On the ideality of binary mixtures of ionic liquids

In this work, structural and dynamical properties of the binary mixture of 1-ethyl-3-methyl-imidazolium chloride and 1-ethyl-3-methyl-imidazolium thiocyanate are investigated from ab initio molecular dynamics simulations and compared to the pure ionic liquids. Furthermore, the binary mixture is simulated with two different densities to gain insight into how the selected density affects the different properties. In addition, a simple NMR experiment is carried out to investigate the changes of the chemical shifts of the hydrogen atoms due to the composition of the mixture.     

Transition metal catalysed dehydrogenation of amine-borane fuel blends

Mixtures containing ammonia-borane and sec-butylamine-borane remain liquid throughout the hydrogen release process that affords tri(N-sec-butyl)borazine and polyborazylene. Concentrated solutions with metal catalysts afford >5 wt% H(2) in 1 h at 80 °C and addition of (EMIM)EtSO(4) ionic liquid co-solvent eliminates competing formation of insoluble linear poly(aminoborane) (EMIM = 1-ethyl-3-methyl-imidazolium).     

离子液体/凝胶聚合物电解质的制备及其与LiFePO_4的相容性

以1-甲基-3-乙基咪唑六氟磷酸盐(EMIPF6)、聚偏氟乙烯-六氟丙烯(P(VDF-HFP))和六氟磷酸锂(LiPF6)为原料,采用溶液浇铸法制备了离子液体/凝胶聚合物电解质(ILGPE).通过循环伏安(CV)、计时电流法、恒流充放电、电化学阻抗法(EIS)研究了该电解质的离子传输特性以及与锂离子电池正极材料LiFePO4的相容性.结果表明,离子液体/凝胶聚合物电解质的室温电导率为1.650×10-3S·cm-1,电化学稳定窗口达到5.0V.在充放电循环过程中,电极表面形成的钝化膜改善了锂离子脱、嵌可逆性和电极/电解质的界面性质.     

Measurement of vapor–liquid equilibria (VLE) and excess enthalpies (H) of binary systems with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and prediction of these properties and γ using modified UNIFAC (Dortmund)

Vapor–liquid equilibria (VLE) and excess enthalpies (H^E) were measured for a variety of alkanes, alkenes, aromatics, alcohols, ketones and water in several ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM]⁺[BTI]⁻, 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [BMIM]⁺[BTI]⁻, 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [HMIM]⁺[BTI]⁻ and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [OMIM]⁺[BTI]⁻, covering the temperature range from 323.15 to 413.15 K. The new data were used together with the already available experimental data for imidazolium compounds to fit the required group interaction parameters for modified UNIFAC (Dortmund). The results show that in the future modified UNIFAC (Dortmund) can be applied successfully also for systems with ionic liquids.     

半胱氨酸阴离子与咪唑阳离子间相互作用的理论研究

采用密度泛函理论在B3LYP/6-311＋G(d,p)水平上对1-乙基-3-甲基咪唑阳离子和半胱氨酸阴离子形成的气态阴阳离子对([Emim][Cys])进行理论研究. 通过几何结构优化以及频率分析得到势能面上7个稳定的离子对构型. 计算结果表明[Emim]＋和[Cys]－之间存在较强的氢键相互作用, 其稳定化能主要来源于[Cys]－中羰基O的孤对电子lp(O) 和[Emim]＋中C—H反键轨道 s*(C—H) 之间的相互作用, lp(O)®s*(C—H). [Emim][Cys]_S1是最稳定的离子对构型, 考虑BSSE的相互作用能为－387.66 kJ/mol. 从NPA和NBO分析以及AIM (Atoms in Molecules)计算等方面阐述了半胱氨酸阴离子与咪唑阳离子之间氢键相互作用的本质, 并初步探讨了阴阳离子对相互作用对氨基酸离子液体性质的影响.     

A new force field model for the simulation of transport properties of imidazolium-based ionic liquids

A new, non-polarizable force field model (FFM) for imidazolium-based, room-temperature ionic liquids (RTILs), 1-ethyl-3-methyl-imidazolium tetrafluoroborate and 1-butyl-3-methyl-imidazolium tetrafluoroborate, has been developed. Modifying the FFM originally designed by Liu et al. (J. Phys. Chem. B, 2004, 108, 12978-12989), the electrostatic charges on interacting sites are refined according to partial charges calculated by explicit-ion density functional theory. The refined FFM reproduces experimental heats of vaporization, diffusion coefficients, ionic conductivities, and shear viscosities of RTILs, which is a significant improvement over the original model (Zh. Liu, Sh. Huang and W. Wang, J. Phys. Chem. B, 2004, 108, 12978-12989). The advantages of the proposed procedure include clarity, simplicity, and flexibility. Expanding the functionality of our FFM conveniently only requires modification of the electrostatic charges. Our FFM can be extended to other classes of RTILs as well as condensed matter systems in which the ionic interaction requires an account of polarization effects.     

