Use of ionic liquids in the synthesis of nanocrystals and nanorods of semiconducting metal chalcogenides

We have synthesized nanoparticles of hexagonal CdS in the diameter range 3-13 nm by the reaction of cadmium acetate dihydrate with thioacetamide in imidazolium [BMIM]-based ionic liquids. We have obtained three different particle sizes of CdS by changing the anion of the ionic liquid. Addition of trioctylphosphine oxide (TOPO) to the reaction mixture causes greater monodispersity as well as smaller particle size, while addition of ethylenediamine produces nanorods of 7 nm average diameter. Hexagonal ZnS and cubic PbS nanoparticles with average diameters of 3 and 10 nm, respectively, have been prepared by the reaction of the metal acetates with thioacetamide in [BMIM][BF4]. Hexagonal CdSe nanoparticles with an average diameter 12 nm were obtained by the reaction of cadmium acetate dihydrate with dimethylselenourea in [BMIM][BF4]. In this case also we observe the same effect of the addition of TOPO as in the case of CdS. Addition of ethylenediamine to the reaction mixture gives rise to nanorods. ZnSe nanowires with a cubic structures, possible diameters in the range 70-100 nm by the reaction of zinc acetate dihydrate with dimethylselenourea in [BMIM][MeSO4]. The nanostructures obtained are single crystalline in all the cases. Most of the nanostructures show characteristic UV/Vis absorption and photoluminescence emission spectra. The thermodynamically most stable structures are generally produced in the synthesis carried out in ionic liquids.     

Microwave-assisted synthesis of sulfide M2S3 (m = Bi, Sb) nanorods using an ionic liquid

Single-crystalline Bi(2)S(3) and Sb(2)S(3) nanorods have been successfully synthesized by the microwave-assisted ionic liquid method. The starting reagents were Bi(2)O(3) or Sb(2)O(3), HCl, Na(2)S(2)O(3), and ethylene glycol (EG) or ethanolamine, and the ionic liquid used was 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF(4)]). Our experiments showed that the ionic liquid played an important role in the morphology of M(2)S(3) (M = Bi, Sb). Single-crystalline Bi(2)S(3) nanorods could be prepared in the presence of [BMIM][BF(4)]. However, urchinlike Bi(2)S(3) structures consisting of nanorods were formed without using [BMIM][BF(4)]. Single-crystalline Sb(2)S(3) nanorods were obtained in the presence of [BMIM][BF(4)]. However, single-crystalline Sb(2)S(3) nanosheets could be prepared in the absence of [BMIM][BF(4)]. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction (ED).     

Halo- and azidodediazoniation of arenediazonium tetrafluoroborates with trimethylsilyl halides and trimethylsilyl azide and sandmeyer-type bromodediazoniation with Cu(I)Br in [BMIM][PF6] ionic liquid

Reaction of [ArN(2)][BF(4)] salts immobilized in [BMIM][PF(6)] ionic liquid (IL) with TMSX (X = I, Br) and TMSN(3) represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH(2) by in situ diazotization with [NO][BF(4)] followed by reaction with TMSX or TMSN(3). Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN(3) and with TMSI generally gave the highest chemoselectivity toward ArN(3) and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN(2)][BF(4)]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF(6)]/TMSX/[ArN(2)][BF(4)] indicated that TMSF is formed primarily via [ArN(2)][BF(4)]/TMSX, generating [ArN(2)][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN(2)][BF(4)] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation.     

