Expanding the useful range of ionic liquids: melting point depression of organic salts with carbon dioxide for biphasic catalytic reactions

Large and previously unreported melting point depressions (even exceeding DeltaTm of 100 degrees C) were observed for simple ammonium and phosphonium salts in the presence of compressed CO2, bringing them well within the range of typical ionic liquids; possible applications include biphasic catalysis in IL/scCO2 systems as demonstrated for rhodium complex catalyzed hydrogenation, hydroformylation, and hydroboration of 2-vinyl-naphthalene using a CO2-induced molten sample of [NBu4][BF4] as a catalyst phase at temperatures in the range of 55-75 degrees C, i.e. 100 degrees C below the normal melting point of the organic salt.     

Melting point depression of ionic liquids confined in nanospaces

A new physical method was proposed to control the liquid properties of room temperature ionic liquids (RT-ILs) in combination with nanoporous materials; the melting point of ILs confined in nanopores remarkably decreases in proportion to the inverse of the pore size.     

Laterally fluorinated tolanes of low melting point

Tolanes having a terminal polar group and a lateral fluoro substituent are reported with the desirable features of high birefringence, wide nematic range and low melting point.     

High-pressure CO2-induced reduction of the melting temperature of ionic liquids

An in situ ATR-IR spectroscopic study has shown that high-pressure CO2 reduces melting temperature of ionic liquids such as [C16mim][PF6].     

Choline saccharinate and choline acesulfamate: ionic liquids with low toxicities

Choline saccharinate and choline acesulfamate are two examples of hydrophilic ionic liquids, which can be prepared from easily available starting materials (choline chloride and a non-nutritive sweetener). The (eco)toxicity of these ionic liquids in aqueous solution is very low in comparison to other types of ionic liquids. A general method for the synthesis and purification of hydrophilic ionic liquids is presented. The method consists of a silver-free metathesis reaction, followed by purification of the ionic liquid by ion-exchange chromatography. The crystal structures show a marked difference in hydrogen bonding between the two ionic liquids, although the saccharinate and the acesulfamate anions show structural similarities. The optimized structures, the energetics, and the charge distribution of cation-anion pairs in the ionic liquids were studied by density functional theory (DFT) and second-order (M?ller-Plesset) perturbation theory calculations. The occupation of the non-Lewis orbitals was considered to obtain a qualitative picture of the Lewis structures. The calculated interaction energies and the dipole moments for the ion pairs in the gas phase were discussed.     

Novel inorganic ionic liquids possessing low melting temperatures and wide electrochemical windows: Binary mixtures of alkali bis(fluorosulfonyl)amides

Thermal properties of alkali bis(fluorosulfonyl)amides, MFSI (M = Li, Na, K, Rb, Cs), have been investigated. Binary phase diagrams of LiFSI–KFSI and NaFSI–KFSI systems have been constructed. Eutectic point for LiFSI–KFSI is 338 K at (x_Li, x_K) = (0.45, 0.55) and, that for NaFSI–KFSI is 330 K at (x_Na, x_K) = (0.45, 0.55). The electrochemical window of the eutectic LiFSI–KFSI is as wide as 6.0 V at 348 K with the cathode limit being lithium metal deposition. The electrochemical window of the eutectic NaFSI–KFSI is 5.0 V at 340 K with sodium metal deposition at the cathode limit. These new inorganic ionic liquids are highly promising for various electrochemical applications.     

Tetraalkylammonium amino acids as functionalized ionic liquids of low viscosity

Four of nine tetraalkylammonium-based amino-acid ionic liquids prepared in this work show lower viscosities than all amino acid-based ionic liquids found in the literature and their reversible CO(2) absorption approaches 0.5 mol per mol ionic liquid.     

Microwave-assisted separation of ionic liquids from aqueous solution of ionic liquids

Microwave-assisted separation has been applied to recover ionic liquid (IL) from its aqueous solution as an efficient method with respect to time and energy compared to the conventional vacuum distillation. Hydrophilic ILs such as 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][TfO]) and 1-ethyl-3-methylimidazolium methylsulfate ([Emim][MS]) could be recovered in 6 min from the mixture of ILs and water (1:1, w/w) under microwave irradiation at constant power of 10 W while it took at least 240 min to obtain ILs containing same water content (less than 0.5 wt%) by conventional vacuum oven at 363.15 K with 90 kPa of vacuum pressure. Energy consumptions per gram of evaporated water from the homogeneous mixture of hydrophilic ILs and water (1:1, w/w) by microwave-assisted separation were at least 52 times more efficient than those in conventional vacuum oven. It demonstrated that microwave-assisted separation could be used for complete recovery of ILs in sense of time and energy as well as relevant purity.     

