Synthesis of aryl/alkyl(2,2′-bis-3-methylindolyl)methanes and aryl(3,3′-bis indolyl)methanes promoted by secondary amine based ionic liquids and microwave irradiation

Aryl/alkyl(2,2′-bis-3-methylindolyl)methanes and aryl(bis-3,3′-indolyl)methanes are synthesized in high yield using ionic liquids mediated by microwave. Reaction conditions and product recovery are simple and ionic liquids could be recycled.     

Influence of the ionic liquid structure on thiophene solubility

Binary liquid-liquid equilibria for 10 systems containing an ionic liquid with thiophene were measured by dynamic method in the temperature range from 283 K to the boiling point of thiophene. The influence of ionic liquid structure on solubility of thiophene is discussed in comparison with results taken from the literature. The solubility of thiophene in all investigated ionic liquids is high - below 0.31 ionic liquid mole fraction.     

Effect of polyethylene glycol (PEG-400) on the 1-butyl-3-methylimidazolium tetrafluoroborate-in-cyclohexane ionic liquid microemulsion

The effect of a common polymer, polyethylene glycol with molecular weight of 400 (PEG-400) on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄)/Triton X-100/cyclohexane ionic liquid (IL) reverse microemulsion has been investigated. The addition of PEG-400 leaded to the linear increase of the microemulsion droplet size, in accordance with the observation of dispersed phase, showing that PEG-400 was only solubilized into the polar interior of the IL microemulsions. FTIR spectroscopic analysis indicated that the addition of PEG-400 decreased the electrostatic interaction between the oxygen atoms of OE units and the positive electrical charged imidazolium cation of bmimBF₄. At the same time, the oxygen atoms of PEG-400 can also interact with the imidazolium cation. These results suggested that small amounts of PEG-400 entered the palisade layers of the IL microemulsion. The conductivity of the IL reverse microemulsions was decreased owing to the dilution of conducting polar cores by the addition of insulative PEG-400, indicating that PEG-400 was only solubilized into the reverse IL microemulsion interior. The conclusion was further supported by viscosity measurement.     

Biphasic asymmetric hydroformylation and hydrogenation by water-soluble rhodium and ruthenium complexes of sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl in ionic liquids

A biphasic catalytic system with water-soluble rhodium complexes of sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (labeled as (R)-BINAPS) in ionic liquid BMI·BF₄ has been developed for the asymmetric hydroformylation of vinyl acetate under mild conditions. The corresponding ruthenium complexes have been investigated for the biphasic asymmetric hydrogenation of dimethyl itaconate. The biphasic asymmetric hydroformylation of vinyl acetate provided 28.2% conversion and 55.2% enantiomeric excess when BMI·BF₄–toluene was used as the reaction medium at 333 K and 1.0 MPa for 24 h. The biphasic asymmetric hydrogenation of dimethyl itaconate in BMI·BF₄–ⁱPrOH at 333 K and 2.0 MPa afforded 65% enantiomeric excess with an activity similar to the homogenous analogs. Both biphasic catalytic systems with (R)-BINAPS ligand could be reused several times without significantly decrease in the activity, enantio- and regio-selectivities. The effects of properties of ionic liquid, molar ratio of ligand to rhodium, temperature, pressure and reaction time have been discussed.     

Use of selective ionic liquids and ionic liquid/salt mixtures as entrainer in a (vapor + liquid) system to separate n-heptane from toluene

