Thermodynamics of cesium complexes formation with 18-crown-6 in ionic liquids

Thermodynamic data for cesium complexes formation with 18-crown-6 (18C6, L) [Cs(18C6)]⁺ in N-butyl-4-methyl-pyridinium tetrafluoroborate ([BMPy][BF₄], I), in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄], II) and in 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)₂], III) were measured with NMR ¹³³Cs technique at 23–50 °C. The stability of cesium complex in RTILs is estimated to be in the range between water and DMFA. Stability constants for [Cs(18C6)]⁺ are found to decrease as temperature is increasing. The following values for lgK(Cs+L) and ΔH(Cs+L) at 23 °C are determined: 2.6 (0.3), ?47(1) kJ/mol (RTIL I); 2.8(0.3), ?80(3) kJ/mol (RTIL II) and 3.03 (0.08), ?47(2) kJ/mol (RTIL III). It is demonstrated that enthalpy change promotes complex formation while the corresponding change of entropy is negative and provides decomposition of [Cs(18C6)]⁺.     

The Synthesis of Anatase TiO2 Nanoparticles by Solvothermal Method using Ionic Liquid as Additive

The solvothermal reactions of Ti(OiPr)₄ in alcohol using ionic liquid as additive were investigated. In the presence of [BMIM][Cl], [BMIM][Br], [BMIM][NTf₂], [BMIM][SO₃Me], [BMIM][SO₄Me], or [BMIM][OTf] (BMIM = 1‐Butyl‐3‐methylimidazolium), pure anatase nanoparticles were obtained. The controlled hydrolysis of Ti(OiPr)₄ in the presence of ionic liquids to form titanium oxo clusters plays a key role in the formation of anatase nanostructures, and ionic liquids can be repeatedly used to synthesise anatase nanoparticles. However, in the presence of [BMIM][PF₆], [BMIM]₂[Ti(OH)₆] was obtained by an anion exchange reaction.     

Stability of crown-ether complexes with alkali-metal ions in ionic liquid-water mixed solvents

Stability constants of sodium and cesium ion complexes with 18-crown-6 (18C6) and dibenzo-18-crown-6 (DB18C6) in N-butyl-4-methyl-pyridinium tetrafluoroborate [BMP][BF₄] aqueous solutions were measured using the ²³Na and ¹³³Cs NMR technique at 23 °C. To the best of our knowledge, the estimated values of stability constants reported in this study are the first such values given for ionic liquid solutions. The cationic exchange between the free and complexed species is rapid, and only formation of the 1:1 complexes [M(18C6)]⁺ and [M(DB18C6)]⁺ (M = Na⁺, Cs⁺) were observed. The complex formation constants demonstrated a strong dependence on the [BMP][BF₄] concentration. For [M(18C6)]⁺, in solutions with a 0.33–0.70 mole fraction of water in [BMP][BF₄], lg K values are found to be more than one unit higher than the lg K values measured in pure aqueous solutions, although no information concerning the influence of [BMP][BF₄] on the complex formation selectivity could be observed. DB18C6 complexes revealed significantly lower stability under the same conditions. An extrapolation to zero water content gave the lg K = 2.42 for [Cs(18C6)]⁺ in [BMP][BF₄]. It was discovered that when added to water, [BMP][BF₄] increases the solubility of crown ethers and decreases the solubility of alkali metal nitrates. Complex formation with crown ethers enhances the solubility of alkali metal salts in [BMP][BF₄].     

Synthesis of Carbonyl Compounds from Alcohols Using Electrochemically Generated Superoxide Ions in RTILs

Abstract

We show that the superoxide ion (O₂ ^??) generated electrochemically from oxygen dissolved in room-temperature ionic liquids (RTILs) reacts with primary and secondary alcohols to form the corresponding ketones and carboxylic acids, respectively. Specifically, we study the conversion of benzhydrol to benzophenone and benzyl alcohol to benzaldehyde/benzoic acid. The kinetics (e.g., rate, selectivity, and yield) for these reactions are also determined as functions of the variations in the structure of the ionic liquids. The RTILs used here are imidazolium-based cations where the functional groups on the imidazolium ring are modified. Specifically, 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆], 1-butyl-2,3-dimethylimidazolium hexafluorophosphate [bdmim][PF₆], and 1-hexyl-3-methylimidazolium hexafluorophosphate [hmim][PF₆] are used as the reaction medium. These results are compared to an ammonium-based RTIL (N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide). The results show that the nucleophilic attack by the O₂ ^?? of both the RTIL and the alcohol, especially that of the H atom at the R2 position of the [bmim][PF₆] and [hmim][PF₆], greatly affects the yields. No RTIL degradation products were detected for the reactions in [bdmim][PF₆] and N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide ionic liquids. For the benzyl alcohol oxidation reaction in the RTIL, N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide, benzaldehyde formed did not undergo further oxidation to form benzoic acid, which may be due to the greater hydrophobicity of this RTIL. The competitive reaction kinetics between the alcohol and RTIL component must be considered in the selection of the RTIL solvent system.     

