Prediction of the heat capacity of ionic liquids using the mass connectivity index and a group contribution method

A simple and accurate group contribution method to estimate the heat capacity of ionic liquids is presented. The method considers groups previously defined for a successful method used to estimate critical properties of ionic liquids. Additionally a structural parameter known as mass connectivity index recently defined by the authors has been incorporated to define the model equation. To better define the values of the groups, heat capacity data at 298 K for 126 organic substances were used with the 469 heat capacity data for 32 ionic liquids. The results were compared with experimental data and with values reported by other available estimation methods. Results show that the new group contribution method gives low deviations and can be used with confidence in thermodynamic and engineering calculations.     

Estimation of the thermal conductivity λ(T,P) of ionic liquids using a neural network optimized with genetic algorithms

In this study, an artificial neural network was optimized using a genetic algorithm in order to estimate the thermal conductivity of ionic liquids at different temperatures and pressures. Experimental thermal conductivity data of 41 ionic liquids (400 experimental data points) in the range from 0.10 to 0.22 W m⁻¹ K⁻¹ were used to obtain the proposed method for the temperature range of 273–390 K and the pressure range of 100–20,000 kPa. In addition, the molecular mass M and structure of molecules, represented by the number of well-defined groups forming the molecule, were provided as input parameters in order to characterize the different molecules of ionic liquids. A heterogeneous set of ionic liquids includes cations such as imidazolium, ammonium, phosphonium, pyrrolidinium, and pyridinium. It also includes anions such as halides, sulfonates, tosylates, imides, borates, phosphates, acetates, and amino acids. The whole dataset was divided into a training set with 300 experimental data points and a prediction set with 100 experimental data points. Several architectures were studied, and the optimum weights for the network were determined. The results showed that the proposed method to estimate the thermal conductivity of ionic liquids at different temperatures and pressures presented a good accuracy with lower deviations such as AARD less than 0.91% and R² of 0.9969 for the training set, and AARD less than 0.84% with R² of 0.9963 for the prediction set.     

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...     

不同离子液体双水相萃取钯

为实现贵金属钯的绿色、高效萃取,本文使用有“绿色溶剂”之称的离子液体与磷酸钾形成的双水相体系,不加入其它萃取剂对钯(Ⅱ)进行萃取,并采用浊点法对所研究的6种咪唑类离子液体的双结线和系线进行测定。 结果表明,基于氯离子和溴离子的离子液体成相能力和萃取率无显著差异。 阳离子上支链的疏水性是影响咪唑类离子液体成相能力的关键因素之一。 与不含官能团的离子液体相比,支链上嵌入氨基和腈基的离子液体,成相能力较低,但萃取率分别提高了11.57%和34.26%。 当含腈基的离子液体浓度和磷酸钾浓度分别为5.00%和39.55%时,离子液体双水相体系对钯(Ⅱ)的萃取率可达到100%。 本文的研究成果为设计/选择可利用其双水相体系高效萃取钯(Ⅱ)的离子液体提供了理论基础和数据支持。     