During the last years, a large number of studies have evaluated the ability of ionic liquids (ILs) to separate aromatic from aliphatic hydrocarbons by liquid extraction. Nevertheless, in order to design a global process, a post-extraction step based on the aromatic recovery from the extract stream and the regeneration of the IL is required. Taking into account the negligible vapor pressure of the ILs, the use of separation units based on the difference of volatility among the components of the extract could be an appropriate way. However, that requires additional (vapor + liquid) equilibrium (VLE) data, which are scarce today. In this work, the isothermal VLE data for {n-heptane + toluene + 1-ethyl-3-methylimidazolium thiocyanate ([EMim][SCN])} and {n-heptane + toluene + 1-butyl-3-methylimidazolium thiocyanate ([BMim][SCN])} mixtures were experimentally measured at T = (323.2, 343.2 and 363.2) K over the whole composition range within the rich-IL miscibility region. For that, a static headspace gas chromatograph (HS-GC) was used. In addition, the non-random two liquids (NRTL) thermodynamic model was satisfactory applied to correlate the experimental VLE data.Finally, the effect of thiocyanate-based inorganic salts (AgSCN, Co(SCN)₂ and CuSCN) on the phase behavior of the above mentioned mixtures were also analyzed through the experimental determination of the isothermal VLE of the pseudo-ternary systems {n-heptane + toluene + [EMim][SCN]/salt mixture}.The obtained results show that the use of pure thiocyanate-based ILs as entrainer increases the n-heptane relative volatility from toluene whereas the addition of inorganic salts has not led to an improvement of these results.     

Effect of EMIMBF4 ionic liquid addition on the structure and ionic conductivity of LiBF4-complexed PVdF-HFP polymer electrolyte films

New polymer electrolyte films of lithium tetrafluoroborate (LiBF₄)-complexed poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) embedded with different quantities of 1-ethyl-3methylimidazolium tetrafluoroborate (EMIMBF₄) ionic liquid were prepared by solution casting. The prepared films were characterized using various techniques: X-ray diffraction, scanning electron microscopy, impedance spectroscopy and electrochemical measurements. The pure PVdF-HFP possessed a semi-crystalline structure and its amorphicity increased with the addition of LiBF₄ salt and EMIMBF₄ ionic liquid. The size and interconnection of pores in the films were enhanced by EMIMBF₄. Impedance measurements indicated that the room-temperature ionic conductivity of the films increased with increasing EMIMBF₄ concentration until 15 wt.%, being up to 0.202 × 10⁻⁴ S cm⁻¹, and then decreased with further increasing EMIMBF₄ concentration. In addition, the temperature-dependent ionic conductivity of the polymer electrolyte films followed an Arrhenius relation and the 15 wt.% EMIMBF₄-incorporated gel polymer electrolyte film exhibited a low activation energy for ionic conduction, being about 0.28 eV. Finally, the electrochemical stability window of the 85PVdF-HFP:15LiBF₄+15 EMIMBF₄ gel polymer electrolyte films was evaluated as approximately 4.4 V, which is a promising value for ion battery applications.     

Polymer electrolyte for lithium batteries based on photochemically crosslinked poly(ethylene oxide) and ionic liquid

Polymer/ionic liquid composites were investigated as solvent-free electrolytes for lithium batteries. Ternary electrolytes based upon poly(ethylene oxide), an ionic liquid and a conducting salt were UV crosslinked with benzophenone as the photoinitiator. Crosslinking leads to an increase in mechanical stability of the PEO composites. This straight-forward process provides a way to increase the content of ionic liquid and thus to raise ionic conductivity without loss of mechanical stability. Impedance measurements showed that the ionic conductivity of the composites is not affected by the UV curing process. Moreover, the UV curing process causes a decrease in the degree of crystallinity in the PEO composites which contributes to an increase in ionic conductivity. The present work is related to safety issues of lithium batteries.     

Effect of stationary phase polarity on the retention of ionic liquid cations in reversed phase liquid chromatography

Chromatographic analysis of ionic liquids on different types of packings offers interesting possibility to determine their retention mechanism. As a consequence, the major interactions between stationary phase ligands and analyzed chemical entities can be defined. The main aim of this work was to analyze cations of ionic liquids on chemically bonded stationary phases with specific structural properties. The attempt to predict the main interactions between positive ions of ionic liquids and stationary phase ligands was undertaken. For that purpose, butyl, octyl, octadecyl, phenyl, aryl, mixed, alkylamide, and cholesterolic packings were chosen and applied to the analysis of six most commonly used ionic liquids' cations. Obtained results indicate mainly dispersive and pi-pi type of interaction part in the retention mechanism of analyzed compounds.     

