Atom transfer radical polymerization of styrenic ionic liquid monomers and carbon dioxide absorption of the polymerized ionic liquids

Polymeric forms of ionic liquids have many potential applications because of their high thermal stability and ionic nature. Two ionic liquid monomers, 1‐(4‐vinylbenzyl)‐3‐butyl imidazolium tetrafluoroborate (VBIT) and 1‐(4‐vinylbenzyl)‐3‐ butyl imidazolium hexafluorophosphate (VBIH), were synthesized through the quaternization of N‐butylimidazole with 4‐vinylbenzylchloride and a subsequent anion‐ exchange reaction with sodium tetrafluoroborate or potassium hexafluorophosphate. Copper‐mediated atom transfer radical polymerization was used to polymerize VBIT and VBIH. The effects of various initiator/catalyst systems, monomer concentrations, solvent polarities, and reaction temperatures on the polymerization were examined. The polymerization was well controlled and exhibited living characteristics when CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine or CuBr/2,2′‐bipyridine was used as the catalyst and ethyl 2‐bromoisobutyrate was used as the initiator. Characterizations by thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction showed that the resulting VBIT polymer, poly[1‐(4‐vinylbenzyl)‐3‐butyl imidazolium tetrafluoroborate] (PVBIT), was amorphous and had excellent thermal stability, with a glass‐transition temperature of 84 °C. The polymerized ionic liquids could absorb CO₂ as ionic liquids: PVBIT absorbed 0.30% (w/w) CO₂ at room temperature and 0.78 atm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1432–1443, 2005     

Comparison between polyethylenglycol and imidazolium ionic liquids as solvents for developing a homogeneous and reusable palladium catalytic system for the Suzuki and Sonogashira coupling

The carbapalladacycle complex of 4-hydroxyacetophenone oxime is a highly active palladium catalyst to effect the Suzuki coupling of aryl chlorides and other C-C forming reactions in water. In an attempt to develop a reusable, homogeneous system based on this complex, its stability against prolonged heating in different ionic liquids and polyethylenglycol (PEG) has been studied. It was found that the palladium complex decomposes in water, 1-butyl-1-methylimidazolium hexafluorophosphate and 1-butyl-1-methylimidazolium chloride to form palladium nanoparticles in the first two cases and PdCl₄²⁻ in the third case. In contrast, this cyclic palladium complex was stable upon extended heating in 1-butyl-2,3-dimethylimidazolium hexafluorophosphate and in PEG. The activity of this complex for the Suzuki and Sonogashira correlates with the stability of the complex, the activity in PEG being higher than any of the ionic liquids tested. Although the carbapalladacycle complex also decomposes in PEG upon reaction, the resulting Pd nanoparticles (2-5 nm size) are stabilized by PEG acting as ligand. In this way, a reusable, homogeneous system in PEG has been developed that is able to effect the Suzuki and Sonogashira couplings without the need of copper and phosphorous ligands, working at the open air.     

Nitrile-functionalized pyridinium ionic liquids: synthesis, characterization, and their application in carbon-carbon coupling reactions

A series of relatively low-cost ionic liquids, based on the N-butyronitrile pyridinium cation [C(3)CNpy](+), designed to improve catalyst retention, have been prepared and evaluated in Suzuki and Stille coupling reactions. Depending on the nature of the anion, these salts react with palladium chloride to form [C(3)CNpy](2)[PdCl(4)] when the anion is Cl(-) and complexes of the formula [PdCl(2)(C(3)CNpy)(2)][anion](2) when the anion is PF(6)(-), BF(4)(-), or N(SO(2)CF(3))(2)(-). The solid-state structures of [C(3)CNpy]Cl and [C(3)CNpy](2)[PdCl(4)] have been established by single-crystal X-ray diffraction. The catalytic activity of these palladium complexes following immobilization in both N-butylpyridinium and nitrile-functionalized ionic liquids has been evaluated in Suzuki and Stille coupling reactions. All of the palladium complexes show good catalytic activity, but recycling and reuse is considerably superior in the nitrile-functionalized ionic liquid. Inductive coupled plasma spectroscopy reveals that the presence of the coordinating nitrile moiety in the ionic liquid leads to a significant decrease in palladium leaching relative to simple N-alkylpyridinium ionic liquids. Palladium nanoparticles have been identified as the active catalyst in the Stille reaction and were characterized using transmission electron microscopy.     