Structures of ionic liquids with different anions studied by infrared vibration spectroscopy

We investigated the structures of ionic liquids (1-butyl-3-methylimidazolium iodide [BMIM][I] and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]) and their aqueous mixtures using attenuated total reflection (ATR) infrared absorption and Raman spectroscopy. The ATR spectrum in the CHx (x = 1, 2, 3) vibration region from 2800 to 3200 cm-1 was very different between [BMIM][BF4] and [BMIM][I] even though all the spectral features in this region were from the butyl chain and the imidazolium ring of the same cation. The spectrum did not change appreciably irrespective of the water concentration for [BMIM][BF4], whereas the spectrum from [BMIM][I] showed significant changes as the water concentration was increased, especially in CH-vibration modes from the imidazolium ring. For very diluted solutions both aqueous mixtures of [BMIM][I] and [BMIM][BF4] showed very similar spectra. Mixing of [BMIM][I] with heavy water (D2O) facilitated the isotopic exchange of the proton attached to the most acidic carbon of the imidazolium ring into deuterium from D2O, whereas even prolonged exposure to D2O did not induce any isotopic exchange for [BMIM][BF4]. Raman spectra around 600 cm(-1) indicative of the butyl chain conformation also changed differently as the water concentration was increased between [BMIM][I] and [BMIM][BF4]. These differences are considered to come from the variation in the position of the anion, where I- is expected to be closer to the C(2) hydrogen of the imidazolium cation and interacting more specifically as compared to BF(4-).     

离子液体体系中离子型锰卟啉对苯乙烯的催化氧化

以单氧给体乙酰碘苯[PhI(OAc)2]为氧源, 在无需轴向配体和有机溶剂的参与下, 离子型锰卟啉[MnⅢ(BF4)T(N-Me-4-Py)P][BF4]4和离子液体 [BMIM]BF4组成的多元离子液体体系, 在温和的反应条件下对苯乙烯的催化氧化表现出较高的活性(87%)和环氧苯乙烷选择性(90％), 并且有较好的底物普适性. 构筑的锰卟啉多元离子液体体系可以一定程度上抑制卟啉聚合和氧化降解等反应.     

Dynamically coated silica monolith with ionic liquids for capillary electrochromatography

An ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) was introduced as dynamic coating of a silica monolithic column for capillary electrochromatography of phenols and nucleoside monophosphates. The run-to-run and column-to-column repeatability of migration time for six phenols were satisfactory on this column with relative standard deviation values less than 0.90 and 4.31%, respectively. Anodic electroosmotic flow (EOF) was observed, which increased with the increase of [BMIM][BF4] concentration within 120 mM and when [BMIM][BF4] concentration was above 120 mM, EOF leveled off due to the saturation of [BMIM][BF4] on the monolith. Efficient separation of phenols and nucleoside monophosphates on this dynamically coated monolithic column was obtained, compared with a dynamically coated fused-silica column and unmodified silica monolithic column. The retention behavior of uncharged phenols is mainly manipulated by hydrophobic interactions due to the presence of butyl groups, and that of nucleoside monophosphates is governed by the electrostatic attraction mechanism based on the interaction between positively charged [BMIM][BF4] moieties and negatively charged phosphate groups. In addition, silica matrix also contributes to the separation resolution.     

基于金属介导和离子液体的新型绿原酸印迹整体柱的制备及评价

选用1-乙烯基-3-乙基咪唑四氟硼酸盐([VElm]BF4,一种离子液体)作为功能单体,以Co2+为介导离子,结合1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF4)/二甲基亚砜(DMSO)二元致孔体系制备了绿原酸印迹整体柱。经过对制备参数的考察,确定最佳比例为绿原酸:Co2+:[VElm]BF4:EDMA(乙二醇二甲基丙烯酸酯)(摩尔比)=1:1:5:20,[BMIM]BF4:DMSO=3:1(V/V),最大印迹因子达2.10。通过优化色谱条件,最终在乙腈:20 mmol/L乙酸钠缓冲液(pH 4.2)=70:30(V/V)时实现了绿原酸及其类似物的完全分离。由此可见,以离子液体为功能单体及致孔剂,在金属介导策略下制备的分子印迹聚合物可实现绿原酸的特异性识别及分离。     

Synthesis of cyano-bridged magnetic nanoparticles using room-temperature ionic liquids