Effect of ionic liquid organizing ability and amine structure on the rate and mechanism of base induced elimination of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes

The kinetics of the elimination reaction of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes into the corresponding 1,1-dibromo-2,2-bis(phenyl-substituted)ethenes induced by amines were studied in three room temperature ionic liquids ([BMIM][BF₄], [BMIM][PF₆], [BdMIM][BF₄]). In order to have information about reagent-ionic liquid interactions, the reaction was carried out over the temperature range (293.1-313.1 K). To study the effect of the amine on the rate and occurrence of the elimination reaction, several primary, secondary and tertiary amines with different structure (cyclic and acyclic), basicity and steric requirements were used. The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents. Furthermore, ionic liquids seem to be able to induce, for the studied reaction, a shift of mechanism from E1_cb (in MeOH) versus E2 (in ionic liquid).     

Isobaric vapor–liquid equilibria for ethanol–water system containing different ionic liquids at atmospheric pressure

Isobaric vapor–liquid equilibrium (VLE) data for ethanol–water systems containing ionic liquids (ILs) 1-methyl-3-methylimidazolium dimethylphosphate ([MMIM][DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), 1-butyl-3-methylimidazolium bromide ([BMIM][Br]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) at atmospheric pressure (101.32 kPa) were measured with a circulation still. The results showed that the VLE of ethanol–water systems in the presence of different ILs was obviously different from that of the IL-free system. All ILs studied showed a salting-out effect, which gave rise to a change of the relative volatility of ethanol, and even to an elimination of the azeotropic point. It was found that the salting-out effect followed the order of [BMIM][Cl] > [BMIM][Br] > [BMIM][PF₆] and [MMIM][DMP] > [EMIM][DEP], which was ascribed to the preferential solvation ability of the ions resulting from the dissociation of the IL.     

Photophysics and dynamics of a β-carboline analogue in room temperature ionic liquids

Room temperature ionic liquids are rapidly emerging as a new class of media that are ideally suited for various applications including carrying out chemical reactions. In the present article, we report the photophysics of a β-carboline analogue, namely, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), in three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO(4)]), 1-butyl-3-methylimidazolium octyl sulfate ([BMIM][C(8)SO(4)]) and 1-ethyl-3-methylimidazolium methyl sulfate ([EMIM][MeSO(4)]). Out of these, [BMIM][C(8)SO(4)] is a typical RTIL that forms micellar aggregates above a critical micellar concentration (CMC). Steady state absorption, steady state and time resolved fluorescence techniques are used to probe the properties of these systems. The investigation reveals that the photophysics of AODIQ is modified significantly in the micelle-forming RTIL as compared to that in the other two. A comparative study with the fluorophore in [BMIM][C(8)SO(4)] and a conventional anionic surfactant of a similar hydrophobic chain length from the sodium-n-alkyl sulfate series, viz., sodium octyl sulfate (S(8)S), reveals that the fluorophore experiences a more constrained environment in the RTIL micelle as compared to the conventional anionic micelle.     

The thermochemistry of solvation of imidazolium-based ionic liquids in benzene

ABSTRACT

The present work is devoted to the thermochemical study of solvation of ionic liquids (IL) in benzene. The solution enthalpies of 1-ethyl-3-methylimidazolium tricyanomethanide [EMIM][C(CN)₃], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF₄], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf₂] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO] in benzene were measured. The solvation enthalpies of imidazolium-based IL were calculated. Molar refractions of imidazolium-based IL form literature data on density and refractive indexes of IL were also calculated. The linear correlation between solvation enthalpy and molar refraction of IL was observed. This correlation can be used to calculate the vaporization enthalpy of imidazolium-based IL from solution calorimetry data.     