以N为中心的阴离子离子液体的合成、表征及应用

首次通过不同阴离子的钾盐和不同的季铵化的咪唑,吡咯溴盐/氯盐进行离子交换,合成了一系列含氰基官能团的阴离子功能化离子液体。通过红外、核磁共振、质谱对离子液体的结构进行表征;通过TGA对离子液体的热稳定性进行测定,结果发现功能化离子液体具有良好的热稳定性,其分解温度在224-289℃范围内。将功能化离子液体[EMIm][N(CN)COC2H5]作为配体应用于无膦配体的Suzuki偶联反应,发现在反应中加入功能化离子液体[EMIm][N(CN)COC2H5]可以使反应收率提高10-20%。     

Hydroxyl-containing imidazolium ionic liquids

A number of imidazolium ionic liquids with bis(trifluoromethylsulfonyl)imide anion containing a ω-hydroxyalkyl substituent of different lengths in the cation (n_С = 2–8) were synthesized. The properties of the obtained liquids were investigated by DSC, TGA, IR, and NMR spectroscopy. Their thermal stability was studied; melting points, viscosity, and volatility in vacuum were measured. The possibility of using synthesized ionic liquids as heat carriers under high vacuum conditions is demonstrated.     

离子液体对H2O2氧化环己烯制备反-1,2-环己二醇的催化作用

以H2O2为氧化剂,研究了离子液体为催化剂和溶剂,环己烯氧化生成反-1,2-环己二醇的反应。 考察了不同咪唑型离子液体、反应时间、反应温度和H2O2用量等对产率和选择性的影响, 实验结果表明,在7种咪唑型离子液体催化体系中,阳离子为咪唑环上含有1或2个羧基,阴离子为[PF6]的离子液体催化效果较好。 反应温度为100 ℃,n(H2O2)∶n(Cyclohexene)＝1.1∶1,反应5 h时,离子液体c（0.60 g,2.1 mmol）催化生成的反-1,2-环己二醇的产率和选择性分别为95%和97%,而离子液体f（0.20 g,0.6 mmol）催化生成的反-1,2-环己二醇的产率和选择性分别为84%和90%,从离子液体的用量来看,含2个羧基的离子液体f的催化效率更高。     

Highly efficient synthesis of dicoumarols and xanthene derivatives in presence of Brønsted–Lewis acidic ionic liquids catalyst

A series of metal chloride-based acidic ionic liquids have been prepared and used as an efficient catalyst in one-pot multicomponent synthesis of biscoumarins and substituted xanthenes derivatives under solvent-free conditions. Among the acidic ionic liquids, N-methylpyrrolidonium zinc chloride (Hnmp/ZnCl₃)-based Brønsted–Lewis acidic ionic liquids were found to be an effective and recyclable catalyst for a one-pot synthesis of biscoumarins through the domino Knoevenagel–Michael reaction of a variety of aldehydes with 4-hydroxycoumarin in short reaction times. The reactions which occur under relatively mild conditions afforded the biscoumarin derivatives employing a very low loading of catalyst in satisfactory isolated yields and high purity after simple work-up. The Brønsted–Lewis acidic ionic liquid catalyst was reused four times without any variation in yield.     

Fe3O4@SiO2-polymer-imid-Pd magnetic porous nanosphere as magnetically separable catalyst for Mizoroki–Heck and Suzuki–Miyaura coupling reactions

The activity of palladium nanoparticles supported on poly (N-vinylpyrrolidone) grafted Fe₃O₄@SiO₂ was investigated in the cross-coupling reactions. We have applied this catalyst under low loading of the supported palladium nanoparticles for the coupling of aryl halides with alkenes (Mizoroki–Heck reaction) and organoboronic acids (Suzuki–Miyaura reaction) in the absence of phosphorous ligands. Short reaction times and excellent yields of the products express the effectiveness of this catalyst. The nanocatalyst can be separated from the reaction mixture by applying a permanent magnet externally and can be reused for six times without appreciable change in catalytic activity. Also, the amount of leaching of Pd nanoparticles has been determined by ICP analysis and results showed low leaching of the metal into solution from the supported catalyst.     

Adhesion of small particles of palladium on Al2O3

The adhesion of small particles of palladium prepared by thermal evaporation onto a substrate of Al₂O₃ was studied. Al₂O₃ was obtained by oxidation of a pollycristalline aluminum strip. The deposit of palladium was observed by Transmission Electron Microscopy which allowed to determine the size and the density of particles according to the average deposition thickness. The adhesion of particles was determined by two methods: the study of particle number density, and the study of the particle shapes.     

