碱性离子液体催化的Claisen-Schmidt缩合反应

合成了6种以N-甲基咪唑为基体的碱性离子液体, 以其作为催化剂, 在无溶剂条件下, 成功催化了Claisen-Schmidt缩合反应. 采用Hammett指示剂法对碱性离子液体的碱性强度和碱量进行表征. 实验结果表明, 此系列碱性离子液体对Claisen-Schmidt缩合反应具有较高的催化活性, 反应条件温和, 产物产率较高, 离子液体经简单处理后可多次循环使用, 催化活性未见明显降低.     

咪唑根碱性离子液体在水介质Knoevenagel反应中的催化作用

报道了咪唑根1-丁基-3-甲基咪唑([Bmim]Im)碱性离子液体的合成与表征,该离子液体具有强碱性和较好的热稳定性.碱性离子液体[Bmim]Im用于催化水介质中Knoevenagel反应,发挥了碱催化剂与相转移催化剂双重作用.此外,离子液体[Bmim]Im及其水溶液还具有良好的循环使用性能.水介质、低催化剂用量、室温...     

咪唑阴离子型碱性离子液体的合成及其催化Knoevenagel缩合反应

设计合成了由1-丁基-3-甲基咪唑阳离子与咪唑阴离子搭配的[bmim]Im新型碱性离子液体并对其碱性进行研究.[bmim]Im离子液体的碱性与[bmim]OH的碱性接近且强于[bmim]OAc.在水溶液及室温条件下,2%的[bmim]Im离子液体对系列芳香醛与活泼的亚甲基化合物之间的Knoevenagel缩合反应具有较好的催化性能,目标产物的收率达到86%～95%,选择性为100%.同时,该催化剂体系具有良好的循环性能.     

离子液体[bmim][PF6]与[moemim][PF6]结构微不均匀性以及微粘度的光谱探测

室温离子液体由于其极低的蒸汽压、比较好的热稳定性和化学稳定性、良好的分子结构与性能的可设计性等优点,作为一种新型的环境友好溶剂在很多领域有着广泛的应用.对于离子液体的微观结构和微观性能的研究是设计新型离子液体以及扩展离子液体应用的关键.本文通过荧光探针分子香豆素153(C153)的转动动力学和对微观环境敏感的荧光探针分子1, 3-二(1-芘基)丙烷(BPP)的稳态荧光光谱,探测和表征了烷基取代的离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bmim][PF₆])和与其具有相似结构的醚键官能化的离子液体1-甲氧基乙基-3-甲基咪唑六氟磷酸盐([moemim][PF₆])的微观结构和微粘度. C153探针分子在离子液体[bmim][PF₆]中的转动过程具有快、慢两个组分表明离子液体[bmim][PF₆]内部存在松散和紧密的两种结构微区;而C153探针分子在离子液体[moemim][PF₆]中的转动动力学只存在一种过程,说明醚键的引入使得[moemim][PF₆]内部趋于一种类型的微环境.通过C153探针分子的转动时间研究发现,醚键官能化的离子液体[moemim][PF₆]的微粘度小于烷基链取代的离子液体[bmim][PF₆],同时通过BPP探针分子的二聚体激基复合物(excimer)与单体(monomer)荧光发射强度的比值(I_E/I_M)研究也证明这一结果.醚键的引入使得离子液体[moemim][PF₆]相对于离子液体[bmim][PF₆],侧链的极性更大、柔顺性更好,同时醚键有可能作为氢键的受体与阳离子形成氢键从而削弱离子液体中阴、阳离子间的相互作用,使得离子液体[moemim][PF₆]的微观环境比离子液体[bmim][PF₆]更为均一,同时具有更小的微粘度.     

Schiff碱式双功能离子液体的制备与表征

分步合成法了Schiff碱式双反应中心的功能化离子液体: 首先通过1-丙胺基-3-甲基咪唑氯与FeCl₃合成含有-NH₂的Fe基离子液体; 然后通过1,3-二氨基-2-丙醇与3,5-二叔丁基水杨醛合成Schiff碱配体H₂L及其Co配合物CoL, 再通过4-氯丁酰氯的酰氯基与配合物CoL的-OH反应生成含有-CH₂Cl的配合物CH₂Cl-CoL; 最后通过Fe基离子液体的-NH₂与配合物CH₂Cl-CoL的-CH₂Cl之间的键合反应合成Schiff碱式双功能离子液体. 通过有机元素分析、 红外光谱、 紫外-可见光谱、 核磁共振波谱、 电喷雾电离质谱、 电感耦合等离子体-质谱和拉曼光谱对各化合物进行了结构表征, 确定Schiff碱式双功能离子液体的阳离子为Schiff碱Co络合阳离子, 阴离子为Fe的络合阴离子.     

