离子液体[BMIM]Br与[BMIM][BF4]配比浓度对Br-离子电荷转移的调节

利用X射线吸收精细结构光谱(XAFS)及紫外吸收光谱两种方法, 分析了离子液体1-丁基-3-甲基咪唑溴盐([BMIM]Br)中逐渐掺入1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])时, Br^-阴离子与咪唑阳离子之间氢键作用及电荷偏移量的改变. 随着[BMIM][BF₄]加入量增多, Br 元素XAFS近边(XANES)显示吸收峰降低, 吸收边位置向低能端位移0.9 eV; 扩展边(EXAFS)算出径向结构显示Br 与近邻原子间平均配位数降低、平均键长增长; 紫外光谱也有明显蓝移减色效应. 这些结果都表明Br₄^-的掺入改变了Br^-与阳离子间的电荷偏移量, 负电荷更多地转移到Br^-上, 量化计算的数据同样支持该结论.     

离子液体1-烷基-3-甲基咪唑四氟硼酸盐在水溶液中的聚集行为

采用等温滴定量热法、静态荧光猝灭法和电导法系统研究了典型离子液体1-烷基-3-甲基咪唑四氟硼酸盐([Cnmim][BF₄])在水溶液中的聚集行为, 获得了胶束形成的临界胶束浓度(cmc), 摩尔焓变(ΔH_mic), 摩尔吉布斯自由能变(ΔG_mic), 摩尔熵变(ΔS_mic)以及不同浓度时[Cnmim][BF₄]胶束的平均聚集数等基本参数. 发现这类离子液体的聚集为熵驱动, 阳离子的烷基链越长, ΔG_mic越负, 聚集更容易发生. 此外, 结合[C_nmim]X (X=Cl^-, Br^-)的相关研究发现, 阳离子相同时, 体积越大和疏水性越强的阴离子与头基的结合能力越强, 能有效地降低头基之间的静电排斥, 降低cmc, 利于胶束的形成. 对于[C₁₂mim][BF₄], 添加剂β-环糊精(β-CD)的加入可使cmc增大, ΔH_mic和ΔS_mic减小, 而KBF₄则可使cmc和ΔH_mic减小, ΔS_mic增大.     

离子液体催化吲哚羟烷基化反应

报道了咪唑类离子液体催化吲哚和环状碳酸酯反应合成羟烷基吲哚,系统考察了反应时间、催化剂用量、反应温度和反应物比例对离子液体催化反应性能的影响.在优化的反应条件下,吲哚与碳酸乙烯酯或碳酸丙烯酯反应可高效地生成1-(2-羟乙基)吲哚、1-(2-羟丙基)吲哚及其相应的衍生物.离子液体的催化活性与离子液体中的阴离子有关,其催化活性顺序为BF₄^-﹤Br^-﹤Cl^-﹤OAc^-,与阴离子的碱度顺序一致.     

分子模拟研究气体在室温离子液体中的溶解度

在作者先前建立的分子力场基础上, 采用Widom粒子插入法预测了CO₂、N₂、O₂、Ar及CH₄等5种气体在多种咪唑类离子液体中的溶解度, 包括2种侧链长度的阳离子和3种阴离子. 首先考察了256个离子对组成的体系中溶质分子插入次数对计算结果的影响, 在此基础上计算了不同温度下气体在1-丁基-3-甲基咪唑的四氟化硼盐([bmim][BF₄])和六氟化磷盐([bmim][PF₆])中的溶解度. 计算结果正确反映了CO₂气体溶解度的变化趋势, 在[bmim][BF₄]中溶解度的模拟结果与实验值符合很好, 且明显优于Pádua等的模拟结果；在[bmim][PF₆]中的溶解度较实验值偏高, 精度与文献模拟结果相当；并预测了较高温度下CO₂气体在[bmim][BF₄]和[bmim][PF₆]中的溶解度. 计算结果也正确地反映了5种气体在[bmim][PF₆]中溶解度实验值的相对大小. 另外考察了常温下几种气体在不同室温离子液体中的溶解度, 模拟结果表明气体在含有较长碳链和双-三氟甲基磺酰胺阴离子(Tf₂N^－)的离子液体中溶解度较大.     

