用核磁共振技术研究[C4mim][BF4]在重水和氘代氯仿中的聚集行为

运用核磁共振技术, 研究了室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐([C4mim][BF4])在重水和氘代氯仿中的聚集行为. 实验结果表明, 随着混合体系中离子液体摩尔分数的增加, 在重水中, 离子液体阳离子上各氢原子的化学位移向低场移动, 且呈现了先急剧变化, 后趋于平缓的变化趋势; 在氘代氯仿中, 离子液体阳离子上H2的化学位移向高场移动, H4和H5以及与氮原子直接相连的甲基和亚甲基上的氢原子的化学位移都向低场移动, 且各氢原子的核磁共振信号发生了变化. 根据质量作用定律及1H NMR化学位移随浓度的变化关系计算了[C4mim][BF4]在重水中的临界聚集浓度和聚集数, 并在离子液体阴、阳离子缔合以及离子液体与溶剂相互作用的基础上对实验结果进行了讨论.     

甘氨酸离子液体[C3mim][Gly]和[C4mim][Gly]水溶液的表面张力

本文用中和法合成了基于烷基咪唑的甘氨酸离子液体[C3mim][Gly]（1-丙基-3-甲基咪唑甘氨酸离子液体）和[c4miml[Gly]（1-丁基-3．甲基咪唑甘氨酸离子液体）,在298．15K下,0．0400-0．5000molkg^-1浓度范围内测定了不同浓度[C4mim][Oly]和[c3mim][Gly]离子液体水溶液的密度和表面张力,得到了溶液等张比容的实验值,提出了预测不同浓度溶液等张比容的经验方程,利用这个经验方程和李以圭等人提出的溶液表面张力模型,分别估算了这两种离子液体水溶液的表面张力,其估算值和实验值在误差范围内很好地吻合．     

[C4mim][PF6]和[C4mim][NTf2]离子液体辐射诱导的相行为及荧光行为变化

离子液体因其低挥发性, 高热稳定性及优良的萃取性能被认为是萃取分离放射性核素的新一代绿色溶剂, 而研究离子液体本身的辐射效应是其实际应用的重要前提. 本文以60Co为辐射源, 系统研究了γ辐照对两种常见的憎水性咪唑离子液体1-丁基-3-甲基咪唑六氟磷酸盐([C4mim][PF6])和1-丁基-3-甲基咪唑三氟甲基磺酰胺酸盐([C4mim][NTf2])的相行为及荧光行为的影响. 在相行为方面, γ辐照使离子液体的结晶驰豫时间增加, 导致其低温结晶延迟. 在荧光行为方面, γ辐照后离子液体的荧光光谱保持原有的“红边效应(red edge effect)”, 但随吸收剂量增加, 光谱整体发生红移(最大移动幅度达150 nm). 并且这种“红边效应”在辐照后离子液体的乙腈稀释剂中仍然存在, 且随稀释倍数增加光谱整体发生蓝移. [C4mim][PF6]和[C4mim][NTf2]离子液体辐照后的这种相行为及荧光行为的变化可归因于辐照对其阴阳离子空间相关性(缔合行为)的影响.     

[C_4mim][PF_6]和[C_4mim][NTf_2]离子液体辐射诱导的相行为及荧光行为变化

离子液体因其低挥发性,高热稳定性及优良的萃取性能被认为是萃取分离放射性核素的新一代绿色溶剂,而研究离子液体本身的辐射效应是其实际应用的重要前提.本文以~(60)Co为辐射源,系统研究了γ辐照对两种常见的憎水性咪唑离子液体1-丁基-3-甲基咪唑六氟磷酸盐([C_4mim][PF_6])和1-丁基-3-甲基咪唑三氟甲基磺酰胺酸盐([C_4mim][NTf_2])的相行为及荧光行为的影响.在相行为方面,γ辐照使离子液体的结晶驰豫时间增加,导致其低温结晶延迟.在荧光行为方面,γ辐照后离子液体的荧光光谱保持原有的"红边效应(red edge effect)",但随吸收剂量增加,光谱整体发生红移(最大移动幅度达150 nm).并且这种"红边效应"在辐照后离子液体的乙腈稀释剂中仍然存在,且随稀释倍数增加光谱整体发生蓝移.[C_4mim][PF_6]和[C_4mim][NTf_2]离子液体辐照后的这种相行为及荧光行为的变化可归因于辐照对其阴阳离子空间相关性(缔合行为)的影响.     