N-羧基吡啶功能化离子液体的表征

合成了系列新型N-羧基吡啶功能化离子液体, 利用1H NMR、13C NMR、IR、DSC对其进行表征并研究了其与常规溶剂的相溶性, 采用酸碱滴定法测量了系列离子液体的酸离解常数pKa值. N-羧基取代吡啶功能化离子液体的pKa值在2.5~4.0之间, 并随阳离子取代羧基碳链的增长而增大; 离子之间形成氢键及阴、阳离子的大小是影响离子液体熔点的主要因素. 阴离子越小, 熔点越高. 所合成的N-羧基吡啶功能化离子液体具有相同的相溶性且由取代羧基所决定, 与常见烷基咪唑离子液体相比, N-羧基吡啶功能化离子液体与丙酮、二氯甲烷并不相溶. 功能化离子液体的阳离子取代基是影响其物化性能的主要因素, 通过改变功能化基团碳链的长短及与不同阴离子进行组合, 可以对功能化离子液体物理、化学性能进行调节.     

1-烷基-3-甲基咪唑系列室温离子液体表面张力的研究

合成了系列1-烷基-3-甲基咪唑四氟硼酸盐([C_2～7mim]BF₄)及六氟磷酸盐([C_4～7mim]PF₆)室温离子液体, 并通过核磁氢谱、红外光谱、质谱等手段对其进行了结构表征; 采用Wilhelmy白金板法, 在293～338 K范围内测定了离子液体的表面张力, 测试结果显示, 同类离子液体表面张力γ随温度的升高而线性下降, 同种离子液体的表面张力呈现出较宽的变化范围, 如293 K下, 表面张力值从[C₂mim]BF₄的50.4 mJ/m²到[C₇mim]BF₄的36.1 mJ/m². 最后对离子液体的表面性能进行了讨论.     

Pd/羧基功能化离子液体选择性催化氧化苯乙烯

 利用羧基对咪唑型离子液体的阳离子进行功能化,得到一系列具有不同羧基数目及与不同阴离子搭配的N-羧基功能化咪唑离子液体(TSILs), 进而构筑PdCl2/TSILs催化剂体系. 以过氧化氢为氧化剂,将PdCl2/TSILs用于选择性催化氧化苯乙烯合成苯乙酮. 研究结果表明, PdCl2/TSILs催化体系对目标反应具有理想的催化性能,羧基功能化离子液体的阳离子及其搭配的阴离子对苯乙酮的选择性和产率均有显著的影响. 阳离子的羧基数目越多,阳离子的不对称性越高, PdCl2/TSILs催化剂体系的活性越好. 含有相同阳离子的PdCl2/TSILs催化剂体系,其催化性能按照阴离子PF-6＜H2PO-4＜Cl-＜BF-4的顺序递增且与其酸强度顺序相反. 含有三羧基的功能化离子液体与PdCl2构筑的催化剂体系具有最佳的催化性能,在55 ℃下,该催化剂体系的转换频率值达到125 h-1, 苯乙烯可以完全转化且苯乙酮的选择性为91%.     

阳离子取代基对离子液体气相色谱固定相保留性能的影响

以双-三氟甲烷磺酰亚胺离子（［NTf₂］^-）、三氟甲基磺酸根离子（［TFO］^-）和六氟磷酸根离子（［PF₆］^-）为阴离子,合成了含有丙基、丁基、壬基、乙苯基或氰甲基等阳离子取代基的聚合乙烯基咪唑基离子液体固定相,制备了13种离子液体石英毛细管色谱柱。考察了离子液体固定相结构与色谱柱McReynolds常数、热稳定性和测试化合物保留行为之间的构效关系,研究了阳离子取代基对固定相保留性能的影响规律;同时考察了测试化合物保留指数随温度变化的规律。结果表明,所合成的离子液体固定相具有较强的极性,其保留性能不仅与阳离子取代基的性质密切相关,而且受取代基结构和阴离子影响明显;在考察的温度范围内,测试化合物的保留指数变化规律与传统色谱固定相完全相同。     