Trialkylsulfonium dicyanamides--a new family of ionic liquids with very low viscosities

Trialkylsulfonium dicyanamides show surprisingly low viscosities down to -20 degrees C and are therefore highly interesting liquid materials for separation processes and electrolyte applications at low temperatures.     

Low-viscosity and low-melting point asymmetric trialkylsulfonium based ionic liquids as potential electrolytes

Nine new ionic liquids based on small asymmetric trialkylsulfonium cations with TFSI⁻ anion were prepared and characterized. Physical and electrochemical properties of these ionic liquids, including melting point, thermal stability, viscosity, conductivity and electrochemical window were determined. Reducing symmetry of cations reduces the melting points of these ILs. Some of these hydrophobic ionic liquids showed low-viscosity and low-melting point characteristics. The viscosities of S₂₂₃TFSI, S₂₂₁TFSI and S₁₂₃TFSI were 33, 36 and 39 mPa s at 25 °C, respectively. Electrochemical and thermal stabilities of these ILs permitted them to become promising electrolytes used in electrochemical devices.     

Low melting and slightly viscous ionic liquids via protonation of trialkylamines by perfluoroalkyl β-diketones

New trialkylammonium perfluoroalkyl β-diketonate salts are obtained in one-step reactions by taking advantage of proton transfer from perfluoroalkyl β-diketones to tertiary amines. The charge associated with the β-diketonate anion is considerably delocalized, which may play a role in giving rise to low melting and thermally stable salts with low viscosities and densities.     

Room temperature ionic liquids containing low water concentrations-a molecular dynamics study

We have performed classical molecular dynamics to study the properties of a water-miscible and a water-immiscible room-temperature ionic liquid when mixed with small quantities of water. The two ionic liquids consist of the same 1-ethyl-3-methylimidazolium ([EMIM]) cation combined with either the boron tetrafluoride ([BF(4)]) or bis(trifluoromethylsulfonyl)imide ([NTf(2)]) anion. It is found that, in both ionic liquids, water clusters of varying sizes are typically hydrogen bonded to two anions with the cation playing a minor role. We also highlight the difficulties of obtaining dynamic quantities such as self-diffusion coefficients from simulations of such viscous systems.     

Vapourisation of ionic liquids

Eight common imidazolium based ionic liquids have been successfully evaporated in ultra-high vacuum, their vapours analysed by line of sight mass spectrometry and their heats (enthalpy) of vapourisation determined. They were found to evaporate as ion pairs, with heats of vapourisation which depend primarily on the coulombic interactions within the liquid phase and the gas phase ion pair. An electrostatic model is presented relating the heats of vapourisation to the molar volumes of the ionic liquids.     

Applications of ionic liquids

Ionic liquids have recently gained popularity in the scientific community owing to their special properties and characteristics. One of the reasons why ionic liquids have been termed “green solvents” is due to their negligible vapour pressure. Their use in electrochemical, biological and metal extraction applications is discussed. Wide research has been carried out for their use in batteries, solar panels, fuel cells, drug deliveries and biomass pretreatments. This work aims to consolidate the various findings from previous works in these areas. DOI 10.1002/tcr.201100036     

Reactivity of ionic liquids

Ionic liquids are becoming widely used in synthetic organic chemistry and yet relatively little attention has been paid to the intrinsic reactivity of these low temperature molten salts. Clues to the non-innocent nature of many ionic liquids are contained in the reports of altered reactivity of dissolved substrates, unexpected catalytic activity and unforeseen by-product formation. In this review, we focus on the reactivity of ionic liquids, as opposed to reactivity in ionic liquids (although discussion of the latter is often included where it aids understanding of the former).     

Electrowetting of ionic liquids

We have successfully demonstrated that imidazolium- and pyrrolidinium-based commercial room-temperature ionic liquids can electrowet (with a dc voltage) a smooth fluoropolymer (Teflon AF1600) surface. Qualitatively, the process is analogous to the electrowetting of aqueous electrolyte solutions: the contact angle versus voltage curve has a parabolic shape which saturates at larger voltages (positive or negative). On the other hand we observed several peculiarities: (i) the efficiency is significantly lower (by about an order of magnitude); (ii) the influence of the bulky cation is larger and the importance of the smaller anion is lesser, especially with respect to electrowetting saturation; (iii) there is an asymmetry in the saturation contact angles found for positive and negative voltages. The asymmetry may be correlated with the cation-anion asymmetry of the ionic liquids. The low efficiency may be caused by the presence of water and other impurities in these commercial materials.     

Nicotine: on the potential role of ionic liquids for its processing and purification

Marked solubility differences of nicotine in the ionic liquids [C(2)mim][NTf(2)], [C(2)mim][EtOSO(3)], and [C(n)mim]Cl, 6 相似文献