环境友好型离子液体催化环氧丙烷反应合成丙二醇醚

丙二醇醚类化合物是性能优良的精细化学品,也是环保型高级溶剂.该类化合物具有两个强溶解性功能基团—醚键和羟基,前者具有亲油性,可溶解疏水性物质,后者具有亲水性,可溶解亲水性物质,因而丙二醇醚具有很强的溶解能力,素有"万能溶剂"之称,可广泛应用于涂料、油墨、油漆、印刷、电子化学品、染料、净洗和纺织等行业.丙二醇醚类化合物目前主要由环氧丙烷和低级脂肪醇反应合成,然而,由于环氧丙烷的位阻效应,使其在酸或碱的条件下开环的位置会不同,从而得到不同的醇醚产物.由于碱催化的醇醚产物更加环境友好,因而越来越被人们所关注.工业上丙二醇醚合成多采用传统的强碱性催化剂醇钠以及氢氧化钠,腐蚀性强,产生的废液量大.本文采用环境友好的非卤素离子液体作为催化剂,研究了其催化环氧丙烷醚化合成丙二醇醚的反应特性.本文采用两步法合成了一系列环境友好的醋酸类碱性功能化离子液体,并在温和的条件下将其用于催化环氧丙烷与醇反应合成丙二醇醚.结果表明,该类离子液体可以高效催化该反应的进行.利用紫外-可见光谱测定Hammett指数来表征实验中所用离子液体的碱强度,并构建了离子液体碱性与催化活性之间的关系.结果表明,离子液体的催化性能和其碱性密切相关,随着离子液体碱性的增加,催化活性增强,其中咪唑醋酸类离子液体碱性强于季胺类,表现出优异的催化性能.离子液体的碱性明显弱于NaOH,但却呈现出更优异的催化性能.相同反应条件下,EmimOAc离子液体作为催化剂,PO的转化率分别较NaOH高出20%–30%,选择性略高于NaOH,这可能是由于二者催化机理不同造成的.传统NaOH催化机理的关键步骤是醇在碱性催化剂的作用下去质子化形成电子供体烷氧根离子,促进环氧丙烷的开环加成.而本文提出了离子液体亲电亲核双活化作用机理,即离子液体在阴阳离子之间的氢键和电荷相互作用的共同作用下,促进环氧丙烷开环和醇的去质子化,形成相应的反应中间体.通过电喷雾质谱分析手段检测到了阴阳离子通过协同作用亲电亲核催化过程中的反应中间体,证明了该假设机理的可行性.此外,还考察了催化剂浓度、醇比、反应温度以及醇的空间位阻效应对反应的影响.以EmimOAc催化合成丙二醇丁醚为例,反应的转化率随催化剂浓度的增加而增大,在催化剂添加量1%(催化剂与PO的摩尔比)时,PO转化率达到最大值为98.2%,1-丁氧基-2-丙醇的选择性为86.4%.当正丁醇与环氧丙烷的摩尔比为3时,转化率最高为88.6%,选择性高达94%.该反应为放热反应,最适反应温度约为140 oC,此时转化率高达96.5%.在环氧丙烷和不同的低碳醇合成丙二醇醚的反应中,反应物醇的碳链越短,支链越少,催化反应效率越高.     

Surface tension and refractive index of pure and water-saturated tetradecyltrihexylphosphonium-based ionic liquids

Experimental data on the surface tension and refractive index of tetradecyltrihexylphosphonium-based ionic liquids with bromide, chloride, decanoate, methanesulfonate, dicyanimide, bis(2,4,4-trimethylpentyl)phosphinate and bis(trifluoromethylsulfonyl)imide anions are reported. The data were obtained for pure and water saturated samples at temperatures from 283 K to 353 K and at atmospheric pressure. The refractive index of the investigated ionic liquids decreases with increasing the water content in the sample. On the other hand, no clearly dependence of the surface tension with the water content up to a weight fraction of 16% was found. The prediction of the refractive index for the studied ionic liquids was also accomplished by a group contribution method and new values for the cation and diverse anions were estimated and proposed. The studied ionic liquids show lower surface tension in comparison with imidazolium-, pyridinium- or pyrrolidinium-based ionic liquids with a similar anion; also they show higher surface entropy than cyclic nitrogen-based fluids which indicates a lower surface organization. The anion dependence of the surface tension and surface entropy for the investigated ionic liquids is weaker than that for short-chain imidazolium-based ionic liquids. Their critical temperatures evaluated from Eötvos and Guggenheim equations are also lower than those of N-heterocyclic ionic fluids.     

Thermodynamic modeling of CO2 solubility in ionic liquid with heterosegmented statistical associating fluid theory

Heterosegmented statistical associating fluid theory is used to represent the CO₂ solubility in ionic liquids. As in our previous work, ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modeled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modeled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate. Carbon dioxide is modeled as a molecule with three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other. The parameters of CO₂ are obtained from the fitting of the density and the saturation vapor pressure of CO₂. For the CO₂-ionic liquid systems, cross association between site of type C in CO₂ and another association site in anion is allowed to occur to account for the Lewis acid–base interaction. The parameters for cross association interactions and the binary interaction parameters used to adjust the dispersive interactions between unlike segments are obtained from the fitting of the available CO₂ solubility in ionic liquids. The model is found to well represent the CO₂ solubility in the imidazolium ionic liquids from 283 to 415 K and up to 200 bar.     

离子液体固定化材料在固相萃取中的应用研究进展

离子液体是由阴、阳离子组成的低温熔融盐,几乎没有蒸汽压,具有稳定性好、溶解能力强、结构可设计、导电性好等优良性能.离子液体作为一种广受关注的新型“绿色溶剂”,具有代替传统有机溶剂的潜力,其制备方法和应用范围研究日趋完善和多样,已广泛应用于催化化学、光电化学、材料化学和分析化学等领域.离子液体通过功能化导向设计后,可以将...     