Efficient synthesis of 1-carbamatoalkyl-2-naphthols using Brønsted acidic ionic liquid as reusable catalyst

Efficient synthesis of 1-carbamatoalkyl-2-naphthols can be carried out in the presence of halogen-free Brønsted acidic ionic liquid, synthesized from 1,4-diaza-bicyclo[2.2.2]octane (DABCO) and 1,4-butanesulfonate. A wide range of aldehydes and carbamates easily undergo condensation with 2-naphthol to afford the desired products in good to excellent yields. The present methodology offers several advantages, such as a simple work-up procedure and short reaction times. The catalyst can be recycled and reused without substantial reduction in catalytic activities.     

Inclusion Complexes of Ionic Liquids and Cyclodextrins: Are They Formed in the Gas Phase?

The interaction of imidazolium-based ionic liquids with α- and β-cyclodextrins was investigated by electrospray ionization mass spectrometry with variable collision induced dissociation energy and quantum chemical gas-phase calculations. The center-of-mass energy at which 50 % of a precursor ion decomposes (E_cm,1/2) was determined for the isolated [cyclodextrin + cation]⁺ or [cyclodextrin + anion]^– adduct ions of imidazolium-based ionic liquids with different alkyl chain lengths combined with a large set of anions, such as chloride, bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, dicyanamide, and hydrogensulfate. Moreover, both symmetric and asymmetric imidazolium cationic cores were evaluated. The relative interaction energies in the adduct ions were interpreted in terms of the influence of cation/anion structures and their inherent properties, such as hydrophobicity and hydrogen bond accepting ability, in the complexation process with the cyclodextrins. The trends observed in the mass spectral data together with quantum-chemical calculations suggest that in the gas phase, cations and anions will preferentially interact with the lower or upper rim of the cyclodextrin, respectively, as opposed to what has been reported in condensed phase where the formation of an inclusion complex between ionic liquid and cyclodextrin is assumed.

The effect of synthesis method and post-synthesis treatment on the formation of neutral Mn(II) complex into anionic zeolite structure and investigation of its catalytic activity in the epoxidation of alkenes

In this study, we improved the catalytic performance of manganese porphyrin encapsulated HY zeolite for alkene epoxidation reaction. For this purpose, Manganese tetra pyridyl porphyrin encapsulated into modified dealuminated Y zeolite (MnTPP-MDAZY) was synthesized using zeolite template synthesis method. This heterogenized catalyst was characterized by FT-IR, UV–Vis, XRD and atomic absorption spectra (AAS) technique. Catalyst loading was 0.263 mmol/g support. In this way, high catalyst loading is probably related to the decrease of the size of metalloporphyrin and the post-synthesis treatment. The latter one causes the increase of the diameter of the mesoporous structure as a result of the dealumination of zeolite with EDTA treatment. High catalyst loading efficiently enhances the epoxidation of alkenes.     

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.     

A highly efficient, recyclable catalyst for C-C coupling reactions in ionic liquids: pyrazolyl-functionalized N-heterocyclic carbene complex of palladium(II)

[reaction: see text] A hemilabile pyrazolyl-functionalized N-heterocyclic carbene complex of palladium(II) has been synthesized. It is an excellent catalyst for Heck and Suzuki cross-coupling reactions in ionic liquids.     

新型1,3-二丁基咪唑离子液体中脂肪酶催化折分(R,S)-1-苯乙醇

设计合成6种采用不同1,3-二丁基咪唑阳离子和六氟磷酸(PF6-)或双三氟甲烷磺酰亚胺(TFSI-)阴离子的离子液体.以脂肪酶催化拆分1-苯乙醇为模型反应,分别考察介质、水含量和温度对反应的影响.结果表明,在1,3-二异丁基咪唑六氟磷酸盐([D(i-C4)Im][PF6])离子液体介质中酶的活性和反应性明显高于其它离子液体和正己烷.因此,[D(i-C4)Im][PF6]被确定为反应介质.在最佳条件下,初始反应速率是1.93μmol?mg-1?min-1,1-苯乙醇的转化率达50%,对映体过量值eep99%,酶的半衰期为348h,酶重复使用10次后活性没有明显减少.此外,圆二色谱、内源荧光光谱和光学显微镜研究表明,酶在[D(i-C4)Im][PF6]中保温6d后氨基酸残基的裸露程度略有增加,但其二级结构仍保持稳定,且以天然的折叠球形态存在.     

