF6- (−89.8, −85.2, −82.6, −78.8, and −78.4 kcal/mol, respectively). The interaction energies of BF4- complexes with emim, ethylpyridinium (epy), N-ethyl-N,N,N-trimethylammonium ((C2H5)(CH3)3N), and N-ethyl-N-methylpyrrolidinium (empro) are not very different (−85.2, −82.8, −84.6, and −84.4 kcal/mol, respectively), while the size of the orientation dependence of the interaction energies follows the trend emim > epy ∼ (C2H5)(CH3)3N > empro. Comparison with the experimental ionic conductivities shows that the magnitude and directionality of the interaction energy of the ion pairs play a crucial role in determining the ionic dissociation/association dynamics in the ionic liquids. The electrostatic interaction is t...
TL;DR: A task-specific ionic liquid, [bmIm]OH, has been introduced as a catalyst and as a reaction medium in Michael addition, which drives the reaction of open-chain 1,3-dicarbonyl compounds with alpha,beta-unsaturated esters and nitriles toward bis-addition to produce exclusively bis-adducts in one stroke.
TL;DR: In this article, Li-air batteries using hydrophobic ionic liquid consisting of 1-alkyl-3-methyl imidazolium cation and perfluoroalkylsulfonyl imide anion were investigated.
TL;DR: Recent progress made in the application of ionic liquids toward analytical problem-solving is chronicles and results to date commend their use in various modes of chemical analysis.
Abstract: Within the last decade, ionic liquids have come to the fore as environmentally-responsible designer solvents. But what are ionic liquids and what can they offer the analytical scientist? This article addresses these questions and chronicles recent progress made in the application of ionic liquids toward analytical problem-solving. While further progress is required before ionic liquids become mainstream analytical solvents, results to date commend their use in various modes of chemical analysis. It is our aim that the findings reported herein draw other researchers into this area and encourage the increased application of ionic liquids in this manner.