Effect of alkylimidazolium based ionic liquids on the structure of UV-irradiated cellulose

In this paper, the influence of three alkylimidazolium-based ionic liquids with the same cation (1-ethyl-3-methylimidazolium) and different anions (chloride, tetrafluoroborate and hexafluorophosphate) on the structure and properties of cellulose, have been studied by using Fourier transform infrared spectroscopy measurements, fluorescence microscopy imaging, viscometric and methylene blue sorption tests. Cellulose treated with ionic liquids showed better stability to UV light, as demonstrated by the lower variations of the polymerization degree, carboxyl groups content, moisture index, crystallinity index, lateral order index and allomorph index, with the increase of the UV exposure period, by comparing to non-treated cellulose. The results show that the tested ionic liquids could be effective as “green” plasticizers and UV stabilizers for cellulose-based materials.     

离子液体[emim]Br熔点的分子动力学模拟

运用分子动力学模拟, 采用直接加热法和微正则(NVE)系综法计算离子液体[emim]Br的熔点, 以期获得较好的熔点预测方法. 直接加热法通过分析体系的非键合能、密度、径向分布函数、扩散系数和平动序参数随温度的变化关系判断熔点; NVE系综法则通过获得固液共存体系判断熔点. 直接加热法中, 体系易出现过热问题; NVE系综法则能有效克服过热问题, 是在模拟研究中应优先选择的离子液体熔点预测方法.     

Tail aggregation and domain diffusion in ionic liquids

An extended multiscale coarse-graining model for ionic liquids is used to investigate the liquid crystal-like phase in certain ionic liquids. The tail groups of the cations with a sufficient side-chain length are found to aggregate, forming spatially heterogeneous domains, due to the competition between the electrostatic interactions between the charged head groups and the anions and the collective short-range interactions between the neutral tail groups. With a sufficiently long alkyl chain at a low enough temperature, the tail domains remain relatively stable, despite the diffusion of individual ions in the liquid phase. With increasing temperature, the average tail domains begin to diffuse, while beyond a transition temperature, their average density has an almost uniform distribution, although the tail groups still form instantaneous domains.     

Crystallisation kinetics of some archetypal ionic liquids: isothermal and non-isothermal determination of the Avrami exponent

The properties of ionic liquids give rise to applications in diverse technology areas including mechanical engineering, mining, aerospace and defence. The arbitrary physical property that defines an ionic liquid is a melting point below 100 °C, and as such, an understanding of crystallisation phenomena is extremely important. This is the first report dealing with the mechanism of crystallisation in ionic liquids. Assuming crystallisation of the ionic liquids is a thermal or mass diffusion-controlled process, the values of the isothermal Avrami exponent obtained from three different ionic liquids with three different anions and cations all indicate that growth occurs with a decreasing nucleation rate (n=1.8-2.2). For one of the ionic liquids it was possible to avoid crystallisation by fast cooling and then observe a devitrification upon heating through the glass transition. The isothermal Avrami exponent of devitrification suggested growth with an increasing nucleating rate (n=4.1), compared to a decreasing nucleation rate when crystallisation occurs on cooling from the melt (n=2.0). Two non-isothermal methods were employed to determine the Avrami exponent of devitrification. Both non-isothermal Avrami exponents were in agreement with the isothermal case (n=4.0-4.15). The applicability of JMAK theory suggests that the nucleation event in the ionic liquids selected is a random stochastic process in the volume of the material. Agreement between the isothermal and non-isothermal techniques for determining the Avrami exponent of devitrification suggests that the pre-exponential factor and the activation energy are independent of thermal history. The heating rate dependence of the glass transition enabled the calculation of the fragility index, which suggests that the ionic liquid is a "strong" glass former. This suggests that the temperature dependence of the rate constant could be close to Arrhenius, as assumed by JMAK theory. More generally, therefore, it can be concluded that there is nothing unusual about the crystallisation mechanism of the ionic liquids studied here.     

醇类化合物气相色谱保留指数的分子拓扑研究

分子中原子i的特征值(ti)定义为tj＝1 ∑hi。并计算了醇类化合物的氢连接性指数，藉助多元线性回归技术分别建立了25个醇类化合物的指数与这些物质的气相色谱保留指数的定量结构／性质相关关系模型。模型具有良好的稳定性和预测能力，氢连接性指数能较好地反映化合物的结构特征。     

Preparation of Nanoparticles and Diffusion Behavior of Metal Ions in Ionic Liquids

Ionic liquids (ILs) have attracted much attention as tunable liquids because of their unique structures and properties. However, the mechanisms of chemical reactions and solute diffusion in ionic liquids are still unknown. This article summarizes our previous studies and recent results on the mechanisms of metal particle formation and solute diffusion in ionic liquids, focusing on the local structure of ionic liquids. It was found that the shape and size of metal particles formed in ionic liquids using electron beams or X-rays are strongly influenced by the local structure. In the study of the diffusion behavior of metal ions in ionic liquids, we proposed a hopping-like diffusion model and proposed that this behavior could be strongly influenced by local structures such as hole concentration and/or domain structures.     