离子液体[bmim][BF4]对联苯甲酰光化学反应影响的瞬态吸收光谱

利用纳秒级激光光解瞬态吸收光谱研究了联苯甲酰(BZ)在离子液体1-丁基-3-甲基咪唑四氟硼酸盐([bmim][BF₄])与乙腈(MeCN)混合体系中的光化学反应行为. 考察了探针分子BZ存在下[bmim][BF₄]/MeCN比例对体系中化学反应动力学的影响. 实验发现: 在N₂饱和条件下, BZ溶液经激光辐照后产生的激发三线态³BZ^*遵循一级反应动力学规律衰减. 离子液体(IL)相对比例增加对³BZ^*瞬态吸收峰的位置和强度没有产生明显影响. 但离子液体体积分数V_IL的变化对[bmim][BF₄]/MeCN混合溶剂中光诱导电子转移的影响却非常显著, 总体上电子转移产生的自由基的表观生成速率常数k_gr随[bmim][BF₄]的V_IL增大而减小. 在[bmim]BF₄]比例足够大的情况下, ³BZ^*与三乙胺或四甲基对苯二胺之间的电子转移被抑制.     

三种马来二腈基二硫烯镍(Ⅲ)离子对配合物的制备和结构表征

合成了3种离子对配合物 [1-benzyl-3-bromopyridium]⁺[Ni(mnt)₂]^- (1)，[1-(4′-flurobenzyl)-3-bromopyridiunm]⁺[Ni(mnt)₂]^- (2)，[1-(4′-cholorobenzyl)-3-bromopyridium]⁺[Ni(mnt)₂]^- (3)，(mnt=马来二腈基二硫烯，maleonitrile dithiolate)获得了单晶并解析了它们的单晶结构。     

[Me3NC2H4OH]Zn2Cl5水溶液的激光光解研究

利用时间分辨激光光解技术研究了季铵盐型离子液体[Me₃NC₂H₄OH]Zn₂Cl₅(简写R-Zn₂Cl₅)的光解行为, 研究发现离子液体能被266 nm激光单光子电离, 生成阳离子自由基、[Zn₂Cl₅]^•中性自由基和水合电子, 观察到胆碱激发三线态的存在, 并测定了离子液体光电离的量子产额为0.04. 利用266 nm激光对离子液体、胆碱、氯化锌、氯化钠的光解行为比较, 发现胆碱阳离子的贡献很小, [Zn₂Cl₅]^－阴离子起主要作用. 采用氧化性自由基SO₄^•－引发离子自由基, 揭示其光电离机理, 测定离子液体的动力学反应速率常数, SO₄^•－ 460 nm的衰减速率常数为1.3×10⁹ L•mol^－1•s^－1, 320 nm离子自由基瞬态产物的生成速率常数为1.5×10⁹ L•mol^－1•s^－1, 两者很接近, 说明SO₄^•－自由基的衰减与瞬态自由基的生成是同步的.     

离子液体-分子溶剂混合体系中电导率的测量与关联

在298.15K下测定了1-正丁基-3-甲基咪唑四氟硼酸盐([Bmim][BF₄])和1-正丁基-3-甲基咪唑六氟磷酸盐([Bmim][PF₆])与不同分子溶剂混合体系的电导率。结果表明, 随着分子溶剂浓度的增大，离子液体的摩尔电导率逐渐增大，离子液体在溶液中的摩尔电导率可以用纯离子液体的摩尔电导率、分子溶剂的介电常数和摩尔体积进行关联。     

离子对间电荷转移配合物：阴离子…π作用及近红外吸收

合成并表征了一种离子对配合物1,[Cl₂Bz-1-Apy]₂[Ni(mnt)₂],其中,Cl₂Bz-1-Apy为(E)-1-(3,4-二氯苯亚甲基氨基)吡啶一价阳离子,mnt是马来二睛基二硫烯二价阴离子。在配合物1的晶体中,阴离子和阳离子中吡啶环之间存在阴离子…π相互作用。DFT电荷密度分布分析表明,阴离子…π相互作用主要源自离子对间的Coulomb吸引力。在固体和乙腈溶液电子吸收光谱近红外区,配合物1都有一个宽的弱吸收带,该吸收带可归属为二价阴离子[Ni(mnt)₂]^2-内的d-d电子跃迁和阴阳离子对间的电荷转移跃迁。     