A principally new exploit of ionic liquids as an alternative reaction medium in the synthesis of cyano-bridged coordination-polymer nanoparticles is reported. Stable colloid solutions containing nanoparticles of cyano-bridged molecule-based magnets, M)[Fe(CN)6]2/[RMIM][BF4] (M2+=Ni, Cu, Co) and Fe4[Fe(CN)6]3/[RMIM][BF4] (R=1-butyl (BMIM), 1-decyl (DMIM)), were prepared in the corresponding 1-R-3-methylimidazolium tetrafluoroborate [RMIM][BF4], which acts as both a stabilising agent and a solvent. By varying the length of the N-alkyl chain on the imidazolium cation of [RMIM]+ and the temperature, the growing process can be controlled to produce nanoparticles of different sizes. By studying the magnetic properties of frozen colloids it is shown that the relaxation of magnetisation is strongly influenced by interparticle interactions, which leads to the appearance of spin-glass-like dynamics in these systems.     

Shape-controlled synthesis of manganese oxide octahedral molecular sieve three-dimensional nanostructures

Cryptomelane-type manganese oxide octahedral molecular (OMS) sieve three-dimensional (3D) nanostructures were synthesized via facile temple-free low-temperature hydrothermal reactions. Morphologies of the cryptomelane-type OMS-2 nanoparticles with tunnel dimension of 4.6 x 4.6 A can be tuned by varying reaction temperatures. At low temperature (120 degrees C), OMS-2 dendritic nanoclusters composed of uniform single-crystal nanotetragonal prisms with square cross-sections were formed. At high temperature (180 degrees C), the morphologies of OMS-2 became spherical dandelion-like microspheres composed of uniform single-crystal OMS-2 nanoneedles. Slow oxidation of Mn(2+) by Cr(2)O(7)(-) under hydrothermal conditions is critical for the formation of the hierarchically ordered OMS-2 3D nanostructures.     

Enhanced refolding of lysozyme with imidazolium-based room temperature ionic liquids: Effect of hydrophobicity and sulfur residue

The expression of recombinant proteins in microorganism frequently leads to the formation of insoluble aggregates, inclusion bodies (IBs). Thus, the additional in vitro protein refolding process is required to convert inactive IBs into water-soluble active proteins. This study investigated the effect of sulfur residue and hydrophobicity of imidazolium-based room temperature ionic liquids (RTILs) on the refolding of lysozyme as a model protein in the batch dilution method which is the most commonly used refolding method. When lysozyme was refolded in the refolding buffer containing [BF4]-based RTILs with a systematic variety of alkyl chain on cations varying from two to eight, less hydrophobic imidazolium cations having shorter alkyl chains were effective to facilitate lysozyme refolding. Compared to the conventional refolding buffer, 2 times higher lysozyme refolding yield was obtained in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) containing refolding buffer. The refolding yield of lysozyme was even more increased by 2.5 times when 1-butyl-3-methylimidazolium methylsulfate ([BMIM][MS]) containing sulfur residue on anion was used. The sulfur residue in [BMIM][MS] is supposed to improve the refolding yield of lysozyme which has 4 intramolecular disulfide bonds. For dilution-based refolding of lysozyme, the optimum concentrations of RTILs in refolding buffer were found to be 1.0 M [EMIM][BF4] and 0.5 M [BMIM][MS], respectively. The optimum temperate for dilution-based refolding of lysozyme with RTILs was 4 °C.     

Ionic liquid buffers: a new class of chemicals with potential for controlling pH in non-aqueous media

Ionic liquids with buffering characteristics, synthesized by the reaction of [RMIM]OH base moieties with phthalic and tartaric acid, respectively, are potential reagents for controlling pH in non-aqueous media; remarkable [Base]/[Acid] molar ratio dependence of the catalytic activities has been observed in the hydrogenation of olefins with [RuCl2(PPh3)3] complex in DMF and [BMIM][BF4].     