硅烷基咪唑双三氟甲烷磺酰亚胺离子液体气相色谱固定相的性能评价

以双三氟甲烷磺酰亚胺离子([NTf₂]^-)为阴离子,合成阳离子烷基取代不同(C1、C2和C4)的硅烷基咪唑离子液体,以其为固定相制备气相色谱填充柱。 硅烷基咪唑离子液体为强极性固定相;阳离子结构影响固定相的热稳定性、极性和分离性能。 在这些离子液体固定相中,1-丁基-3-[(3-三甲氧基硅基)-丙基]咪唑双三氟甲烷磺酰亚胺([PBIM]NTf₂)对Grob试剂分离性能较好。 利用溶剂化作用参数模型,评价[PBIM]NTf₂固定相特性,研究固定相-组分分子之间相互作用机制;同时考察[PBIM]NTf₂色谱柱对不同类型化合物的分离性能。 结果表明,[PBIM]NTf₂固定相主要作用力是氢键碱性和偶极作用,对烷烃、醇、酯和胺等不同类型的样品组分表现出良好的分离能力。     

Degradation of polylactide using basic ionic liquid imidazolium acetates

Imidazolium acetate ionic liquids show high efficiency in the degradation of polylactides (PLA): degradation degree of PLA can reach almost 100 % in imidazolium acetate ionic liquids at 170°C and 1 h under atmospheric pressure, while the degradation degree of PLA remains close to 0 % using neutral 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and acidic ionic liquids at the same reaction conditions. With the increase of both the amount of acetate ionic liquid and the reaction temperature, the degradation degree of PLA increases. The structure of ionic liquids affects the degradation behavior of PLA: for cations, the proton from the C-2 position on the imidazolium ring is involved in the degradation of PLA; the degradation of PLA increases with the increase of the alkyl side-chain length of imidazolium cations; for anions, moderate basicity of the acetate ion contributes to the high activity of the imidazolium acetate ionic liquids in the degradation of PLA.     

双核碱性离子液体催化棉籽油酯交换制备生物柴油

采用两步法制备了五种新型咪唑类碱性双核功能化离子液体化合物,并考察了对棉籽油酯交换制备生物柴油的催化性能。结果表明,咪唑类碱性双核功能化离子液体具有很好的催化活性,其催化活性与阳离子中碳链长度有关。其中,双-(3-甲基-1-咪唑)亚乙基双氢氧化物离子液体的催化活性最好。催化剂量、反应时间、反应温度及醇油比对生物柴油中脂肪酸甲酯含量及选择性影响的研究发现,在催化剂用量为0.4%(质量分数),醇油摩尔比为12,反应温度为55℃,反应时间为4 h时,脂肪酸甲酯的含量和选择性分别达98.5%和99.9%。催化剂7次循环后,产物中脂肪酸甲酯含量仍达到96.2%,单甘酯和双甘酯的含量很少,表明该催化剂重复使用良好。     

Suppression of deleterious effects of free silanols in liquid chromatography by imidazolium tetrafluoroborate ionic liquids

Silica-based stationary phases are commonly used in liquid chromatography, but their surface acidity causes known problems, especially when separating basic compounds. Deleterious effects of free silanols are not fully removed by standard prevention procedures consisting in adding alkylamines or other amino quenchers to the eluents. We found that ionic liquids of the imidazolium tetrafluoroborate class, added to mobile phases at concentrations of 0.5-1.5% (v/v), blocked silanols and provided excellent thin-layer chromatographic separations of strongly basic drugs which were otherwise not eluted, even with neat acetonitrile as the mobile phase. The silanol suppressing potency of imidazolium tetrafluoroborates was demonstrated to markedly exceed that of the standard mobile phase additives, like triethylamine, dimethyloctylamine and ammonia. The proposed new mobile phase additives were also demonstrated to provide reliable lipophilicity parameters of base drug analytes as determined by gradient mode of high-performance liquid chromatography. By applying the readily available and environmentally friendly imidazolium tetrafluoroborate ionic liquids, simple and efficient means of improvement of liquid chromatographic analysis of organic bases were elaborated.     

Terahertz time-domain spectroscopy of imidazolium ionic liquids

We have measured the terahertz (THz) complex dielectric spectra of imidazolium ionic liquids by THz time-domain spectroscopy (THz-TDS) in the frequency range from 5 (0.15 THz) to 140 cm(-1) (4.2 THz). The ionic liquids investigated are 1-ethyl-3-methylimidazolium (EMIm+)/trifluoromethanesulfonate (TfO-), EMIm+/tetrafluoroborate (BF(4)-), 1-butyl-3-methylimidazolium (BMIm+)/TfO-, and BMIm+/BF(4)-. The dielectric values of the ionic liquids in the THz region are similar to those of short-chain alcohols. The THz dielectric values are related to subpicosecond-to-picosecond dynamics. The same trend has been observed in the empirical polarity ET(30) although it is related to the static characteristics of polarity and hydrogen bonding ability. A difference between the two types of liquids is observed in the THz dielectric spectral shapes: the ionic liquids show structured lineshapes but short-chain alcohols show much less structured ones. The structured lineshapes of the ionic liquids reflect the low-frequency motions of interion and/or intramolecular vibrations. When the ionic liquids composed of the different imidazolium cations contain the same anions as counterions, their density-normalized THz dielectric spectra above 20 cm(-1) bear strong resemblance to each other in shape and magnitude. It shows clearly that the THz spectra do not originate from the intramolecular vibrations of the imodazolium cations. All of the intramolecular vibrations of the anions are located above 140 cm(-1) except the CF3-SO3 torsion of TfO-, the band of which alone cannot explain the broad THz dielectric spectra of the ionic liquids. Therefore, we conclude that the interion vibrations rather than the intramolecular vibrations dominantly contribute to the THz dielectric spectra. The results strongly indicate that even in the liquid phase the ionic liquids have local structures similar to their solid-phase structures.     