抗衡阴离子PF6-调控的1, 3-丙二胺缩邻香兰素镧(Ⅲ)配合物的合成和晶体结构

通过柔性配体1, 3-丙二胺缩邻香兰素(H₂L)与和La(NO₃)₃·6H₂O反应, 合成了1个由2个H₂L桥连的双核稀土配合物[La₂(NO₃)₆(H₂L)₂] ·CH₂Cl₂ (1), 该配合物与(NH₄)(PF₆)继续反应生成了1个由2个NO₃^-离子桥连的双核配合物[La₂(NO₃)₂(H₂L)₄] (PF₆)₄·4H₂O·2CH₂Cl₂ (2), X-射线单晶衍射分析确定了2个配合物的晶体结构。配合物1和2为结构完全不同的2个双核结构, 因抗衡阴离子PF₆^-有去阴离子的作用, 配合物1中的NO₃^-离子被配体取代, 导致配合物1的结构翻转, 形成了1个新颖的双核结构2。     

Ionic Association of the Ionic Liquids [C4mim][BF4], [C4mim][PF6], and [Cnmim]Br in Molecular Solvents

Considering the ionic nature of ionic liquids (ILs), ionic association is expected to be essential in solutions of ILs and to have an important influence on their applications. Although numerous studies have been reported for the ionic association behavior of ILs in solution, quantitative results are quite scarce. Herein, the conductivities of the ILs [C_nmim]Br (n=4, 6, 8, 10, 12), [C₄mim][BF₄], and [C₄mim][PF₆] in various molecular solvents (water, methanol, 1‐propanol, 1‐pentanol, acetonitrile, and acetone) are determined at 298.15 K as a function of IL concentration. The conductance data are analyzed by the Lee–Wheaton conductivity equation in terms of the ionic association constant (K_A) and the limiting molar conductance (Λ_m⁰). Combined with the values for the Br^? anion reported in the literature, the limiting molar conductivities and the transference numbers of the cations and [BF₄]^? and [PF₆]^? anions are calculated in the molecular solvents. It is shown that the alkyl chain length of the cations and type of anion affect the ionic association constants and limiting molar conductivities of the ILs. For a given anion (Br^?), the Λ_m⁰ values decrease with increasing alkyl chain length of the cations in all the molecular solvents, whereas the K_A values of the ILs decrease in organic solvents but increase in water as the alkyl chain length of the cations increases. For the [C₄mim]⁺ cation, the limiting molar conductivities of the ILs decrease in the order Br^?>[BF₄]^?>[PF₆]^?, and their ionic association constants follow the order [BF₄]^?>[PF₆]^?>Br^? in water, acetone, and acetonitrile. Furthermore, and similar to the classical electrolytes, a linear relationship is observed between ln K_A of the ILs and the reciprocal of the dielectric constants of the molecular solvents. The ILs are solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation. This information is expected to be useful for the modulation of the IL conductance by the alkyl chain length of the cations, type of anion, and physical properties of the molecular solvents.     

Ionic liquid assisted synthesis of flowerlike Cu2O micro-nanocrystals

Novel flowerlike Cu2O micro-nanocrystals were prepared by a greener reductive reaction of cupric acetate monohydrate with ethylene glycol in aqueous solutions of [C8mim]X (X = Cl , Br , BF4 , PF6 ) and [Cnmim][BF4] (n = 4, 6, 8). The obtained microstructures of Cu2O were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR). The effects of cations, anions and concentration of the ionic liquids on the morphology of Cu2O were examined in some details. The results suggest that the formation of flowerlike Cu2O was governed by a [C8mim][BF4] controlled reductive reaction mechanism. As one of their applications, the Cu2O nanoparticles were used for the photocatalytic degradation of methylene blue in aqueous solution, and high photocatalytic activity was observed.     