胍盐离子液体捕获CO2温室气体的机理

通过量子力学与分子动力学对胍盐离子液体的模拟表明,胍阳离子与氯负离子之间存在较强的相互作用,其相互作用能约为-109．216kcal／m01．从能量与几何分布可见,两种空间分布方式中最稳定构象为Middle作用模式．径向分布函数也验证了这一结论．C02含量的不断增加并没有对离子液体的结构产生影响,而是被离子液体的空腔捕获．     

Picosecond time-resolved fluorescence study on solute-solvent interaction of 2-aminoquinoline in room-temperature ionic liquids: aromaticity of imidazolium-based ionic liquids

Time-resolved fluorescence spectra and fluorescence anisotropy decay of 2-aminoquinoline (2AQ) have been measured in eight room-temperature ionic liquids, including five imidazolium-based aromatic ionic liquids and three nonaromatic ionic liquids. The same experiments have also been carried out in several ordinary molecular liquids for comparison. The observed time-resolved fluorescence spectra indicate the formation of pi-pi aromatic complexes of 2AQ in some of the aromatic ionic liquids but not in the nonaromatic ionic liquids. The fluorescence anisotropy decay data show unusually slow rotational diffusion of 2AQ in the aromatic ionic liquids, suggesting the formation of solute-solvent complexes. The probe 2AQ molecule is likely to be incorporated in the possible local structure of ionic liquids, and hence the anisotropy decays only through the rotation of the whole local structure, making the apparent rotational diffusion of 2AQ slow. The rotational diffusion time decreases rapidly by adding a small amount of acetonitrile to the solution. This observation is interpreted in terms of the local structure formation in the aromatic ionic liquids and its destruction by acetonitrile. No unusual behavior upon addition of acetonitrile has been found for the nonaromatic ionic liquids. It is argued that the aromaticity of the imidazolium cation plays a key role in the local structure formation in imidazolium-based ionic liquids.     

Matrix-assisted laser desorption/ionization mass spectrometry for the characterization of ionic liquids and the analysis of amino acids, peptides and proteins in ionic liquids

Ionic liquids are interesting solvents for a number of applications in chemistry and biotechnology. We characterized five different ionic liquids by laser desorption/ionization (LDI) and by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) and studied the analysis of amino acids, peptides and proteins dissolved in these solvents. Signals of both anions and cations of the ionic liquids could be observed both in LDI- and in MALDI-MS. In the latter case, adduct formation between anions and cations of the analytes was observed. Amino acids, peptides and proteins could be analyzed in ionic liquids after addition of matrix substances. Sodium and potassium adducts were not observed in any analysis involving ionic liquids. Low molecular mass compounds and peptides could be analyzed best in the presence of water-immiscible ionic liquids, whereas proteins gave the best results in water-miscible ionic liquids. Optimal analysis conditions such as molar matrix-to-analyte and ionic liquid-to-matrix ratios were determined. Homogeneity of samples in the presence of ionic liquids was reduced compared with classical MALDI preparations. Relative quantitation of amino acids was possible using isotope-labeled internal standards. MALDI-MS thus can be used for the analysis of chemical reactions and the screening of enzyme-catalyzed reactions in ionic liquids and for the analysis of the biocatalysts dissolved in these solvents. Theoretical aspects of ion formation in the presence of ionic liquids both in LDI and MALDI analysis are discussed.     

离子液体的定量结构-性质/活性研究

本文系统介绍了离子液体定量结构-性质/活性相关(QSPR/QSAR)的研究方法和步骤,综述了QSPR/QSAR在离子液体的熔点、有机物在离子液体中的无限稀释活度系数、离子液体的表面张力、离子液体的电导率、有机物在离子液体中的溶解度、离子液体的黏度以及离子液体的生物毒性和降解性等方面的最新研究进展,总结了该方法的优缺点,并对未来的研究趋势进行了展望。     

Eutectic-based ionic liquids with metal-containing anions and cations

Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids. FAB-MS analysis shows that the liquids are made up of metal-containing anions and cations in which the donor is coordinated to the cation. Data on the viscosity, conductivity, density, phase behaviour and surface tension are presented and these are shown to be significantly different to other related ionic liquids that incorporate quaternary ammonium salts. The conductivity and viscosity are comparable with other ionic liquids and the data fit well to the Hole theory model recently proposed.