A New Method for Predicting Decomposition Temperature of Imidazolium‐based Energetic Ionic Liquids

Two novel correlations are introduced to predict decomposition temperatures of imidazolium‐based energetic ionic liquids. The first simple model is based only on the number of some of atoms in cationic and anionic structures. Meanwhile, a suitable correction term was added in the second correlation to adjust the predicted results for the presence of some specific cation/anion moieties. The measured data of 164 different types of imidazolium‐based energetic ionic liquids were used to derive the new correlations. The calculated mean absolute percent errors (MAPEs) of the first and second models are 6 and 4, respectively. The predicted results have confirmed that insertion of correcting function in the second correlation can provide better estimations. These models were also tested and compared with one of the best available group contribution methods, where group contribution method can be applied, for 17 further imidazolium‐based energetic ionic liquids containing complex molecular structures. Furthermore, the predicted values of MAPEs of the new models are close to that of obtained by group contribution method.     

咪唑醋酸离子液体热力学性质的理论研究

咪唑醋酸离子液体在催化、电化学、萃取等领域具有潜在的应用价值,对其热力学性质的深入研究将为其应用提供理论依据。本文采用密度泛函理论(DFT)方法和Born-Fajans-Haber (BFH)循环法对咪唑醋酸离子液体[C_nmim][OAc] (n=1-6)进行热力学性质的理论研究。计算其相变过程中的解离焓、汽化焓、熔化焓、晶格焓、溶解焓等,并与已有实验值进行比较。利用Gaussian 09程序在B3LYP/6-311+G(d, p)和M062X/TZVP两种水平下计算解离焓值,同时通过计算得到分子体积和总气相能的焓修正值,借助Matlab计算软件拟合得到汽化焓值,取得与已有实验值很好的一致性。使用Jenkins公式求得晶格能,计算得到晶格焓,最后利用BFH循环计算得到溶解焓。     

Continuous Synthesis of Peralkylated Imidazoles and their Transformation into Ionic Liquids with Improved (Electro)Chemical Stabilities

A versatile and efficient method to synthesize tetrasubstituted imidazoles via a one‐pot modified Debus–Radziszewski reaction and their subsequent transformation into the corresponding imidazolium ionic liquids is reported. The tetrasubstituted imidazoles were also synthesized by means of a continuous flow process. This straightforward synthetic procedure allows for a fast and selective synthesis of tetrasubstituted imidazoles on a large scale. The completely substituted imidazolium dicyanamide and bis(trifluoromethylsulfonyl)imide salts were obtained via a metathesis reaction of the imidazolium iodide salts. The melting points and viscosities are of the same order of magnitude as for their non‐substituted analogues. In addition to the superior chemical stability of these novel ionic liquids, which allows them to be applied in strong alkaline media, the improved thermal and electrochemical stabilities of these compounds compared with conventional imidazolium ionic liquids is also demonstrated by thermogravimetrical analysis (TGA) and cyclic voltammetry (CV). Although increased substitution of the ionic liquids does not further increase thermal stability, a definite increase in cathodic stability is observable.     

Novel ascorbic acid based ionic liquids for the in situ synthesis of quasi-spherical and anisotropic gold nanostructures in aqueous medium

A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi-spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1-alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3-methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature (Tg) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape-directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry-like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.     

咪唑盐类聚离子液体抗菌剂的制备及其在水凝胶敷料中的应用

皮肤伤口的感染严重威胁患者的生命安全,虽然传统的含有银离子或小分子抗生素的抗菌水凝胶伤口敷料具有广谱的杀菌功效,但这些抗菌水凝胶敷料中的抗菌剂存在一定的生物毒性和耐药性风险,无法满足临床长期使用的要求.咪唑盐类聚离子液体由于其含有较强的正电荷效应以及疏水链段,因此其作为新型的聚合物抗菌剂具有较强的抗菌效果.本研究首先通...