Showing papers on "Ionic liquid published in 2006"
TL;DR: In this paper, the physical and chemical properties of room temperature ionic liquids (RTILs) are reviewed from the point of view of their possible application as electrolytes in electrochemical processes and devices.
2,241 citations
TL;DR: It is demonstrated that some selected families of commonly used aprotic ionic liquids can be distilled at 200–300 °C and low pressure, with concomitant recovery of significant amounts of pure substance, will permit these currently excluded applications to be realized.
Abstract: It is widely believed that a defining characteristic of ionic liquids (or low-temperature molten salts) is that they exert no measurable vapour pressure, and hence cannot be distilled. Here we demonstrate that this is unfounded, and that many ionic liquids can be distilled at low pressure without decomposition. Ionic liquids represent matter solely composed of ions, and so are perceived as non-volatile substances. During the last decade, interest in the field of ionic liquids has burgeoned, producing a wealth of intellectual and technological challenges and opportunities for the production of new chemical and extractive processes, fuel cells and batteries, and new composite materials. Much of this potential is underpinned by their presumed involatility. This characteristic, however, can severely restrict the attainability of high purity levels for ionic liquids (when they contain poorly volatile components) in recycling schemes, as well as excluding their use in gas-phase processes. We anticipate that our demonstration that some selected families of commonly used aprotic ionic liquids can be distilled at 200-300 degrees C and low pressure, with concomitant recovery of significant amounts of pure substance, will permit these currently excluded applications to be realized.
1,900 citations
TL;DR: As the length of the alkyl chain increases, the nonpolar domains become larger and more connected and cause swelling of the ionic network, in a manner analogous to systems exhibiting microphase separation.
Abstract: Nanometer-scale structuring in room-temperature ionic liquids is observed using molecular simulation. The ionic liquids studied belong to the 1-alkyl-3-methylimidazolium family with hexafluorophosphate or with bis(trifluoromethanesulfonyl)amide as the anions, [Cnmim][PF6] or [Cnmim][(CF3SO2)2N], respectively. They were represented, for the first time in a simulation study focusing on long-range structures, by an all-atom force field of the AMBER/OPLS_AA family containing parameters developed specifically for these compounds. For ionic liquids with alkyl side chains longer than or equal to C4, aggregation of the alkyl chains in nonpolar domains is observed. These domains permeate a tridimensional network of ionic channels formed by anions and by the imidazolium rings of the cations. The nanostructures can be visualized in a conspicuous way simply by color coding the two types of domains (in this work, we chose red = polar and green = nonpolar). As the length of the alkyl chain increases, the nonpolar domai...
1,668 citations
TL;DR: In this article, the dissolution of cellulose with ionic liquids and its application were reviewed, where cellulose can be easily regenerated from its ionic liquid solutions by addition of water, ethanol or acetone.
1,488 citations
TL;DR: In this article, a comprehensive database on physical properties of ionic liquids (ILs), collected from 109 kinds of literature sources in the period from 1984 through 2004, has been presented, which includes 1680 pieces of data on the physical properties for 588 available ILs, from which 276 kinds of cations and 55 kinds of anions were extracted.
Abstract: A comprehensive database on physical properties of ionic liquids (ILs), which was collected from 109 kinds of literature sources in the period from 1984 through 2004, has been presented. There are 1680 pieces of data on the physical properties for 588 available ILs, from which 276 kinds of cations and 55 kinds of anions were extracted. In terms of the collected database, the structure-property relationship was evaluated. The correlation of melting points of two most common systems, disubstituted imidazolium tetrafluoroborate and disubstituted imidazolium hexafluorophosphate, was carried out using a quantitative structure-property relationship method.
1,102 citations
TL;DR: The Lambda(imp)/Lambda(NMR) well illustrates the degree of cation-anion aggregation in the RTILs at equilibrium, which can be explained by the effects of anionic donor and cationic acceptor abilities for the RTils having different anionic andcationic backbone structures with fixed counterparts, and by the inductive and dispersive forces for the various alkyl chain lengths in the cations.
Abstract: Room-temperature ionic liquids (RTILs) are liquids consisting entirely of ions, and their important properties, e.g., negligible vapor pressure, are considered to result from the ionic nature. However, we do not know how ionic the RTILs are. The ionic nature of the RTILs is defined in this study as the molar conductivity ratio (Λimp/ΛNMR), calculated from the molar conductivity measured by the electrochemical impedance method (Λimp) and that estimated by use of pulse-field-gradient spin−echo NMR ionic self-diffusion coefficients and the Nernst−Einstein relation (ΛNMR). This ratio is compared with solvatochromic polarity scales: anionic donor ability (Lewis basicity), ET(30), hydrogen bond donor acidity (α), and dipolarity/polarizability (π*), as well as NMR chemical shifts. The Λimp/ΛNMR well illustrates the degree of cation−anion aggregation in the RTILs at equilibrium, which can be explained by the effects of anionic donor and cationic acceptor abilities for the RTILs having different anionic and catio...