Rapid Preparation of Silsesquioxane‐Based Ionic Liquids

Three new hybrid ionic liquids (ILs) based on cage silsesquioxane (SQ) were rapidly prepared in high yields from octa(mercaptopropyl)silsesquioxane and 1‐allyl‐3‐methylimidazolium salts (Br^?, BF₄^?, PF₆^?) through the photochemical thiol–ene reaction. These SQ‐based ILs exhibited low glass transition temperatures and good thermal stability. The unique amphiphilic nature of these hybrid ILs cause them to self‐assemble into perfect vesicles with “yolk–shell” structures, in which cages formed the “yolk” due to their aggregation and outer anions formed the “shell”.     

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.     

Role of C2 methylation and anion type on the physicochemical and thermal properties of imidazolium-based ionic liquids

This study focused on the effects of methylation and different anions (Br^? and Cl^?) on the physicochemical and thermal properties of [C₁₆MIM]X and [C₁₆MMIM]X, belonging to the imidazolium-based ionic liquid (IL) family. The effect of methylation on the transmittance in the fingerprint region of the Fourier transform infrared (FT-IR) spectrum was observed as a blue shift, and a new peak associated with the C-N stretching bond was obtained. In contrast, in the functional group region, the frequency shift was related to the change in the vibrational mode from C2-H-X to C2-methyl-X. In general, methylation resulted in an increase in decomposition temperature, an increase in melting temperature, and a decrease in melting enthalpy, leading to a reduction in entropy. The trends observed for the decomposition temperature, melting temperature, and melting enthalpy with different anions depended on the strength of the Brønsted acids and hydrogen bonds of the Br^? and Cl^? based anions. The thermal conductivity of the methylated ILs increased with an increase in temperature. In contrast, for the non-methylated (protonated) ILs, the thermal conductivity of [C₁₆MIM]Br decreased with an increase in temperature, while the opposite trend was observed for [C₁₆MIM]Cl. The data were compared with those of the short alkyl chain and weakly coordinating anion of NTf₂. The analysis was performed considering different phases, the prominent role and different behaviour in the hydrogen bonding at the C2 position of the imidazolium ring upon methylation, and the significant change in viscosity, which can influence the IL structure.     

Effect of Ionic Liquids on Catalytic Characteristics of Horse Liver Alcohol Dehydrogenase

The catalytic characteristics of horse liver alcohol dehydrogenase （HLADH） in the systems involving ionic liquids （ILs） （BMIm·Cl, BMIm·Br, BMIm·PF6, BMIm·BF4 BMIm·OTf and EMIm·Cl） were examined. HLADH displayed higher oxidation activity towards ethanol in the systems containing BMIm·Cl, BMIm·Br, EMIm·Cl or BMIm·PF6 with proper content than that in the IL-free buffer. An excessive amount of these ILs in the reaction systems resulted in an obvious decline in enzymatic activity. BMIm·BF4 and BMIm·OTf of any content investigated could considerably inhibit the enzyme. The anions of ILs showed significant effect on the activity, kinetic parameters and activation energy of HLADH-mediated ethanol oxidation. Additionally, BMIm·Cl, BMIm·Br, EMIm·Cl and BMIm·PF6 boosted markedly the thermostability of HLADH, while the enzyme was less thermostable in BMIm·BF4 or BMIm·OTf-containing systems. The associated conformational changes in HLADH caused by ILs were examined by UV technique.     

Synthesis of TiO2 hollow spheres using binary ionic liquids as an electrocatalyst

Titanium dioxide (TiO₂ titania) hollow sphere was simply synthesized using various ionic liquids (ILs). The shape and size of TiO₂ particles were significantly different with the composition of ILs. This is mainly attributed to the interaction between organic solvent and IL at the interface leading to the formation of sphere. Among the binary ILs, [Bmim][BF₄] + [Omim][PF₆], [Bmim][BF₄] + [Omim][PF₆], and [Bmim][PF₆] + [Hmim][PF₆] were useful to prepare TiO₂ nanostructures with high surface area and anatase phase. Especially, [Bmim][BF₄] + [Omim][PF₆] was the most effective IL to synthesize an anatase TiO₂ hollow sphere.