丙氨酸离子液体[C4mim][Ala]的热化学性质

在298.15 K下利用恒温环境溶解热量计测定了一系列含有已知微量水的1-丁基-3-甲基咪唑丙氨酸盐([C₄mim][Ala])离子液体(IL)不同浓度样品的摩尔溶解焓. 借助Debye-Hückel极限项, 用外推法确定了不同含水量的[C₄mim][Ala]样品的标准摩尔溶解焓[Δ_sH_m⁰(wc)]. 随着样品中水含量的增加, Δ_sH_m⁰(wc)的绝对值下降, 将Δ_sH_m⁰(wc)对含水量作图得到很好的直线, 其截距Δ_sH_m⁰(pure IL)=-60.74 kJ/mol, 可看作是不含水的[C₄mim][Ala]标准摩尔溶解焓的估算值. 利用精密氧弹热量计测定了[C₄mim][Ala]的燃烧热, 计算得到其标准摩尔生成焓Δ_fH_m⁰=(-675±11) kJ/mol.     

过渡金属离子液体[C2mim][FeCl4]的溶解热

在干燥氩气氛下, 用等摩尔的高纯无水FeCl3和氯化1-甲基-3-乙基咪唑([C2mim][Cl])直接搅拌混合, 制备棕色透明的含过渡金属铁的离子液体[C2mim][FeCl4]. 在298.15 K下, 利用具有恒温环境的溶解反应热量计测定了这种离子液体的摩尔溶解焓(ΔsHm). 针对[C2mim][FeCl4]溶解于水后即分解的特点, 在Pitzer电解质溶液理论基础上, 提出了确定这种离子液体标准摩尔溶解焓的新方法, 得到了[C2mim][FeCl4]的标准摩尔溶解焓(ΔsH 0—m=-76.6 kJ/mol), 以及Pitzer焓参数组合: β(0)LFe,Cl+β(0)L[C2mim], Cl+ΦLFe,[C2mim]=0.072209和β(1)LFe,Cl+β(1)L[C2mim], Cl=0.15527. 借助热力学循环和Glasser离子液体晶格能理论, 用Fe3+, Cl-和[C2mim]+的离子水化焓数据以及[C2mim][FeCl4]标准摩尔溶解焓, 估算得到了配离子[FeCl4]-(g)解离成Fe3+(g)和4Cl-(g)的解离焓为5659 kJ/mol. 这个结果揭示了离子液体[C2mim][FeCl4]的标准摩尔溶解焓绝对值并不很大的原因, 即很大的离子水化焓被很大的[FeCl4]-(g)的解离焓相互抵消.     

离子液体[C2mim][GaCl4]的溶解热研究

在干燥氩气氛下, 用等摩尔的高纯无水GaCl3和[C2mim][Cl](氯化1-甲基-3-乙基咪唑)直接搅拌混合, 制备了淡黄色透明的的离子液体[C2mim][GaCl4] (1-ethyl-3-methylimidazolium chlorogallate) . 在298.15 K下, 利用具有恒温环境的溶解反应热量计, 测定了这种离子液体的不同浓度摩尔溶解焓 . 针对[C2mim][GaCl4]溶解于水后即分解的特点, 在Pitzer电解质溶液理论基础上, 提出了确定这种离子液体标准摩尔溶解焓的新方法, 得到了[C2mim][GaCl4]在水中的标准摩尔溶解焓, ＝－132 kJ•mol－1, 以及Pitzer焓参数组合: ＝－0.1373076和 ＝0.3484209. 借助热力学循环和Glasser离子液体晶格能理论, 用Ga3＋, Cl－和[C2mim]—的离子水化焓数据以及本文得到的[C2mim][GaCl4]标准摩尔溶解焓, 估算了配离子4Cl－(g)解离成Ga3＋(g)和4Cl－(g)的解离焓ΔHdis([GaCl4]-)≈5855 kJ•mol－1. 这个结果揭示了离子液体[C2mim][GaCl4]的标准摩尔溶解焓绝对值并不很大的原因, 即是很大的离子水化焓被很大的[GaCl4]－(g)的解离焓相互抵消了.     