1,074 citations
TL;DR: It is reported that polarsolvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2), facilitating an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu( 0) atomic species.
Abstract: Conventional metal-catalyzed organic radical reactions and living radical polymerizations (LRP) performed in nonpolar solvents, including atom-transfer radical polymerization (ATRP), proceed by an inner-sphere electron-transfer mechanism. One catalytic system frequently used in these polymerizations is based on Cu(I)X species and N-containing ligands. Here, it is reported that polar solvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2) species in the presence of a diversity of N-containing ligands. This disproportionation facilitates an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu(0) atomic species, while their deactivation is mediated by the nascent Cu(II)X(2) species. Both steps proceed by a low activation energy outer-sphere single-electron-transfer (SET) mechanism. The resulting SET-LRP process is activated by a catalytic amount of the electron-donor Cu(0), Cu(2)Se, Cu(2)Te, Cu(2)S, or Cu(2)O species, not by Cu(I)X. This process provides, at room temperature and below, an ultrafast synthesis of ultrahigh molecular weight polymers from functional monomers containing electron-withdrawing groups such as acrylates, methacrylates, and vinyl chloride, initiated with alkyl halides, sulfonyl halides, and N-halides.
1,058 citations
TL;DR: In this review article, a short overview on physicochemical aspects of ionic liquids, such as physical properties of ions, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ions are given.
Abstract: Ionic liquids are defined today as liquids which solely consist of cations and anions and which by definition must have a melting point of 100 °C or below. Originating from electrochemistry in AlCl3 based liquids an enormous progress was made during the recent 10 years to synthesize ionic liquids that can be handled under ambient conditions, and today about 300 ionic liquids are already commercially available. Whereas the main interest is still focussed on organic and technical chemistry, various aspects of physical chemistry in ionic liquids are discussed now in literature. In this review article we give a short overview on physicochemical aspects of ionic liquids, such as physical properties of ionic liquids, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ionic liquids. The focus is set on air and water stable ionic liquids as they will presumably dominate various fields of chemistry in future.
1,052 citations
TL;DR: In this paper, the authors measured the viscosity and density of six ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, 1-Butyl 3methylammonium bis(trifluoromethylsulfonyl)imide, butyltrimethylammmonium, ethyl sulfate and butyl trifluoric acid) with an accuracy of 10−3 g cm−3 and 1%, respectively.
762 citations
TL;DR: The use of nitrogen containing anions and cations contributes to high heats of formations and high densities as discussed by the authors, which makes them very promising candidates for highly energetic materials for industrial or military applications.
Abstract: Energetic salts offer many advantages over conventional energetic molecular compounds. The use of nitrogen containing anions and cations contributes to high heats of formations and high densities. Their low carbon and hydrogen content gives rise to a good oxygen balance. The decomposition of these compounds is predominantly through the generation of dinitrogen which makes them very promising candidates for highly energetic materials for industrial or military applications.
709 citations
TL;DR: C and 35/37Cl NMR relaxation measurements on several model systems demonstrate that the solvation of cellulose by the ionic liquid 1-n-butyl-3-methylimidazolium chloride involves hydrogen-bonding between the carbohydrate hydroxyl protons and the IL chloride ions in a 1 ratio 1 stoichiometry.
TL;DR: Recent developments in task specifically functionalized imidazolium salts, which can be used for specific tasks ranging from catalysts recycling, supports for organic synthesis, catalysis, separation of specific metal ions from aqueous solution, and construction of nanostructures and ion conductive materials, have been reviewed.
TL;DR: NMR studies in conjunction with DFT/GIAO chemical shift calculations indicate that both polyaminoborane and the diammoniate of diborane, [(NH3)2BH2+]BH4-, are initial products in the reactions.
Abstract: Ionic liquids are shown to provide advantageous media for amineborane-based chemical hydrogen storage systems. Both the extent and rate of hydrogen release from ammonia borane dehydrogenation are significantly increased at 85, 90, and 95 degrees C when the reactions are carried out in 1-butyl-3-methylimidazolium chloride compared to analogous solid-state reactions. NMR studies in conjunction with DFT/GIAO chemical shift calculations indicate that both polyaminoborane and the diammoniate of diborane, [(NH3)2BH2+]BH4-, are initial products in the reactions.