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinm?ller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. H?fft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.     

Effect of Ionic Liquids as Mobile-Phase Additives on Chromatographic Parameters of Neuroleptic Drugs in Reversed-Phase High-Performance Liquid Chromatography

Abstract

Ionogenic basic compounds belonging to phenothiazine derivatives were analyzed in the reversed-phase system and were modified with the addition of three ionic liquids: 1-ethyl-3-methyl-imidazolium hexafluorophospate (EMIM PF₆), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM PF₆), and 1-butyl-3-methyl-imidazolium chloride (BMIM Cl). The effects of the concentration and the type of ionic liquid on the analytes' retention, peak symmetry, and efficiency were examined. The following trends increase analytes' retention factor and improve system efficiency: BMIM PF₆ > EMIM PF6 > BMIM Cl. With its asymmetric cation enlarged with hydrophobic substituents and a chaotropic anion, BMIM PF₆ appeared to be the most advantageous one. The isotherm of adsorption of this reagent presents a typical Langmuir course. By the application of high-performance liquid chromatography, lipophilicity parameters were established (lnk_w, S, ? ₀) for the investigated compounds. Chromatographic systems modified with ionic liquids were compared to buffered organic–aqueous mobile phase and eluent containing chaotropic salt additive.     

On the computation and contribution of conductivity in molecular ionic liquids

In this study we present the results of the molecular dynamics simulation of the ionic liquids: 1-butyl-3-methyl-imidazolium tetrafluoroborate and trifluoromethylacetate as well as 1-ethyl-3-methyl-imidazolium dicyanamide. Ionic liquids are characterized by both a molecular dipole moment and a net charge. Thus, in contrast to a solution of simple ions in a (non-) polar solvent, rotational and translational effects influence the very same molecule. This study works out the theoretical framework necessary to compute the conductivity spectrum and its low frequency limit of ionic liquids. Merging these computed conductivity spectra with previous simulation results on the dielectric spectra of ionic liquids yields the spectrum of the generalized dielectric constant, which may be compared to experiments. This spectrum was calculated for the three ionic liquids over six orders of magnitude in frequency ranging from 10 MHz to 50 THz. The role of rotation and translation and their coupling term on the generalized dielectric constant is discussed in detail with a special emphasis on the zero-frequency limit. Thereby, the frequency dependence of the cross correlation between the collective rotational dipole moment and the current is discussed.     

Reactions of perfluorinated 1-ethyltetrahydronaphthalene, 1-ethylindan, and 1,1-diethylindan with pentafluorobenzene in antimony pentafluoride

The reaction of perfluoro(1-ethyltetrahydronaphthalene) with pentafluorobenzene in SbF₅, followed by treatment of the reaction mixture with water, afforded a mixture of 1-hydroxyperfluoro(1-phenyl-4-ethyletetrahydronaphthalene) and perfluoro(5-phenyl-8-ethyl-2,6,7,8-tetrahydronaphthalen-2-one). From perfluoro(1,1-diethylindan), 1-hydroxyperfluoro(1,1-diethyl-3-phenylindan) was obtained. Perfluoro(1-ethylindan) reacted with an equimolar amount of pentafluorobenzene in SbF₅ to give (after hydrolysis) 1-hydroxyperfluoro-(3-ethyl-1-phenylindan), 1-hydroxyperfluoro(3-ethyl-1,3-diphenylindan), and perfluoro(1-ethyl-1-phenylindan), while in the reaction with excess pentafluorobenzene, followed by treatment with anhydrous hydrogen fluoride, perfluoro(1-ethyl-3-phenylindan) and perfluoro(1-ethyl-1,3-diphenylindan) were formed.     

Dynamic coating of a capillary with room-temperature ionic liquids for the separation of amino acids and acid drugs by capillary electrophoresis

A room-temperature ionic liquid (IL), 1-ethyl-3-methyl-imidazolium tetrafluoroborate (1E-3MI-TFB), used for the coating of a silica capillary enables one to reduce or invert the electroosmotic flow (EOF) in capillary zone electrophoresis. Excellent separations of amino acids and ary lalkanoic acids were obtained. Such separations could not be obtained in a naked capillary in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) or polycationic polymer hexadimethrine bromide (HDB). The results indicate that 1E-3MI-TFB not only modulates the EOF but also acts as a discriminator. Further experiments indicate that the interaction between hydrogen at C-2 carbon of IL and acid drugs plays an important role in the separation. The text was submitted by the authors in English.     