Study of the mesomorphic behaviour through the structure modification of azo and acetylene pyridinium and imidazolium-based ionic liquid crystals

ABSTRACT

In this work, 14 pyridinium and imidazolium-based ionic liquid crystal (ILC) with azo (N=N) and acetylene (C≡C) as linking group were synthesised in high yields and completely characterised. The structure of the molecules were planned in order to allow a complete investigation on how modifications such as presence and position of charges, linking group, number of alkoxy chains and their length affect the thermal stability and liquid crystalline behaviour. All compounds were thoroughly investigated using polarised optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements and thermogravimetric analysis (TGA). While the presence of charges favoured a liquid crystalline behaviour, especially SmA (and SmA₂) phase, a decrease of thermal stability was noticed. A strong dependence of the charge position and a preference for monolayer or bilayer molecular organisation was observed. On the other hand, it was demonstrated that the addition of a second alkoxy chain promoted layer distortions in some molecules, resulting in the formation of Smà and Cub phases. Also a direct comparison between the N=N and C≡C linking groups was realised, along with further comparison with literature data. The structure–properties are investigated in detail.     

Catalytic oxidation of cyclohexane with hydrogen peroxide and a tetracopper(II) complex in an ionic liquid

The catalytic peroxidative oxidation (with H₂O₂) of cyclohexane in an ionic liquid (IL) using the tetracopper(II) complex [(CuL)₂(μ₄-O,O′,O′′,O′′′-CDC)]₂·2H₂O [HL = 2-(2-pyridylmethyleneamino)benzenesulfonic acid, CDC = cyclohexane-1,4-dicarboxylate] as a catalyst is reported. Significant improvements on the catalytic performance, in terms of product yield (up to 36%), TON (up to 529), reaction time, selectivity towards cyclohexanone and easy recycling (negligible loss in activity after three consecutive runs), are observed using 1-butyl-3-methylimidazolium hexafluorophosphate as the chosen IL instead of a molecular organic solvent including the commonly used acetonitrile. The catalytic behaviors in the IL and in different molecular solvents are discussed.     

低温等离子体催化消除炭烟的研究进展

利用低温等离子体的非热力学平衡特性,在较低温度下将氧气分子转化为活性氧物种,从而将炭烟氧化消除,其炭烟消除速率和CO₂选择性等受等离子体放电结构、能量密度、反应气氛和催化剂的影响。本文对低温等离子体氧化消除炭烟的研究进展进行了总结,探讨反应器结构、能量密度、气相组成及催化剂对低温等离子体催化消除炭烟性能的影响规律,总结低温等离子体与催化剂协同催化机理的研究进展,分析低温等离子体与催化剂协同催化消除炭烟的主要挑战和发展趋势。     

Synthesis and application of ionic liquid matrices (ILMs) for effective pathogenic bacteria analysis in matrix assisted laser desorption/ionization (MALDI-MS)

Application of two new series of ionic liquid matrices (ILMs) based on the two most predominantly used conventional organic matrices (Sinapinic acid and 2,5-DHB) in conjugation with various bases (aniline (ANI), dimethyl aniline (DMANI), diethylamine (DEA), dicyclohexylamine (DCHA), pyridine (Pyr), 2-picoline(2-P), 3-picoline(3-P)) for bacterial analysis in matrix assisted laser desorption/ionisation mass spectrometry (MALDI-MS) are reported. The results reveal that ionic liquid matrices could significantly enhance the protein signals, reduce spot-to-spot variation and increase spot homogeneity. More importantly, these novel matrices would not produce any interference during MALDI-MS analysis. Among these ILMs, 2,5-DHB/ANI, 2,5-DHB/DMANI and 2,5-DHB/Pyr can be successfully applied to intact bacterial studies compared with other ILMs. Base molecules when added to conventional matrix can promote proton transfer between the bacterial lysate and the matrices. Due to the enhanced proton transfer efficiency by the ionic liquid matrices, almost all the biomolecules of the intact bacterial cells can be ionized and detected in the MALDI-MS. All synthesized ILMs were characterized using ESI (+)/MS and UV-spectroscopy.     