Salen Mn（Ⅲ）配合物的合成及其在离子液体中对苯乙烯环氧化反应的催化性能

合成了在5,5’位上分别含羟基叔胺基和酯基叔胺基取代基的新型手性水杨醛Schiff碱的Salen Mn（Ⅲ）配合物1～4．在CH2Cl2／H2O反应体系中,以吡啶氮氧化物（PyNO）为助催化剂,NaCl0为氧化剂,考察了配合物1—4对苯乙烯环氧化的催化性能．以氯化-双[3-（叔丁基）-5-（N,N-二（乙醇基）氨基亚甲基）水杨醛]缩（1r,2R）-二苯基乙二胺[N,N’,O,O’]锰（Ⅲ）2和氯化-双[3-（叔丁基）-5-（N,N-二（乙酰乙酯基）氨基亚甲基）水杨醛]缩（1R,2R）-二苯基乙二胺[N,N’,O,O’]锰（11I）4为例,研究了不同的离子液体[BMIM]PF6和[BMIM]BF4对苯乙烯环氧化反应的影响．结果显示,两种离子液体的加入均能使催化剂循环使用,在离子液体[BMIM]PF。中,配合物2和4催化得到的环氧化物ee％值分别为53．2％和55．8％,且催化剂可以重复使用四次,效果好于在离子液体[BMIM]BF4中对苯乙烯的催化的影响．     

Determination of an acidic scale in room temperature ionic liquids

The acidity scale of different Br?nsted acids in ionic liquids such as [BMIM][NTf2], [BMIM][BF4], and [BMMIM][BF4] has been investigated by determination of Hammett functions, using a spectrophotometric indicator method. This scale should permit one to correlate the acidity strength of ionic liquid systems with their ability to achieve acid-catalyzed reactions.     

Can the absence of solvation of neutral reagents by ionic liquids be responsible for the high reactivity in base-assisted intramolecular nucleophilic substitutions in these solvents?

[reaction: see text] The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1a) into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (2a) induced by amines have been studied in two room-temperature ionic liquids (IL-1, [BMIM][BF4] and IL-2, [BMIM][PF6]). The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents previously studied (both polar or apolar, protic or aprotic). Presumably, this could depend on their peculiar ability to minimize the strong substrate-solvent, amine-solvent and amine-amine interactions occurring in conventional solvents.     

Rapid synthesis of flower-like Cu2O architectures in ionic liquids by the assistance of microwave irradiation with high photochemical activity

A novel and facile protocol for the rapid synthesis of flower-like Cu(2)O architectures is reported in the presence of ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM]BF(4)) with the assistance of microwave irradiation. The hierarchical structures are assembled from many thin nanosheets with tunable sizes by adjusting the amount of [BMIM]BF(4) in the reaction solution. Noticeably, the flower-like Cu(2)O architectures present a high surface area of 65.77 cm(2) g(-1) with a band gap of about 2.25 eV, and exhibit high and stable photochemical activity for the reduction of Cr(VI) to Cr(III) under visible light irradiation. A reasonable model of an absorption and diffusion-limited aggregation process is proposed for explaining the possible formation mechanism of the flower-like Cu(2)O. The approach described in this study provides a feasible and rapid method to synthesize flower-like Cu(2)O with a hierarchical structure that is ready for application in the fields of photocatalytic hazard pollutants.     

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.     

Electrophilic chemistry of propargylic alcohols in imidazolium ionic liquids: propargylation of arenes and synthesis of propargylic ethers catalyzed by metallic triflates [Bi(OTf)3, Sc(OTf)3, Yb(OTf)3], TfOH, or B(C6F5)3