气态二聚体[C1~6mim]2[BF4]2纳米微观结构的理论研究

在B3LYP/6-311+G(d,p)的水平上采用密度泛函理论研究了[C_nmim]+(n=1~6)与[BF_4]~ˉ形成二聚体[C_nmim]_2[BF_4]_2(n=1~6)的微观纳米结构。通过理论计算二聚体的相互作用能量发现,阴阳离子之间存在较强的氢键作用,且随着咪唑鎓烷基链的增加相互作用能也随之增加,另外,烷基侧链的长度会影响氢键强度。当咪唑鎓烷基侧链中C的个数大于4时,烷基尾部能够发生聚合,从而形成类胶束纳米结构。通过对自然布居分析、自然键轨道以及弱相互作用的分析和计算,同样证明了二聚体中存在较强的氢键作用,烷基侧链中碳的个数影响了离子液体的微观结构。     

室温离子液体[bmim][BF4]和水混合物的计算机模拟研究

针对室温离子液体[bmim][BF₄]和水的混合物, 用分子动力学模拟研究了溶液的微观组成与浓度的关系. 模拟结果表明：该混合物中各组分间的径向分布函数随[bmim][BF₄]摩尔分数的增加呈有规律的变化；在此基础上计算了溶液的局部组成以及组分间的缔合因子, 进一步考察了各组分间的相互作用情况；另外基于Kirkwood-Buff理论估算了混合物的偏摩尔体积、等温压缩因子以及活度系数对浓度的偏导数, 对于理解离子液体与水之间的交互作用具有一定的参考意义.     

[C3mim][NTf2]/DEC/[Li][NTf2]体系的基础性质

The hydrophobic ionic liquid (IL) 1-propyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C₃mim][NTf₂]) was synthesized according to traditional methods. By adding different amounts of diethyl carbonate (DEC) solvent and lithium bis[(trifluoromethyl)sulfonyl]imide ([Li][NTf₂]) salt to [C₃mim][NTf₂] IL, eight solution systems were prepared. First, the thermodynamic properties of the eight solution systems were characterized by differential scanning calorimetry (DSC). The semi-stable temperature of the system gradually disappeared with increasing lithium salt content, but the melting point temperature was not apparent in the experiment. These results indicate that DEC and lithium salts can dissolve in ILs within the tested temperature range. The basic properties of the eight systems, including thermodynamic and dynamic properties, were systematically studied at different temperatures. The variation in the self-diffusion coefficient of lithium ion ([Li]⁺) as a function of DEC concentration, density changes, viscosity, conductivity, and the viscosity/conductivity activation energy of the eight systems was calculated by the Vogel Fulcher Taman (VFT), Final Vogel Fulcher Taman (FVFT), and Arrhenius equations. The effect of temperature on the properties of the system was studied in detail. Within the temperature range measured herein, the deviation between the fitting equation and experimental value was small. Consequently, these equations were successfully used to calculate the properties of the system at various temperatures. All fitting parameters of the corresponding equations are provided herein. The viscosity for all systems decreased rapidly with increasing temperature, which increased the conductivity. Based on these experiments, the influence of DEC on the system microstructure was discussed in the context of the molecular dynamics simulation results. In particular, the interaction between [Li]⁺ and [NTf₂]^-/DEC was examined. In all solution systems, [NTf₂]^- coordinates to [Li]⁺ through only the O atom and not the N atom. Radial distribution function (RDF) analysis showed that the interaction between [Li]⁺ and [NTf₂]^- weakened with increasing DEC concentration. DEC molecules were observed in the first solvation layer of [Li]⁺ coordinating to [Li]⁺ through the carbonyl O atom. Although the interaction between [Li]⁺ and DEC was weakened, competition between [NTf₂]^- and DEC in the first solvation layer of [Li]⁺ was observed by the coordination number analysis of the O atom around [Li]⁺. Therefore, the introduction of DEC is beneficial for Li⁺ diffusion, which is consistent with the experimental results.     

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.     

