Special Mixing Behavior of Chelate-based Ionic Liquid with Methanol

Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) ([C₁₀mim][Cu(hfacac)₃]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate ([C₁₀mim][hfacac]) blue-shifted more significantly than that of [C₁₀mim][Cu(hfacac)₃], meanwhile the (C=O) red-shifted in [C₁₀mim][Cu(hfacac)₃], which is contrast with that in [C₁₀mim][hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in [C₁₀mim][hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the [C₁₀mim][Cu(hfacac)₃] system.     

Flexo-Ionic Effect of Ionic Liquid Crystal Elastomers

The first study of the flexo-ionic effect, i.e., mechanical deformation-induced electric signal, of the recently discovered ionic liquid crystal elastomers (iLCEs) is reported. The measured flexo-ionic coefficients were found to strongly depend on the director alignment of the iLCE films and can be over 200 µC/m. This value is orders of magnitude higher than the flexo-electric coefficient found in insulating liquid crystals and is comparable to the well-developed ionic polymers (iEAPs). The shortest response times, i.e., the largest bandwidth of the flexo-ionic responses, is achieved in planar alignment, when the director is uniformly parallel to the substrates. These results render high potential for iLCE-based devices for applications in sensors and wearable micropower generators.     

Aggregation Behavior of Trisiloxane-Tailed Surface Active Ionic Liquids in Aqueous Solution: Coarse-Grained Molecular Dynamics Study

The aggregation behaviors of two trisiloxane-tailed surface active ionic liquids in water have been investigated by coarse-grained (CG) molecular dynamics simulation on the basis of MARTINI force field. The new CG model is developed from the optimized molecule computed by using density functional theory. Direct comparison of angles and bonds obtained from all-atom (AA) simulations with those calculated from the CG model has been conducted to validate the latter model. Excellent agreement between AA and CG demonstrates that the potential of the new CG model can represent the complex system well. The long time CG simulation has been performed to understand the formation process of micelles when dissolving ionic liquids in water. Vesicles were observed at the final stage of the simulation and their partially truncated views and density profiles were obtained to describe the structure in detail.     

Nanostructuration Effect on the Thermal Behavior of Ionic Liquids

This work shows how the nanostructuration of ionic liquids (ILs) governs the glass and melting transitions of the bistriflimide imidazolium‐based [C_nC₁im][NTf₂] and [C_nC_nim][NTf₂] series, which highlights the trend shift that occurs at the critical alkyl size (CAS) of n=6. An initial increase in the glass temperature (T_g) with an increase in the alkyl side chain was observed due to the intensification of the dispersive interactions (van der Waals). Above the CAS, the ?CH₂? increment has the same effect in both glass and liquid states, which leads to a plateau in the glass transition after nanostructuration. The melting temperature (T_m) of the [C_nC₁im][NTf₂] and [C_nC_nim][NTf₂] series presents a V‐shaped profile. For the short‐alkyl ILs, the ?CH₂? increment affects the electrostatic ion pair interactions, which leads to an increase in the conformational entropy. The ?CH₂? increment disturbs the packing ability of the ILs and leads to a higher entropy value ( ) and consequently a decrease in T_m. Above the CAS, the ?CH₂? contribution to the melting temperature becomes more regular, as a consequence of the nanostructuration of the IL into polar and nonpolar domains. The dependence of the alkyl chain on the temperature, enthalpy, and entropy of melting in the ILs above the CAS is very similar to the one observed for the alkane series, which highlights the importance of the nonpolar alkyl domains on the ILs thermal behavior.     

Modulating the Solubilities of Ionic Liquid Components in Aqueous–Ionic Liquid Biphasic Systems: A Q‐NMR Investigation

Aqueous–ionic liquid (A–IL) biphasic systems have been examined in terms of deuterated water, acid, and IL cation and anion mutual solubilities in the upper (water‐rich, in mole fraction) and lower phase of aqueous/IL biphasic systems at ambient temperature. The biphasic mixtures were composed of deuterated acids of various concentrations (mainly DCl, DNO₃, and DClO₄ from 10^?2 to 10^?4 M ) and five ionic liquids of the imidazolium family with a hydrophobic anion (CF₃SO₂)₂N^?, that is, [C₁C_nim][Tf₂N], (n=2, 4, 6, 8 and 10). The analytical techniques applied were ¹H NMR, ¹⁹F NMR, Karl–Fischer titration, pH potentiometry for IL cations and anions, and water and acid determination. The effects of the ionic strength (μ=0.1 M NaCl and NaNO₃ as well as μ=0.1 M , 0.2 M and 0.4 M NaClO₄, according to the investigated acid), the nature of the IL cation, and the nature of the mineral acid on the solubilities of the (D₂O, D⁺, Tf₂N^?, C₁C_nim⁺) entities in the lower or upper phases were determined. The addition of sodium perchlorate was found to enhance the Tf₂N^? solubility while inhibiting the solubility of the ionic liquid cation. Differences in IL cation and anion solubilities of up to 42 mM were evidenced. The consequences for the characterization of the aqueous biphasic system, the solvent extraction process of the metal ions, and the ecological impact of the ILs are discussed.     