A DFT study on the double bond migration of butene catalyzed by ionic pair of 1-ethyl-3-methyl-imidazolium fluoride

The double bond migration of butene catalyzed by 1-ethyl-3-methyl-imidazolium fluoride (EmimF) has been studied using quantum chemical method. The geometries of reactant, transition state and product for the isomerization have been optimized by density functional theory (DFT) at the B3PW91/6-31G(d,p), 6-311++G(d,p) and aug-cc-PVDZ levels. The computed results show that the 4-H atom on imidazole ring of EmimF has a good catalytic activity to the double bond migration of butene and the catalytic reaction of 1-butene to 2-butene is a synergetic and elementary process. The apparent activation energy of isomerization is about 197 kJ/mol.     

Selected Imidazolium Ionic Liquids as a Terminating Electrolyte in Isotachophoresis

Results of application of selected imidazolium ionic liquids [especially EMIM (1-ethyl-3-methyl-imidazolium) cation] as a new type of terminating electrolyte (TE) in isotachophoresis (ITP) with conductometric detection are presented. In experiments seven different types of leading electrolyte (LE) with new terminating electrolyte were studied. After selection of parameters influenced on the analysis resolution, buffers were successfully used in control of qualitative and quantitative analysis (sodium, potassium, calcium, and magnesium) of different type of waters. The new ITP method was satisfying and basic validation parameters were assigned.     

Reactions of tetrafluoroethene oligomers. Part 5. Some reactions of perfluoro-[(1-ethyl-1-methylpropyl)(1-methylpropyl)] keten

The title keten (1) was treated with some alcohols and amines: methanol afforded an inseparable mixture of two products, 4H-4-methoxycarbonyl-docosafluoro-3,5-dimethyl-3-ethylheptane (2) and 4-methoxycarbonyl-heneicosafluoro-3,5-dimethyl-8-ethylhept-3-ene (3). Treatment of the mixture with sodium hydroxide afforded pure (3). Reaction of (1) with benzyl alcohol yielded 4-benzyloxycarbonyl-4H-docosafluoro-3,5-dimethyl-3-ethylheptane (4) which on hydrogenation gave a mixture of 4H-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (5) and 4H-docosafluoro-3,5-dimethyl-3-ethyl-heptane-4-carboxylic acid (6). Reaction of (1) with ammonia yielded 4-carbonamido-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (7) and dimethylamine similarly afforded the N,N-dimethyl analogue (9). However, reaction of (1) with ethylamine gave an unusual cyclisation product, 1-ethyl-3H-heneicosafluoro-4-ethyl-4-methyl-3(1-ethyl-1-methylpropyl)azetan-2-one (8).     

Skeletal transformations of perfluoro-1-ethyl-1-phenylbenzocyclobutene in the reaction with antimony pentafluoride

Interaction of perfluoro-1-ethyl-1-phenylbenzocyclobutene with SbF₅ at room temperature gives, after treatment of the reaction mixture with H₂O, perfluoro-4-[1-(2-methylphenyl)propylidene]cyclohexa-2,5-dienone as a main product. The reaction at 90-95 °C leads, after treatment with H₂O, to a mixture of perfluorinated 9-ethyl-9-methyl-1,2,3,4-tetrahydro-9H-fluorene, 9-ethyl-4a-methyl-4,4a-dihydrofluoren-1-one, 3-ethyl-3-phenylphthalide, 1-hydroxy-2-methyl-1-phenylindan, 3-methyl-2-phenylindenone and small amounts of other products.     

Synthesis of a novel analog of nalidixic acid: 1-Ethyl-1,4-dihydro-4-oxo-7-(trifluororaethyl)-1,8-naphthyridine- 3-carboxylic acid

Reaction of nalidixic acid ( 1 ) with thionyl chloride and subsequent treatment with ethanol gave a mixture of ethyl 1-ethyl-1,4-dihydro-4-oxo-7-(trichloromethyl)-1,8-naphthyridine-3-carboxylate ( 3 ) and diethyl 1-ethyl-1,4-dihydro-4-oxo-1,8-naphthyridine-3,7-dicarboxylate ( 4 ). Ethyl1-ethyl-1,4-dihydro-4-oxo-7-(trichloromethyl)-1,8-naphthyridine-3-carboxylate ( 3 ) was reacted with antimony pentafluoride to afford 1-ethyl-1,4-dihydro-4-oxo-7-(trifluoromethyl)-l,8-naphthyridine-3-carboxylic acid ( 5 ).     