Effect of the polarity of silver nanoparticles induced by ionic liquids on facilitated transport for the separation of propylene/propane mixtures

The effect of ionic liquids on the formation of a partial positive charge on the surface of silver nanoparticle and its subsequent effect on facilitated olefin transport were investigated. Three different ionic liquids of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻), 1-butyl-3-methylimidazolium triflate (BMIM⁺Tf⁻), and 1-butyl-3-methylimidazolium nitrate (BMIM⁺NO₃⁻) were employed to control the positive charge density of the surface of silver nanoparticles. The positive charge density of the silver nanoparticles, as characterized by the binding energy of the silver atom, was in the following order: BMIM⁺BF₄⁻/Ag ? BMIM⁺Tf⁻/Ag > BMIM⁺NO₃⁻/Ag. This order was consistent with the tendency of ionic liquids to form free ions. The best separation performance for the propylene/propane mixtures was a mixed gas selectivity of 17 and a permeance of 7 GPU through a composite membrane consisting of BMIM⁺BF₄⁻/Ag. A better separation performance for olefin/paraffin mixtures was observed with a higher positive charge density of the silver nanoparticles. It was therefore concluded that facilitated olefin transport was a direct consequence of the surface positive charge of the silver nanoparticles induced by ionic liquids.     

A facile and highly efficient protocol for synthesis of poly(ether sulfone)s in ionic liquid/zwitterion

A benign approach for efficient preparation of poly(ether sulfone)(PES)(η_(inh) = 0.10-0.31 dL×g~(-1)) has been presented by using ionic liquid(IL)/zwitterion(ZI) as reaction medium. It has been found that the interaction between 4,4′-dihydroxydiphenylsulfone(Bisphenol-S) and ZI at elevated temperatures results in efficient reduction of dehydration time, which is confirmed by TGA curves, melting point of the mixture and FTIR spectra. Furthermore, no agglomeration is observed at dehydration stage, which is attributed to the high solubility of Bisphenol-S dipotassium salt in IL/ZI. This also makes the polymerization temperature(150 °C) much lower than a conventional method(220-300 °C). In order to demonstrate the efficiency of IL/ZI as reaction medium, the polymerization was also performed in sulfolane under the same reaction condition as that in IL/ZI.     

Polarographic behaviour of 2,2′-dipyridyl-2-pyridylhydrazone (DPPH) and pyridine-2-aldehyde-2-quinolylhydrazone (PAQH) at the dropping mercury electrode

The polarographic behaviour of 2,2-dipyridyl-2-pyridylhydrazone (DPPH) and pyridine-2-aldehyde-2-quinolylhydrazone (PAQH) atdme were studied in aqueousBritton-Robinson buffers containing 50% ethanol. The polarograms consist of one irreversible wave in the acidic and alkaline medium. Two electrons are consumed in the splitting of the N-N bond. The effect ofpH on the limiting current andE as well as the reduction mechanism are discussed and compared with similar compounds. The values of the kinetic parameters for the electrode reaction at differentpH values are also computed from the polarographic results.

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Das polarographische Verhalten von 2,2-Dipyridyl-2-pyridylhydrazon (DPPH) und Pyridin-2-aldehyd-2-chinolylhydrazon (PAQH) an der tropfenden Quecksilberelektrode

Zusammenfassung Das polarographische Verhalten der TitelverbindungenDPPH undPAQH wurde in wäßrigenBritton-Robinson-Puffern mit 50% Ethanolgehalt an der tropfenden Quecksilberlelektrode untersucht. Die Polarogramme zeigen eine irreversible Welle im basischen und alkalischen Medium. Zwei Elektronen werden bei der Spaltung der N-N-Bindung verbraucht. DerpH-Effekt auf den Grenzstrom undE _1/2 und auch auf den Reduktionsmechanismus wird diskutiert und mit ähnlichen Verbindungen verglichen. Die kinetischen Parameter für die Elektrodenreaktion werden für verschiedenepH-Werte aus den polarographischen Daten berechnet.