A metallacage encapsulating chloride as a probe for a solvation scale in ionic liquids

With the purpose of assessing the reactivity of chloride ions dissolved in ionic liquids (ILs), a relative scale for the solvation of chloride is given for a series of ILs based on the bis(trifluoromethane)sulfonimide ([Tf(2)N]) anion and different cations, 1-butyl-3-methylimidazolium ([bmim]), 1-butyl-2,3-dimethylimidazolium ([bdmim]), 1-butyl-1-methylpyrrolidinium ([bmpy]), 1-butylpyridinium ([bpy]), 1-pentyl-1,1,1-triethylammonium ([C(5)e(3)am]), and 1-(2-hydroxy)ethyl-3-methylimidazolium ([mimeOH]). Insights into the solvation of chloride are achieved by the thermodynamic study of the reaction of dissociation of a chloride-templated nickel(II) metallacage performed at various temperatures by UV-visible spectroscopy in each IL. The order of chloride solvation [C(5)e(3)am][Tf(2)N] < [bmpy][Tf(2)N] < [bmim][Tf(2)N] 相似文献   

Thermodynamic analysis for solubility of pimelic acid in ionic liquids

Based on the solubilities of pimelic acid in ionic liquids [EMIM][HSO₄], [PMIM]Br, [i-PMIM][HSO₄], [BMIM]Br, and [BMIM][HSO₄], dissolution enthalpy and dissolution entropy at different temperatures have been calculated. The experimental data of solubilities are correlated with the modified Apelblat equation. The thermodynamic properties of pimelic acid in ionic liquids were discussed. The solubilities correlated by the model are in good agreement with experimental data.     

Enzymatic ring‐opening polymerization of ε‐caprolactone by Yarrowia lipolytica lipase in ionic liquids

Yarrowia lipolytica (YLL), Candida rugosa (CRL), and porcine pancreatic lipase (PPL) were employed successfully as catalysts in the enzymatic ring‐opening polymerization (ROP) of ε‐caprolactone in the presence of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF₄]), 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF₄]), 1‐butylpyridinium tetrafluoroborate ([BuPy][BF₄]), 1‐butylpyridinium trifluoroacetate ([BuPy][CF₃COO]), 1‐ethyl‐3‐methylimidazolium nitrate ([EMIM][NO₃]) ionic liquids. Poly(ε‐caprolactone)s (PCLs) with molecular weights (M_n) in the range of 300–9000 Da were obtained. ¹H‐ and ¹³C‐NMR analyses on PCLs formed by YLL, CRL, and PPL showed asymmetric telechelic α‐hydroxy‐ω‐carboxylic acid end groups. Differences between CP‐MAS and MAS spectra are observed and discussed in terms of morphology. MALDI‐TOF spectra show the formation of at least seven species. Differential scanning calorimetry (DSC) and Wide Angle X‐Ray Scattering (WAXS) results demonstrate the high degree of crystallinity present in all the polyesters. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5792–5805, 2009     

Ideal gas solubilities and solubility selectivities in a binary mixture of room-temperature ionic liquids

This study focuses on the solubility behaviors of CO2, CH4, and N2 gases in binary mixtures of imidazolium-based room-temperature ionic liquids (RTILs) using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) at 40 degrees C and low pressures (approximately 1 atm). The mixtures tested were 0, 25, 50, 75, 90, 95, and 100 mol % [C2mim][BF4] in [C2mim][Tf2N]. Results show that regular solution theory (RST) can be used to describe the gas solubility and selectivity behaviors in RTIL mixtures using an average mixture solubility parameter or an average measured mixture molar volume. Interestingly, the solubility selectivity, defined as the ratio of gas mole fractions in the RTIL mixture, of CO2 with N2 or CH4 in pure [C2mim][BF4] can be enhanced by adding 5 mol % [C2mim][Tf2N].     

微波辅助合成有机膦功能化离子液体及对稀土离子的萃取

用微波辐射法,合成了5个含有机膦氧基团的离子液体：1-丙基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph2][Tf2N])、1-己基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph2][Tf2N])、1-丙基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph(OEt)][Tf2N])、1-己基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph(OEt)][Tf2N])和(3-苯基乙氧基氧膦基)丙基三乙胺双(三氟甲基磺酰基)亚胺盐([TENC3P(O)Ph(OEt)][Tf2N])。 用31P NMR、1H NMR、13C NMR、MS及FT-IR对产物结构进行了表征。 研究了这类离子液体对稀土Nd(III)的萃取性能。 结果表明,这类功能化离子液体可作为单一组分萃取稀土而无需加入有机稀释剂,离子液体结构对萃取效率影响很大,相同条件下季铵盐型结构的离子液体[TENC3P(O)Ph(OEt)][Tf2N]对稀土Nd(Ⅲ)的萃取效率最高。 稀土溶液pH值对萃取效率影响显著,近中性条件下(pH=6.63),对稀土Nd(Ⅲ)的萃取率最高。 用pH=1.00的盐酸溶液可以较好的从离子液体相反萃Nd(Ⅲ),反萃率可达94%。     