Viscosity of n-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids saturated with compressed CO2

The viscosity of imidazolium-based ionic liquids (ILs) saturated with gaseous, liquid and supercritical carbon dioxide (CO₂) was measured by a high-pressure viscometer at three different temperatures (25, 50, and 70 °C). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1-n-hexyl-3-methylimidazolium ([HMIm]), and 1-n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)amide ([Tf₂N]), saturated with CO₂ was measured up to a maximum of 287 bar. As CO₂ pressure is increased the viscosity of the IL mixture dramatically decreases. While, the ambient pressure viscosity of 1-alkyl-3-methyl-imidazolium [Tf₂N] ILs increases significantly with increasing chain length, the viscosity of all the CO₂-saturated ILs becomes very similar at high CO₂ pressures. From previous vapor–liquid equilibrium data, the viscosity with concentration was determined and found to be the primary factor to describe the fractional viscosity reduction. Several predictive and correlative methods were investigated for the mixture viscosity given pure component properties and include arithmetic mixing rules, the Irving (Predictive Arrhenius) model, Grunberg equation, etc. The modified Grunberg model with one adjustable parameter provided an adequate fit to the data.     

High-pressure phase equilibria of {carbon dioxide (CO2) + n-alkyl-imidazolium bis(trifluoromethylsulfonyl)amide} ionic liquids

Ionic liquids (ILs) and carbon dioxide (CO₂) systems have unique phase behavior that has been applied to applications in reactions, extractions, materials, etc. Detailed phase equilibria and modeling are highly desired for their further development. In this work, the (vapor + liquid) equilibrium, (vapor + liquid + liquid) equilibrium, and (liquid + liquid) equilibrium of n-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids with CO₂ were measured at temperatures of (298.15, 323.15, 343.15) K and pressure up to 25 MPa. With a constant anion of bis(trifluoromethylsulfonyl)amide, the n-alkyl chain length on the cation was varied from 1-ethyl-3-methyl-imidazolium ([EMIm][Tf₂N]), 1-hexyl-3-methyl-imidazolium ([HMIm][Tf₂N]), to 1-decyl-3-methyl-imidazolium ([DMIm][Tf₂N]). The effects of the cation on the phase behavior and CO₂ solubility were investigated. The longer alkyl chain lengths increase the CO₂ solubility. The Peng–Robinson equation of state with van der Waals 2-parameter mixing rule with estimated IL critical properties were used to model and correlate the experimental data. The models correlate the (vapor + liquid) equilibrium and (liquid + liquid) equilibrium very well. However, extrapolation of the model to much higher pressures (>30 MPa) can results in the prediction of a mixture critical point which, as of yet, has not been found in the literature.     

Measurement and prediction of vapor–liquid equilibria of ternary systems containing ionic liquids

For the first time vapor–liquid equilibrium (VLE) data for ternary systems containing ionic liquids are reported. The data were measured by means of a computer-operated static VLE apparatus at 353.15 K with the ionic liquids 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [EMIM]⁺[(CF₃SO₂)₂N]⁻ and 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [BMIM]⁺[(CF₃SO₂)₂N]⁻ and acetone, 2-propanol and water. The experimental VLE data of the binary systems were correlated using the Wilson, NRTL and UNIQUAC models. The errors using Wilson, NRTL, and UNIQUAC are 3.92%, 1.45%, and 1.53%. The g^E-model parameters of the binary systems were used to predict the VLE behavior of the ternary systems and the predictions were compared to the experimental datasets. The errors using Wilson-, NRTL-, and UNIQUAC-parameters are 5.61%, 7.22%, and 5.02%.     

Theoretical studies on the butene double bond isomerization catalyzed by 5-H of 1-ethyl-3-methyl-imidazolium fluoride

The isomerization of 1-butene to trans-2-butene catalyzed by 5-H proton of 1-ethyl-3-methyl-imidazolium fluoride (EMImF) has been studied with density functional theory of quantum chemistry. The equilibrium states geometries and transition state geometry are optimized at the levels of B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p), respectively. The apparent activation barrier of isomerization is about 208 kJ/mol theoretically. It indicates that the 5-H proton on the imidazole ring of EMImF has certain catalytic activity to the butene double bond isomerization, which is similar to that of the 4-H proton. According to the data of intrinsic coordinate path, it can be determined that the isomerization is an elementary course and the hydrogen exchange of butene with EMImF is synergetic.