     

Absolute Brønsted Acidities and pH Scales in Ionic Liquids

Although receiving large interest over the last years, some fundamental aspects of Brønsted acidity in ionic liquids (ILs) have up to now been insufficiently highlighted. In this work, standard states, activity, and activity coefficient definitions for IL solvent systems were developed from general thermodynamic considerations and then extended to a general mixed solvent standard state. By using the bromide/bromoaluminate systems as representative ILs, formulae for thermodynamically consistent pH scales for ILs with simple (Br^?) and complex ([Al_nBr_3n+1]^?) anions were derived on the basis of the chemical potential of the proton. Supported by quantum chemical [ccsd(t)/MP2/DFT/COSMO‐RS] calculations, Gibbs solvation energies of the proton were calculated, which allowed the ILs to be ranked in absolute acidity, that is, pH_abs or μ_abs(H⁺, IL), and additionally allowed their acidity to be compared with molecular Brønsted acid systems. It was shown that bromoaluminate ILs are suited for reaching superacidic conditions. The complexity of autoprotolysis processes in C₆MIM⁺[AlBr₄]^? (C₆MIM=1‐hexyl‐3‐methylimidazolium) with or without the addition of basic (i.e. Br^?) or acidic (AlBr₃ and/or HBr) solutes was examined in detail by model calculations, and they indicated a large thermodynamic influence of small deviations from the exact stoichiometric composition.     

Chiral Pyrrolidinium Ionic Liquids with (−)-Borneol Fragment in the Cation – Synthesis,Physicochemical Properties and Application in Diels-Alder Reaction

A series of chiral pyrrolidinium salts containing (1 S)-endo-(−)-born-2-yloxymethyl substituent in the structure of the cation and six different anions: chloride, tetrafluoroborate [BF₄]⁻, hexafluorophosphate [PF₆]⁻, trifluoromethanesulfonate [OTf]⁻, bis(trifluoromethylsulfonyl)imide [NTf₂]⁻, bis(pentafluoroethylsulfonyl)imide [NPf₂]⁻ and perfluorobutanesulfonate [C₄FS]⁻ were efficiently prepared and extensively characterized. The enantiomeric purity of them was confirmed by NMR analysis with a chemical shift reagent. All salts were characterized with the specific rotation, the solubility in commonly used solvents, thermal properties, including phase transition temperatures and thermal stability. Salts with [PF₆]⁻, [C₄FS]⁻, [NTf₂]⁻ and [NPf₂]⁻ anions were classified as chiral ionic liquids (CILs). Moreover, salts with [NTf₂]⁻ and [NPf₂]⁻ anions were in the liquid state at room temperature and below. Therefore, density and dynamic viscosity, the surface tension and the contact angle on three different surfaces were also measured for them. Additionally, these chiral ionic liquids were tested as solvents in Diels-Alder reaction.     

Room-Temperature Synthesis of the Bi5[GaCl4]3 Salt From Three Different Classes of Ionic Liquids

Following the development in the synthesis of subvalent cluster compounds, we report on the use of three different classes of room-temperature ionic liquids for the synthesis of the pentabismuth-tris(tetragallate) salt, Bi₅[GaCl₄]₃, characterized by X-ray diffraction. The Bi₅[GaCl₄]₃ salt was prepared by reduction of BiCl₃ using gallium metal in ionic liquid reaction media containing a strong Lewis acid, GaCl₃. The ionic liquids; trihexyltetradecyl phosphonium chloride [Th-Td-P⁺]Cl^?, 1-dodecyl-3-methylimidazolium chloride [Dod-Me-Im⁺]Cl^? and N-butyl-N-methylpyrrolidinium chloride [Bu-Me-Pyrr⁺]Cl^? from three of the main classes of ionic liquids were used in synthesis. Reactions using ionic liquids composed of the trihexyltetradecyl phosphonium cation [Th-Td-P⁺] and the anions; tetrafluoroborate [BF₄ ^?], bis(trifluoro-methyl sulfonyl) imide [(Tf)₂N^?] and hexafluorophosphate [PF₆ ^?] were also investigated.