Why Is CO2 so soluble in imidazolium-based ionic liquids?

Experimental and molecular modeling studies are conducted to investigate the underlying mechanisms for the high solubility of CO2 in imidazolium-based ionic liquids. CO2 absorption isotherms at 10, 25, and 50 degrees C are reported for six different ionic liquids formed by pairing three different anions with two cations that differ only in the nature of the "acidic" site at the 2-position on the imidazolium ring. Molecular dynamics simulations of these two cations paired with hexafluorophosphate in the pure state and mixed with CO2 are also described. Both the experimental and the simulation results indicate that the anion has the greatest impact on the solubility of CO2. Experimentally, it is found that the bis(trifluoromethylsulfonyl)imide anion has the greatest affinity for CO2, while there is little difference in CO2 solubility between ionic liquids having the tetrafluoroborate or hexafluorophosphate anion. The simulations show strong organization of CO2 about hexafluorophosphate anions, but only small differences in CO2 structure about the different cations. This is consistent with the experimental finding that, for a given anion, there are only small differences in CO2 solubility for the two cations. Computed and measured densities, partial molar volumes, and thermal expansion coefficients are also reported.     

Hydrodehalogenation of Halogenated Organic Contaminants from Aqueous Sources by Pd Nanoparticles Dispersed in the Micropores of Pillared Clays Under Transfer Hydrogenation Condition

Palladium nanoparticles dispersed in the micropores of the Al-pillared clay was prepared by chemical reduction of palladium chloride salt. The Al-pillared clay was prepared by insertion of [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ clusters into clay interlayer and subsequent thermal activation. The pillared clay supported system (Pd/Al–P) was characterized using XRD, IR, UV–Vis, SEM, TEM and sorptometric technique. The expansion of the interlayer space as a result of pillaring was noted for Pd/Al–P system from the XRD study. The TEM study of the supported system indicated well dispersion of the Pd species with particle size in the range of 5–30 nm. The supported Pd particles were used as an efficient heterogeneous catalyst for the hydrodehalogenation of halogenated organics under hydrogen transfer condition using hydrazine hydrate as hydrogen donating agent. The effect of various reaction parameters such as temperature, time, and nature of support, type of hydrogen transfer agents and functionality of substrate was studied in details. The catalytic study clearly indicated superior catalytic activity of the supported Pd system in presence of hydrazine hydrate as hydrogen donating agent. The Al-pillared clay as support influences the dispersion and catalytic activity of the supported Pd nanoparticles.     

Preparation and characterization of cationic pH-sensitive SiO2/polymer core-shell nanoparticles with amino groups in the shell

Silica/poly(styrene-N,N′-dimethylaminoethyl methacrylate) (SiO₂/P(St-DMAEMA)) cationic pH-responsive core-shell particles with a narrow size distribution and diameter of less than 200 nm were synthesized by emulsion polymerization. The effects of the St/DMAEMA molar ratio, SiO₂ core size, monomer amount, and cross-linking degree on the morphology and pH-responsiveness of the core-shell particles were investigated by transmission electron microscopy, dynamic light scattering, and conductometric titration. The results showed that core-shell particles with only one SiO₂ core could be obtained when the cross-linker divinyl benzene (DVB) was used, and the diameter of the core-shell particles increased with the size of the SiO₂ core and the total amount of monomer. It was observed that the amount of surface amino groups, zeta potential, and volume swelling ratio of the core-shell particles were significantly affected by the St/DMAEMA molar ratio, and a high volume swelling ratio was achieved at pH 4 and a DVB content of 3 mol%. The zeta potential was observed to be a function of pH, and the particles were positively charged when the pH value was below approximately 7.2.     

The role of Pd nanoparticles in ionic liquid in the Heck reaction

Pd(0) nanoparticles with approximately 2 nm diameter, immobilized in 1-n-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, are efficient catalyst precursors for coupling of aryl halides with n-butylacrylate. In situ TEM analysis of the ionic liquid catalytic solution after the catalytic reaction shows the formation of larger nanoparticles ( approximately 6 nm). The palladium content in the organic phase during the arylation reaction was checked by ICP-AS and shows significant metal leaching (up 34%) from the ionic phase to the organic phase at low substrate conversions and drops to 5-8% leaching at higher conversions. These results strongly suggest that the Pd(0) nanoparticles serve as a reservoir of "homogeneous" catalytic active species.