Azolate Anions in Ionic Liquids: Promising and Under-Utilized Components of the Ionic Liquid Toolbox

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations (i.e., [C_nmim]⁺) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron-withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate-containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials.     

α‐Fe2O3 Cubes with High Visible‐Light‐Activated Photoelectrochemical Activity towards Glucose: Hydrothermal Synthesis Assisted by a Hydrophobic Ionic Liquid

A liquid/liquid interfacial reaction system was designed to fabricate α‐Fe₂O₃ cubes. The reaction system uses a hydrophobic ionic liquid containing iron ions ([(C₈H₁₇)₂(CH₃)₂N]FeCl₄) for manufacturing α‐Fe₂O₃ cubes by a novel and environmentally friendly hydrothermal method under low‐temperature conditions (140 °C). The iron‐containing ionic liquid is hydrophobic and can form a liquid/liquid interface with water, which is vital for fabrication of the α‐Fe₂O₃ cubes. Nanomaterials synthesized from hydrophobic iron‐containing ionic liquids show good crystallinity, well‐developed morphology, and uniform size. The effect of different ionic liquids on the morphology of α‐Fe₂O₃ was investigated in detail. [(C₈H₁₇)₂(CH₃)₂N]FeCl₄ is assumed to perform the triple role of forming a liquid/liquid interface with water and acting as reactant and template at the same time. The effect of the reaction temperature on the formation of the α‐Fe₂O₃ cubes was also studied. Temperatures lower or higher than 140 °C are not conducive to formation of the α‐Fe₂O₃ cubes. Their photoelectrochemical properties were tested by means of the transient photocurrent response of electrodes modified with as‐prepared α‐Fe₂O₃ cubes. The photocurrent response of an α‐Fe₂O₃ cubes/indium tin oxide electrode is high and stable, and it shows great promise as a photoelectrochemical glucose sensor with high sensitivity and fast response, which are beneficial to practical applications of nanosensors.     

百草枯在碳纳米管与离子液体复合修饰电极上的电化学行为及测定

制备了碳纳米管(MWCNTs)和疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸盐(BMIMPF6)复合修饰电极(MWCNTs-BMIMPF6/GCE),并采用红外光谱(IR)分别对MWCNTs、BMIMPF6及MWCNTs-BMIMPF6进行了表征。运用循环伏安法研究了百草枯(PQ)在该修饰电极上的电化学行为。结果表明,在pH7.0的PBS缓冲溶液中,PQ在MWCNTs-BMIMPF6/GCE上出现2对明显的氧化还原峰,在20~200 mV/s扫描速率范围内,其氧化还原峰电流均与扫描速率平方根(v1/2)呈线性关系,表明该电极过程受扩散控制。计算了电极过程的部分动力学参数:电极有效面积A=0.156 4 cm2,百草枯在pH7.0的PBS缓冲液中的扩散系数D=7.0×10-5cm2/s。优化了方波溶出伏安法(SWSV)的实验参数,发现峰电流Ipa1与PQ浓度在7.729×10-7~9.660×10-5mol/L范围内呈线性关系,检出限为1.576×10-7mol/L。采用该方法对实际水样进行检测,增敏回收率为93%~104%。     

The Effect of Fluorinated Solvents on the Physicochemical Properties,Ionic Association,and Free Volume of a Prototypical Solvate Ionic Liquid

