Alkylimidazolium Cations Research Articles

Simultaneous Determination of Ionic Liquid Cations and Anions Using Ion Chromatography with Tandem Ion Exchange Columns: a Preliminary Assessment

The usefulness of a cation exchange system followed by conductometric detection for alkylimidazolium cations separation and analysis was found for the first time. Furthermore, the possibility of simultaneously separating cations and anions typically used in ionic liquids in one chromatographic run was tested. A tandem of columns containing silica-based strong anion exchange and strong cation exchange packings was used. The study's objective was to find the optimal mobile phase: the best results were obtained with one consisting of potassium hydrogen phthalate and phthalic acid modified with acetonitrile. The method is simple and selective, and is believed to be applicable to numerous ionic liquids based on a similar design.

Effect of alkylimidazolium substituents on enantioseparation ability of single-isomer alkylimidazolium-β-cyclodextrin derivatives in capillary electrophoresis

A family of 6-mono(3-alkylimidazolium)-β-cyclodextrins with one primary hydroxyl group replaced by an alkylimidazolium cation has been developed. The effect of alkyl substitutents on the enantioresolution ability of these single-isomer cyclodextrins towards dansyl amino acids has been studied by capillary electrophoresis. Systematical investigations on the effect of buffer pH and selector concentration on the enatioseparation show that chiral selectors with a shorter alkyl chain (R = C n H 2 n+1 , n ≤ 4) presented more powerful chiral recognition ability. These newly introduced single-isomer β-cyclodextrin derivatives proved to be effective chiral selectors for most selected dansyl amino acids at low buffer pH (e.g. pH 5.0) with selector concentration no less than 3 mM. The apparent complex stability constants between alkylimidazolium β-CDs and dansyl amino acids were also theoretically determined by using the mobility difference model proposed by Wren and Rowe. The side alkyl chains from both dansyl amino acids and alkylimidazolium β-CDs displayed significant effect on the apparent complex stability constants. Both the optimum selector concentrations calculated according to the model, however, were much lower than the experimental values giving the maximum chiral resolution of enantiomers.

Proton-conducting ionic liquids based upon multivalent anions and alkylimidazolium cations

Alkylimidazolium type ionic liquids have been prepared with acidic anions derived from multivalent anions with the expectation of excellent thermal properties and ionic conductivity, including proton conduction.

Nonmolecular Solvents in Separation Methods: Dual Nature of Room Temperature Ionic Liquids

Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects. Nine different alkyl-methyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF(4-) or PF(6-) anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C18 column. It is shown with sodium salts and an acetonitrile-water 30/70 v/v mobile phase that anions can adsorb on the stationary phase surface according to their lyotropic character. They can also form ion pairs with the cationic basic solutes. Alkyl-imidazolium cations also adsorb on the C18 bonded stationary phase due to hydrophobic character depending on their alkyl chain length. Anion adsorption dramatically increases the cationic solute retention factors when cation adsorption decreases them. The cation adsorption is mainly responsible for peak shape and efficiency enhancements. RTILs are additives that enhance the basic cationic solute peak shape changing peak position. A wise choice of the appropriate combination of anion lyotropy with imidazolium cation hydrophobicity allows playing with solute selectivity and analysis duration.

Preliminary Assessment of the Sorption of some Alkyl Imidazolium Cations as used in Ionic Liquids to Soils and Sediments

The growing interest in the use of ionic liquids may soon result in their presence in the environment. In any evaluation of the environmental fate of these compounds, their sorption on soil is an essential parameter. This paper reports data on the sorption of ionic liquids on selected soils and marine sediments. Batch-equilibrium adsorption tests were conducted on a selection of imidazolium ionic liquid entities. All the compounds were strongly sorbed on all the soils under study. It seems that, regardless of the hydrophobic interaction with organic matter, non-hydrophobic interactions contribute to the sorption of these compounds to soils and sediments, which usually tends to occur with highly polar ionized groups such as quaternary moieties.

The structures of alkylimidazolium fluorohydrogenate molten salts studied by high-energy X-ray diffraction

The structures of a series of XF·2.3HF (X=1-methylimidazolium, 1-ethyl-3-methylimidazolium (EMI), 1-butyl-3-methylimidazolium, 1-hexyl-3-methyl-imidazolium (HMI)) room temperature molten salts have been investigated by the high-energy synchrotron X-ray diffraction technique. The correlation peaks appearing in the total correlation function are mainly ascribed to an intra-molecular correlation of alkylimidazolium cations. However, it is suggested that the peak near 3.6 Å is ascribed not only to intra-molecular but also inter-molecular correlations of the cation. The contribution of the latter is also supported by the first sharp diffraction peak of the total structure factor found at almost the same position as that of a Bragg peak in the simulated X-ray diffraction pattern of solid EMIF·HF with a layered structure, corresponding to the layer separation.

An improved preparation of 1,3-dialkylimidazolium tetrafluoroborate ionic liquids using microwaves

An efficient microwave protocol is described for the preparation of room temperature ionic liquids consisting of alkyl imidazolium cations bearing tetrafluoroborate as anions.

ChemInform Abstract: Room Temperature Ionic Liquids of Alkylimidazolium Cations and Fluoroanions

Abstract The preparation, physical and chemical properties, and application of ionic liquids at ambient conditions are reviewed focusing on the salts of alkylimidazolium cations and fluoroanions.