TL;DR: An attempt was made to disrupt the cellulose structure using the ionic liquid, 1‐n‐butyl‐3‐methylimidazolium chloride, in a cellulose regeneration strategy which accelerated the subsequent hydrolysis reaction.
Abstract: Hydrolysis of cellulose to glucose in aqueous media catalyzed by the cellulase enzyme system suffers from slow reaction rates due in large part to the highly crystalline structure of cellulose and inaccessibility of enzyme adsorption sites. In this study, an attempt was made to disrupt the cellulose structure using the ionic liquid (IL), 1-n-butyl-3-methylimidazolium chloride, in a cellulose regeneration strategy which accelerated the subsequent hydrolysis reaction. ILs are a new class of non-volatilesolventsthatexhibituniquesolvatingproper- ties. They can be tuned to dissolve a wide variety of compounds including cellulose. Because of their extre- mely low volatility, ILs are expected to have minimal environmental impact on air quality compared to most other volatile solvent systems. The initial enzymatic hydrolysis rates were approximately 50-fold higher for regenerated cellulose as compared to untreated cellulose (Avicel PH-101) as measured by a soluble reducing sugar
TL;DR: A simple and quantitative explanation for the relatively low melting temperatures of ionic liquids (ILs) is developed, and from very little experimental and computational data it is possible to predict fundamental properties such as melting points and dielectric constants of Ionic liquids with good accuracy.
Abstract: We have developed a simple and quantitative explanation for the relatively low melting temperatures of ionic liquids (ILs). The basic concept was to assess the Gibbs free energy of fusion (ΔfusG) for the process IL(s) → IL(l), which relates to the melting point of the IL. This was done using a suitable Born−Fajans−Haber cycle that was closed by the lattice (i.e., IL(s) → IL(g)) Gibbs energy and the solvation (i.e., IL(g) → IL(l)) Gibbs energies of the constituent ions in the molten salt. As part of this project we synthesized and determined accurate melting points (by DSC) and dielectric constants (by dielectric spectroscopy) for 14 ionic liquids based on four common anions and nine common cations. Lattice free energies (ΔlattG) were estimated using a combination of Volume Based Thermodynamics (VBT) and quantum chemical calculations. Free energies of solvation (ΔsolvG) of each ion in the bulk molten salt were calculated using the COSMO solvation model and the experimental dielectric constants. Under stand...
TL;DR: The absence of decomposition of ILs during the vaporization process was proved by IR spectroscopy and Thermodynamic parameters of vaporization for ILs were calculated.
Abstract: Vapor pressures for a series of 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (alkyl = ethyl, butyl, hexyl, and octyl) ionic liquids (ILs) were measured by the integral effusion Knudsen method. Thermodynamic parameters of vaporization for ILs were calculated from these data. The absence of decomposition of ILs during the vaporization process was proved by IR spectroscopy. Enthalpies of vaporization of ILs were correlated with molar volumes and surface tensions of the compounds.
TL;DR: In this article, quantitative structure-property relationship models are developed to assess the factors that govern the toxicity of a range of different ionic liquids to two aquatic organisms (Vibrio fischeri and Daphnia magna).
01 Jan 2006
TL;DR: In this paper, an attempt was made to disrupt the cellulose structure using the ionic liquid (IL), 1−n−butyl−3−methylimidazolium chloride, in a cellulose regeneration strategy which accelerated the subsequent hydrolysis reaction.
Abstract: Hydrolysis of cellulose to glucose in aqueous media catalyzed by the cellulase enzyme system suffers from slow reaction rates due in large part to the highly crystalline structure of cellulose and inaccessibility of enzyme adsorption sites. In this study, an attempt was made to disrupt the cellulose structure using the ionic liquid (IL), 1‐n‐butyl‐3‐methylimidazolium chloride, in a cellulose regeneration strategy which accelerated the subsequent hydrolysis reaction. ILs are a new class of non‐volatile solvents that exhibit unique solvating properties. They can be tuned to dissolve a wide variety of compounds including cellulose. Because of their extremely low volatility, ILs are expected to have minimal environmental impact on air quality compared to most other volatile solvent systems. The initial enzymatic hydrolysis rates were approximately 50‐fold higher for regenerated cellulose as compared to untreated cellulose (Avicel PH‐101) as measured by a soluble reducing sugar assay. © 2006 Wiley Periodicals, Inc.
TL;DR: In this article, the solubility of 17 commonly available metal oxides in the elemental mass series Ti through Zn have been determined in three ionic liquids based on choline chloride.