Solvate ionic liquid (SIL) synthesis and properties depend on a delicate balancing of cation-solvent and cation-anion interactions to produce materials containing only cation-solvent complexes and solvent-separated anions. Most SILs meeting these characteristics fall within the paradigm of oligomeric ethylene oxides (e.g. glymes and glycols) and lithium salts. Targeted functionalization of solvent molecules to achieve desired properties is a relatively unexplored avenue of research. Fluorinated solvents have significantly different electric charge distributions compared to their nonfluorinated analogs. We test the impact of solvent fluorination for a SIL created from equimolar mixtures of lithium bis(trifluoromethylsulfonyl)imide (LiNTf₂) and triethylene glycol (TEG), hereafter [(TEG)₁Li]NTf₂. In the first experiment, TEG is partially substituted with 2,2,4,4,5,5,7,7-octafluoro-3,6-dioxaoctane-1,8-diol (FTEG). This leads to a precipitous decrease in ionic conductivity and larger quantities of ionically-associated Li(NTf₂)₂⁻ species, as detected with vibrational spectroscopy. These observations suggest FTEG does not readily coordinate Li⁺ ions in a manner analogous to TEG. Computational studies reinforce this conclusion. Relative complex cation stabilities are ranked as [(FTEG)₁Li]⁺>[(TEG)₁Li]⁺. A second experiment adds FTEG as a diluent to [(TEG)₁Li]NTf₂. This places FTEG and TEG in competition to coordinate a limited number of Li⁺ ions. The resulting mixtures exhibit conductivity enhancement over the parent SIL and minimal changes in ion speciation due to the poor Li⁺ binding by FTEG compared to TEG. Positron annihilation lifetime spectroscopic studies point to increased amounts of free volume upon dilution of FTEG. This likely explains the origin of the conductivity and viscosity enhancements.     

From Salts to Ionic Liquids by Systematic Structural Modifications: A Rational Approach Towards the Efficient Modular Synthesis of Enantiopure Imidazolium Salts

This paper reports a simple and robust modular synthetic strategy that leads to a large variety of configurationally and structurally diverse imidazole‐based chiral ionic liquids (CILs) by lipase‐catalyzed resolution. The intimate microscopic interactions of the supramolecular ionic network of these imidazolium chiral salts at the molecular level are investigated both spectroscopically (NMR, FT‐IR‐ATR) and theoretically, and a topological analysis of the experimental electron densities obtained by X‐ray dif fr action of single crystals is performed. Our results support the key role played by the relative configuration of the ‐OR group on the hydrogen‐bonding pattern and its strong influence on the final physical properties of the imidazolium salt. We also obtained a reasonable correlation between the observed melting point and the non‐covalent interactions. The spectroscopic data and the topological analysis reflect the key role played by hydrogen bonds between the OH and imidazolium C2H groups in both cation–anion and cation–cation interactions, with the presence of an OH group leading to an additional inter‐cation interaction. This interaction significantly affects the properties of stereoisomeric salts. Even more interestingly, we also studied the effect of the chirality by comparing enantiopure CILs with their racemic mixtures and found that, with the exception of trans‐Cy6‐OH‐Im‐Bn‐Br, the melting points of the racemic mixtures are higher than those of the corresponding enantiomerically pure forms. For stereoisomeric examples, we have successfully explained the differences in melting temperatures in light of the corresponding structural data. Chirality should therefore be taken into account as a highly attractive design vector in the preparation of ILs with specifically desired properties.     

离子液体修饰对Cu/USY催化乙炔氢氯化反应性能的影响

为了提高Cu/USY催化剂在乙炔氢氯化反应中的催化活性,设计并成功制备了一系列离子液体修饰的分子筛负载的铜基催化剂(Cu@TPPB/USY).当铜和TPPB的百分含量均为15时,在反应温度为160℃,乙炔气体空速为120 h-1,氯化氢与乙炔的摩尔比为1.25:1的条件下,催化剂的乙炔转化率提升了1.17倍,氯乙烯选择性一直保持在98%以上.结合催化剂的傅里叶红外(FT-IR)、 N2物理吸脱附(BET)、热重分析(TG)、 X射线光电子能谱(XPS)、透射电镜(TEM)、 X射线衍射(XRD)、氢气程序升温还原(H2-TPR)和等离子体发射光谱(ICP-OES)的表征,认为TPPB的修饰不仅可以促进催化剂中Cu物种的分散,抑制其还原和流失,还能减少催化剂表面积碳、增强Cu活性物种与载体间的相互作用力,有效地提高Cu/USY催化剂的催化活性.     