     

Effect of Ionic Strength on the Electrochemiluminescence Generation by Tris(2,2'-bipyridyl)ruthenium(II)/Tri-n-propylamine

Electrochemiluminescence(ECL) is a powerful transduction technique used in biosensing and in vitro diagnosis, while the mechanism of ECL generation is complicated and affected by various factors. Herein the effect of ionic strength on ECL generation by the classical tris(2,2'-bipyridyl)ruthenium(II)[Ru(bpy)₃²⁺]/tri-n-propylamine(TPrA) system was investigated. It is clear that the ECL intensity decreases significantly with the increase of ionic strength, most likely arising from the reduced deprotonation rate of TPrA^+·. We further combined microtube electrode(MTE) with ECL microscopy to unravel the evolution of ECL layer with the variation of ionic strength. At a low concentration of Ru(bpy)₃²⁺, the thickness of ECL layer(TEL) nearly kept unchanged with the ionic strength, indicating the surface-confined ECL generation is dominated by the oxidative-reduction route. While at a high concentration of Ru(bpy)₃²⁺, ECL generation is dominated by the catalytic route and TEL increases remarkably with the increase of ionic strength, because of the extended diffusion length of Ru(bpy)₃³⁺ at a reduced concentration of TPrA^·.     

Study on solid–liquid phase equilibria in ionic liquid: 1. The solubility of alkali chloride (MCl) in ionic liquid EMISE

This paper reports the solubility of alkali chloride MCl (M is Li, Na and K) in IL EMISE was measured in the temperature range of 293.15 K to 343.15 K. The relationship between solubility, m and temperature T may be expressed in an empiric formula: ln(m/m⁰) = A₁ + A₂T₀/T + A₃T/T⁰, where m⁰ is 1 mol/kg, T⁰ is 1 K. The observed sequence of solubility is LiCl > NaCl > KCl. The fact implies that the less the radius of alkali ion, the greater is its solubility because little ion is easy to get into the interstices of IL EMISE.     

Copper nanoparticles in an ionic liquid: an efficient catalyst for the synthesis of bis-(4-hydroxy-2-oxothiazolyl)methanes

Copper nanoparticles were synthesized and characterized by TEM, XRD and UV-vis techniques. The copper nanoparticles in an ionic liquid were employed as a recyclable catalyst for the synthesis of bis-(4-hydroxy-2-oxothiazolyl)methanes in excellent yields and in short reaction times.     

A novel glycosidation of glycosyl fluoride using a designed ionic liquid and its effect on the stereoselectivity

The glycosidations of glucopyranosyl fluoride and alcohols using an ionic liquid containing a protic acid effectively proceeded under mild conditions to afford the corresponding glycosides in good to high yields. The stereoselectivity of the glycosidation was significantly affected by the ionic liquid solvent. 1-n-Hexyl-3-methylimidazolium trifluoromethanesulfonate (C₆mim[OTf]), containing a trifluoromethanesulfonate anion, and 1-(3-cyanopropyl)-3-methylimidazolium trifluoromethanesulfonimidide (CNC₃mim[NTf₂]), possessing a cyano group at the side chain of the imidazolium cation, gave the β-stereoselectivity.     

Ionic liquid as a complexation and extraction medium combined with high-performance liquid chromatography in the evaluation of chromium(VI) and chromium(III) speciation in wastewater samples

A simple method has been proposed for the determination of chromium species by high-performance liquid chromatography (HPLC) after preconcentration by the ionic liquid, 1-butyl-3-methyimidazolium hexafluorophosphate ([C₄MIM][PF₆]). The simultaneous preconcentration of Cr(VI) and Cr(III) in wastewater was achieved with ammonium pyrrolidinedithiocarbamate (APDC) as the chelating agent and the ionic liquid [C₄MIM][PF₆] as the extractant. Baseline separation of the APDC chelates of Cr(III) and Cr(VI) was realised on a RP-C18 column using a mixture of methanol–acetonitrile–water (53:14:33, v/v) as the mobile phase at a flow rate of 1.0 mL min^{− 1}. The influences of several variables on the complexation and extraction were evaluated: pH, reaction time, APDC concentration and metal ion interference. Our results showed that when the linear concentration of Cr(VI) and Cr(III) ranged from 25 to 200 μg L^{− 1}, their linear correlation coefficients were between 0.9977 and 0.9978, their recoveries ranged from 91.8% to 95.8% and their relative standard deviations (n = 3) were between 0.31% and 1.8%. Common metal ions in water did not interfere with the determination. This method is a simple, fast, accurate, highly stable and selective method and has successfully been applied to the speciation of chromium in wastewater.