Abstract: The solubility of 17 commonly available metal oxides in the elemental mass series Ti through Zn have been determined in three ionic liquids based on choline chloride. The hydrogen bond donors used were urea, malonic acid, and ethylene glycol. The results obtained are compared with aqueous solutions of HCl and NaCl. Some correlation is observed between the solubility in the deep eutectic solvents and that in aqueous solutions but some significant exceptions offer an opportunity for novel solvato-metallurgical processes.
TL;DR: In this paper, a charge-discharge cycling test of a Li/LiCoO 2 cell containing ionic liquids based on bis(fluorosulfonyl)imide ([FSI] − ) as the electrolyte media, revealed significantly better rate properties compared to those of cells using conventional ionic liquid.
TL;DR: This is the third set of parameters of a force field for the molecular simulation of ionic liquids, developed within the spirit of the OPLS-AA model and thus oriented toward the calculation of equilibrium thermodynamic and structural properties.
Abstract: This is the third set of parameters of a force field for the molecular simulation of ionic liquids, developed within the spirit of the OPLS-AA model and thus oriented toward the calculation of equilibrium thermodynamic and structural properties. The parameter sets reported here concern the cations alkylimidazolium, tetra-alkylphosphonium, and N-alkylpyridinium, and the anions chloride, bromide, and dicyanamide. The force field is built in a stepwise manner that allows the construction of models for an entire family of cations, with alkyl side chains of different length, for example. Due to the transferability of the present force field, the ions studied here can be combined with those reported in our two previous publications to create a large variety of ionic liquids that can be studied by molecular simulation. The parameters reported were obtained through different series of ab initio calculations concerning the geometry, force constants, torsion energy profiles, and electrostatic charge distributions of the ions under study. Validation of the force field consisted of comparison with experimental crystal structure and liquid density data.
TL;DR: Low viscosity, polar, and halogen-free ionic liquids are prepared as potential solvents for a wide range of polysaccharides including amylose and (scarcely soluble) cellulose under mild condition.
TL;DR: In this article, a graphite negative electrode with bis(fluorosulfonyl)imide (FSI) as an anion and 1-ethyl-3-methylimidazolium (EMI) or N-methyl-N-propylpyrrolidinium (P-13) as a cation was used as an electrolyte.
TL;DR: A new type of "task specific ionic liquid" was synthesized by the reaction of tetrabutylphosphonium hydroxide with amino acids, including glycine, L-alanine, T(C4)4][AA), and no changes in absorption capacity and kinetics were found after four cycles of absorption/desorption.
Abstract: A new type of "task specific ionic liquid", tetrabutylphosphonium amino acid [P(C 4 ) 4 ][AA], was synthesized by the reaction of tetrabutylphosphonium hydroxide [P(C 4 ) 4 ][OH] with amino acids, including glycine, L-alanine, L-β-alanine, L-serine, and L-lysine. The liquids produced were characterized by NMR, IR spectroscopies, and elemental analysis, and their thermal decomposition temperature, glass transition temperature, electrical conductivity, density, and viscosity were recorded in detail. The [P(C 4 ) 4 ][AA] supported on porous silica gel effected fast and reversible CO 2 absorption when compared with bubbling CO 2 into the bulk of the ionic liquid. No changes in absorption capacity and kinetics were found after four cycles of absorption/ desorption. The CO 2 absorption capacity at equilibrium was 50 mol % of the ionic liquids. In the presence of water (1 wt%), the ionic liquids could absorb equimolar amounts of CO 2 . The CO 2 absorption mechanisms of the ionic liquids with and without water were different.
TL;DR: In this work, the structures of cations, anions, and cation-anion ion-pairs of 1,3-dialkylimidazolium based ionic liquids were optimized systematically at the B3LYP/6-31+G level of DFT theory, and their most stable geometries were obtained.
Abstract: It is critically important to understand the structural properties of ionic liquids. In this work, the structures of cations, anions, and cation-anion ion-pairs of 1,3-dialkylimidazolium based ionic liquids were optimized systematically at the B3LYP/6-31+G* level of DFT theory, and their most stable geometries were obtained. It was found that there exist only one-hydrogen-bonded ion-pairs in single-atomic anion ionic liquids such as [emim]Cl and [emim]Br, while one- and two-hydrogen-bonded ion-pairs in multiple atomic anion ionic liquids such as [emim]BF4 and [emim]PF6 exist. Further studies showed that the cations and anions connect each other to form a hydrogen-bonded network in 1,3-dialkylimidazolium halides, which has been proven by experimental measurement. Furthermore, the correlation of melting points and the interaction energies was discussed for both the single atomic anion and multiple atomic anion ionic liquids.