Thermomorphic Behavior of the Ionic Liquids [C4mim][FeCl4] and [C12mim][FeCl4]

The iron‐containing ionic liquids 1‐butyl‐3‐methylimidazolium tetrachloroferrate(III) [C₄mim][FeCl₄] and 1‐dodecyl‐3‐methylimidazolium tetrachloroferrate(III) [C₁₂mim][FeCl₄] exhibit a thermally induced demixing with water (thermomorphism). The phase separation temperature varies with IL weight fraction in water and can be tuned between 100 °C and room temperature. The reversible lower critical solution temperature (LCST) is only observed at IL weight fractions below ca. 35 % in water. UV/Vis, IR, and Raman spectroscopy along with elemental analysis prove that the yellow‐brown liquid phase recovered after phase separation is the starting IL [C₄mim][FeCl₄] and [C₁₂mim][FeCl₄], respectively. Photometry and ICP‐OES show that about 40 % of iron remains in the water phase upon phase separation. Although the process is thus not very efficient at the moment, the current approach is the first example of an LCST behavior of a metal‐containing IL and therefore, although still inefficient, a prototype for catalyst removal or metal extraction.     

离子液体四氟硼酸-1-戊基-3-甲基咪唑的物理化学性质的估算

根据标准加入法原理配制一系列含有已知微量水的离子液体四氟硼酸-1-戊基-3-甲基咪唑([C5mim][BF4])样品,在278.15～338.15 K温度范围内,样品的密度与其含水量呈很好线性关系. 利用外推方法确定了含水量为零时[C5mim][BF4]的密度ρ,得到了密度随温度变化的经验方程:ln ρ=0.120 11-5.79×10-4(T-298.15)和离子液体的热膨胀系数α=5.79×10-4K-1. 根据Glasser理论估算了[C5mim][BF4]的标准熵、表面能和晶格能,晶格能较小使离子液体在室温下能以液态形式存在. 利用空隙模型计算得到了[C5mim][BF4] 热膨胀系数α(计算),与实验测定值在数量级上一致,说明空隙模型有一定的合理性.     

The surface tension,density and refractive index of amino acid ionic liquids: [C3mim][Gly] and [C4mim][Gly]

The amino acid ionic liquids (AAILs) [C₃mim][Gly] (1-propyl-3-methylimidazolium glycine) and [C₄mim][Gly] (1-butyl-3-methylimidazolium glycine) have been prepared by the neutralization method and characterized by ¹H NMR spectroscopy and differential scanning calorimetry (DSC). The values of their density, surface tension and refractive index were measured at different temperatures. Since the AAILs can form strong hydrogen bonds with water, small amounts of water are difficult to remove from the AAILs by common methods. In order to eliminate the effect of the impurity as water, the standard addition method (SAM) was applied to these measurements. The values of thermal expansion coefficients, α, surface excess energy, E_a, surface excess entropy, S_a, and molar refraction, R_m, for the AAILs were determined.     

Densities and viscosities for ionic liquids mixtures containing [eOHmim][BF4], [bmim][BF4] and [bpy][BF4]

Densities and viscosities of binary ionic liquids mixtures, 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) were measured over the entire mole fraction from T = (298.15 to 343.15) K. The excess molar volumes were calculated and correlated by Redlich–Kiser polynomial expansions. The viscosities for pure ionic liquids were analyzed by means of the Vogel–Tammann–Fulcher equation and ideal mixing rules were applied for the ILs mixtures.     

1-甲基-3-乙基咪唑缬氨酸盐离子液体[C2mim][Val]的热化学

用中和法合成了氨基酸离子液体1-甲基-3-乙基咪唑缬氨酸盐([CB_2Bmim][Val]). 在298.15±0.01 K下, 利用恒温溶解反应热量计测定了不同含水量的[CB_2Bmim][Val]溶解成不同质量摩尔浓度溶液的溶解焓, ΔB_solBHB_mB (w), 借助标准加入法(SAM)和Archer方法得到了无水离子液体[CB_2Bmim][Val]的标准摩尔溶解焓, . 利用RB-II型精密转动弹热量计测定了该离子液体的燃烧热, 计算了其标准摩尔燃烧焓 和标准摩尔生成焓 |并结合该离子液体的标准摩尔溶解焓和乙基咪唑阳离子[CB_2Bmim]^＋在水溶液中的标准摩尔生成焓, 计算了[Val]P^－离子在水溶液中的标准摩尔生成焓. 利用RD496-III型热导式微量热量计测定了不同质量摩尔浓度[CB_2Bmim][Val]水溶液的稀释焓, 根据扩展的Debye-Hückel方程计算得到的相对表观摩尔焓P^φPL和根据Pitzer离子相互作用模型的计算值在实验误差范围内很好一致.