Metallic triflates M(OTf)(3) (M = Bi, Sc, Yb), immobilized in imidazolium ionic liquids [BMIM][BF(4)], [BMIM][PF(6)] and [BMIM][OTf] are efficient systems for one-pot reactions of propargylic alcohols 1,3-diphenyl-2-propyn-1-ol Ia, 1-methyl-3-phenyl-2-propyn-1-ol Ib, and 2-pentyn-1-ol Ic, with a wide range of arenes bearing activating substituents, under mild conditions. The [BMIM][PF(6)]/B(C(6)F(5))(3) and [BMIM][PF(6)]/TfOH systems were superior in propargylation with Ib and Ic, while reaction of 3-phenyl-2-propyn-1-ol Id with activated aromatics resulted in the formation of diaryl-propanones instead. Propargylation of anisole with Ib under M(OTf)(3) catalysis is highly para selective, but with TfOH or B(C(6)F(5))(3) as catalyst the ortho isomer was also formed. Steric influence of the propargylic moiety on substrate selectivity is reflected in the lack of ortho propargylation for phenol and ethylbenzene by using propargylic alcohol Ia, and notable formation of the ortho isomer employing alcohol Ib. In the later case para selectivity could be increased by running the reaction at r. t. for 10 h. The Bi(OTf)(3)-catalyzed reaction of 1,3-dimethoxybenzene with Ia led to minor formation of dipropargylated derivative, along with the monopropargyl product. Propargylation of the less reactive arenes (mesitylene, ethylbenzene, toluene), using Sc(OTf)(3) as catalyst, led increasingly to the formation of dipropargylic ethers and propargyl ketones, with no ring propargylation product with toluene. Concomitant formation of dipropargylic ether was also observed in Yb(OTf)(3)-catalyzed propargylation of β-naphthol, whereas propargylation of 2-nitro and 4-nitro-aniline led to N-propargylation. The recycling/reuse of the IL was demonstrated in representative cases with no appreciable decrease in the conversions over 3 cycles. It was also shown that recycled IL could be used to propargylate a different aromatic compound. The efficacy of IL/M(OTf)(3) and IL/TfOH systems for cross-breeding two propargylic alcohols or a propargylic alcohol with a non-propargylic alcohol and/or self-coupling, to form a wide variety of functionalized ethers is also demonstrated.     

锰八面体分子筛的合成、表征及其对二甲醚燃烧的催化性能

以高锰酸钾和马来酸为原料,以聚乙二醇单甲醚(MPEG)为模板剂,采用溶胶凝胶法合成了锰八面体分子筛(OMS-2),并将其用于二甲醚的催化燃烧反应.XRD,FT-IR和UV-Vis结果表明,合成的材料为隐钾锰矿型的锰氧化物.TEM结果表明合成的材料具有棒状的外形结构,其中MPEG起模板导向剂的作用.O2-TPD和H2-TPR结果表明合成的OMS-2材料容易还原,富有晶格氧.OMS-2材料在二甲醚催化燃烧中表现出优异的催化性能,能够在较低的温度下将二甲醚完全转化为CO2和H2O,晶格氧在该反应中起非常重要的作用.     

Lipase-catalyzed glucose fatty acid ester synthesis in ionic liquids

[reaction: see text] Glucose fatty acid ester synthesis with poly(ethylene glycol)-modified Candida antarctica lipase B (CAL-B) was performed in pure 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF(4)] (30% conversion) and in pure 1-butyl-3-methyl imidazolium hexafluorophosphate [BMIM][PF(6)] (35% conversion). In a solvent system composed of ionic liquid and 40% t-BuOH conversions up to 90% and isolated yields of up to 89% were achieved using fatty acid vinyl esters as acyl donors and commercial CAL-B.     

功能离子液体复合体系中钯催化的Heck偶联反应

在[BMIM][TPPMS]离子型膦配体和碱性离子液体 [BMIM][OAc] 组成的功能离子液体复合体系中, PdCl2(CH3CN)2可以有效地催化溴苯和丙烯酸乙酯的交叉偶联(Heck)反应, 产物肉桂酸乙酯(反式)的收率达到60%. 锚定在功能离子液体复合体系中的Pd催化剂循环使用11次后仍保持良好的活性和稳定性. 该催化剂体系的良好活性和稳定性可归因于三个方面: [BMIM][TPPMS]和[BMIM][OAc]间的协同配位效应; 以[BMIM][OAc]作为Heck反应的缚酸剂, 避免了无机盐粘稠物的形成; 生成的副产物[BMIM]Br可以有效溶解钯黑, 避免了钯黑的析出. 该离子液体催化体系对不同底物的Heck偶联反应也表现出良好的普适性.