TL;DR: In this article, the density and viscosity properties of binary mixtures of water and three ionic liquids were determined for binary systems, i.e., 1-ethyl-3-methylimidazolium ethylsulfate, 1-methyl-3methyloride-naphthalamide trifluoroacetate, and 1-ethyl-sulfonate, at atmospheric pressure and temperatures from (278.15 to 348.15) K.
Abstract: Density and viscosity were determined for binary mixtures of water and three ionic liquids: 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium trifluoroacetate, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. The experimental measurements of these properties were carried out at atmospheric pressure and temperatures from (278.15 to 348.15) K. The temperature dependence of density and viscosity for these systems can be described by an empirical second-order polynomial and by the Vogel−Fulcher−Tammann equation, respectively. Excess molar volumes and viscosity deviations were calculated and correlated by Redlich−Kister polynomial expansions. The latter correlations describe the variation of density and viscosity with composition. Comparison of the results for the three binary systems elucidates the influence of the anion on these physical properties.
TL;DR: A structural analysis on the solvation of nonpolar, polar, and associating solutes in imidazolium-based ionic liquids is performed, where this novel way of understanding their nature as microsegregated solvents is correlated with their ability to interact with different species in diverse and complex ways.
Abstract: The existence of microphase segregation between polar and nonpolar domains in ionic liquids changes the way in which solvation can be understood in these media. Here, we perform a structural analysis on the solvation of nonpolar, polar, and associating solutes in imidazolium-based ionic liquids, where this novel way of understanding their nature as microsegregated solvents is correlated with their ability to interact with different species in diverse and complex ways.
TL;DR: It was found that simple structural modifications provide a mechanism to manipulate, over a wide range, the temperature at which phase transitions occur and to specifically tailor physicochemical properties for potential end-use applications.
Abstract: The phase behavior, including glass, devitrification, solid crystal melting, and liquid boiling transitions, and physicochemical properties, including density, refractive index, viscosity, conductivity, and air−liquid surface tension, of a series of 25 protic ionic liquids and protic fused salts are presented along with structure−property comparisons. The protic fused salts were mostly liquid at room temperature, and many exhibited a glass transition occurring at low temperatures between −114 and −44 °C, and high fragility, with many having low viscosities, down to as low as 17 mPa·s at 25 °C, and ionic conductivities up to 43.8 S/cm at 25 °C. These protic solvents are easily prepared through the stoichiometric combination of a primary amine and Bronsted acid. They have poor ionic behavior when compared to the far more studied aprotic ionic liquids. However, some of the other physicochemical properties possessed by these solvents are highly promising and it is anticipated that these, or analogous protic s...
TL;DR: The electronic properties of gas-phase 1-butyl-3-methylimidazolium Cl ion pairs, [C(4)C(1)im]Cl, are analysed in order to deepen the understanding of ionic liquids in general.
Abstract: In this paper we analyse the electronic properties of gas-phase 1-butyl-3-methylimidazolium Cl ion pairs, [C(4)C(1)im]Cl, in order to deepen our understanding of ionic liquids in general. Examination of charge densities, natural bond orbitals (NBO), and delocalised molecular orbitals computed at the B3LYP and MP2/6-31(++)G(d,p) levels have enabled us to explain a number of experimental phenomena: the relative acidity of different sites on the imidazolium ring, variations in hydrogen-bond donor and acceptor abilities, the apparent contradiction of the hydrogen-bond-donor parameters for different types of solute, the low probability of finding a Cl(-) anion at the rear of the imidazolium ring and the expansion of the imidazolium ring in the presence of a strong hydrogen-bond acceptor. The unreactive but coordinating environment and large electrochemical window have also been accounted for, as has the strong electron-donating character of the carbon atoms to the rear of the ring in associated imidazolylidenes. The electronic structure of the [C(4)C(1)im](+) cation is best described by a C(4)==C(5) double bond at the rear, and a delocalised three-centre 4 e(-) component across the front (N(1)-C(2)-N(3)) of the imidazolium ring; delocalisation between these regions is also significant. Hydrogen-bond formation is driven by Coulombic stabilisation, which compensates for an associated destabilisation of the electronic part of the system. Interactions are dominated by a large positive charge at C(2) and the build up of pi-electron density above and below the ring, particularly that associated with the double bond between C(4) and C(5). The NBO partial charges have been computed and compared with those used in a number of classical simulations.
TL;DR: Ionic liquids which are (weak) Lewis bases have a number of interesting and useful properties different to those of traditional ionic liquids, including volatility and the possibility of being distillable in some cases and a base catalysis effect in others.