Hydrophobic ionic liquid‐based ultrasound‐assisted extraction of magnolol and honokiol from cortex Magnoliae officinalis

The hydrophobic ionic liquid of [BMIM][PF₆] was successfully used for the ultrasound‐assisted extraction of hydrophobic magnolol and honokiol from cortex Magnoliae officinalis. To obtain the best extraction efficiencies, some ultrasonic parameters including the concentration of [BMIM][PF₆], pH, ultrasonic power and ultrasonic time were evaluated. The results obtained indicated that the [BMIM][PF₆]‐based ultrasound‐assisted extraction efficiencies of magnolol and honokiol were greater than those of the [BMIM][BF₄]‐based ultrasound‐assisted extraction (from 48.6 to 45.9%) and the traditional ethanol reflux extraction (from 16.2 to 13.3%). Furthermore, the proposed extraction method is validated by the recovery, correlation coefficient (R²) and reproducibility (RSD, n=5), which were 90.8–102.6, 0.9992–0.9998, and 1.6–5.4%, respectively.     

Estimates of Internal Pressure and Molar Refraction of Imidazolium Based Ionic Liquids as a Function of Temperature

Estimates of the internal pressure (∂ U/∂ V) _T of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆], and 1-methyl-3-octylimidazolium tetrafluoroborate [OMIM][BF₄] were made from experimentally determined densities and speeds of sound in the temperature range 283.15 to 343.15 K. Values (∂ U/∂ V) _T for all the ILs studied are higher than those of water and molecular organic liquids. We also measured the refractive indices n _D in the temperature range 288.15 to 343.15 K and estimated the molar refraction R _M. Refractive indices of ILs were also higher than those of normal organic liquids but were comparable to those of long hydrocarbon chain organic solvents.     

Extraction of Metal Ions from Aqueous Solutions Using Imidazolium Based Ionic Liquids

This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag⁺ and Pb²⁺) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium, or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl}imide [EEIM][NTf₂], or [BEIM][NTf₂], or [HEIM][NTf₂], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF₆], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF₆] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] for comparison. The effect of anion type (NTf₂⁻ versus PF₆⁻) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous solution into the ILs. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users. Presented at the 236th ACS National Meeting, August 17–21, Philadelphia, USA.     

A Bloembergen–Purcell–Pound <Superscript>13</Superscript>C NMR relaxation study of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The molecular structure and rotational motion of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) were studied over a wide temperature range using the Bloembergen–Purcell–Pound ¹³C NMR spin–lattice relaxation method and NOE factors. Examination of the spin–lattice relaxation times (T ₁) and the rates (R ₁=1/T ₁) of the 1-butyl-3-methylimidazolium cation reveals the relative motions of each carbon in the imidazolium cation. The rotational characteristics of the [BMIM] cation are supported by ab-initio molecular structures of [BMIM][PF6] using density functional theory (DFT) and Hartree–Fock (HF) methods. The ab-initio gas phase structures of [BMIM][PF6] indicate that the 1-butyl-3-methylimidazolium C2 hydrogen, the ring methyl group, and the butyl side-chain hydrogen atoms form hydrogen bonds with the hexafluorophosphate anion.     

The effect of C2 substitution on melting point and liquid phase dynamics of imidazolium based-ionic liquids: insights from molecular dynamics simulations

Using molecular dynamics simulations, the melting points and liquid phase dynamic properties were studied for four alkyl-imidazolium-based ionic liquids, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate ([BMMIM][PF6]), 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), and 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate ([EMMIM][PF6]), respectively. Experimentally it has been observed that the substitution of a methyl group for a hydrogen at the C2 position of the cation ring leads to an increase in both the melting point and liquid phase viscosity, contrary to arguments that had been made regarding associations between the ions. The melting points of the four ionic liquids were accurately predicted using simulations, as were the trends in viscosity. The simulation results show that the origin of the effect is mainly entropic, although enthalpy also plays an important role.     

Liquid structures of 1-butyl-3-methylimidazolium tetrafluoroborate and carbon dioxide mixtures by X-ray diffraction measurements

X-ray diffraction measurements for the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF₄], mixed with CO₂ were carried out at high pressures using our developed polymer cell. The intermolecular distribution functions obtained for [BMIM][BF₄]–CO₂ mixtures showed that CO₂ molecules are preferentially solvated to the [BF₄]⁻ anion. The similar preferential solvation was previously observed in analogous 1-btuyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF₆], with a different anion, which is in harmony with the present results in [BMIM][BF₄]–CO₂.