Quantum and Classical Molecular Dynamics of Ionic Liquid Electrolytes for Na/Li‐based Batteries: Molecular Origins of the Conductivity Behavior

Compositional effects on the charge‐transport properties of electrolytes for batteries based on room‐temperature ionic liquids (RTILs) are well‐known. However, further understanding is required about the molecular origins of these effects, in particular regarding the replacement of Li by Na. In this work, we investigate the use of RTILs in batteries, by means of both classical molecular dynamics (MD), which provides information about structure and molecular transport, and ab initio molecular dynamics (AIMD), which provides information about structure. The focus has been placed on the effect of adding either Na⁺ or Li⁺ to 1‐methyl‐1‐butyl‐pyrrolidinium [C₄PYR]⁺ bis(trifluoromethanesulfonyl)imide [Tf₂N]^?. Radial distribution functions show excellent agreement between MD and AIMD, which ensures the validity of the force fields used in the MD. This is corroborated by the MD results for the density, the diffusion coefficients, and the total conductivity of the electrolytes, which reproduce remarkably well the experimental observations for all studied Na/Li concentrations. By extracting partial conductivities, it is demonstrated that the main contribution to the conductivity is that of [C₄PYR]⁺ and [Tf₂N]^?. However, addition of Na⁺/Li⁺, although not significant on its own, produces a dramatic decrease in the partial conductivities of the RTIL ions. The origin of this indirect effect can be traced to the modification of the microscopic structure of the liquid as observed from the radial distribution functions, owing to the formation of [Na(Tf₂N)_n]^(n?1)? and [Li(Tf₂N)_n]^(n?1)? clusters at high concentrations. This formation hinders the motion of the large ions, hence reducing the total conductivity. We demonstrate that this clustering effect is common to both Li and Na, showing that both ions behave in a similar manner at a microscopic level in spite of their distinct ionic radii. This is an interesting finding for extending Li‐ion and Li‐air technologies to their potentially cheaper Na‐based counterparts.     

A Detailed Study of the (Electro)chemical Behavior of Bis(trifluoromethanesulfonyl)imide Based Ionic Liquids at Different Purification Steps

A systematic investigation of the major impurities content as well as of their effect on the electrochemical behavior of synthesized N‐butyl‐N‐methylpyrrolidinium (Py_1.4), N‐(2‐methoxyethyl)‐N‐methylpyrrolidinium (Py_1.102) and 1‐butyl‐3‐methylimidazolium (bmim) bis(trifluoromethanesulfonyl)imide has been carried out and the efficacy of an optimized multistep purification protocol for obtaining ILs suitable for electrochemical applications has been verified.     

A Rhodium Nanoparticle–Lewis Acidic Ionic Liquid Catalyst for the Chemoselective Reduction of Heteroarenes

We describe a catalytic system composed of rhodium nanoparticles immobilized in a Lewis acidic ionic liquid. The combined system catalyzes the hydrogenation of quinolines, pyridines, benzofurans, and furan to access the corresponding heterocycles, important molecules present in fine chemicals, agrochemicals, and pharmaceuticals. The catalyst is highly selective, acting only on the heteroaromatic ring, and not interfering with other reducible functional groups.     

Au(111)/咪唑基离子液体界面结构研究：阳离子侧链长度的影响

本文结合电化学方法与原子力显微镜力曲线技术,研究了两种烷基侧链长度不同的离子液体BMITFSA和OMITFSA在Au(111)电极表面附近的层状结构的数目和耐受力对电位的依赖性,探究了烷基侧链长度变化对界面层状结构的影响. 研究表明,不同烷基侧链长度的离子液体体系力-电位曲线形状基本相似. 在零电荷电位（the potential of zero charge,PZC）附近时,力值最小,因为此时电极表面荷电量较小,层状结构不稳定;电位偏离PZC的过程中,第一层层状结构力值呈现先增大后减小的趋势. 受到烷基侧链所处的不同位置影响,在PZC电位以负,短侧链离子液体的层状结构稳定性较好,而PZC电位以正,长侧链离子液体的稳定性较好.     

When Like Charged Ions Attract in Ionic Liquids: Controlling the Formation of Cationic Clusters by the Interaction Strength of the Counterions

The properties of ionic liquids are described by a subtle balance between Coulomb interaction, hydrogen bonding, and dispersion forces. We show that lowering the attractive Coulomb interaction by choosing weakly coordinating anions leads to the formation of cationic clusters. These clusters of like‐charged ions are stabilized by cooperative hydrogen bonding and controlled by the interaction potential of the anion. IR and NMR spectroscopy combined with computational methods are used to detect and characterize these unusual, counter‐intuitively formed clusters. They can be only observed for weakly coordinating anions. When cationic clusters are formed, cyclic tetramers are particularly stable. Therein, cooperative hydrogen‐bond attraction can compete with like‐charge repulsion. We present a simple but effective spectroscopic scale for the possibility of like‐charge attraction in ionic liquids, based on IR and NMR signatures.     

Cross-Linked Ionic Liquid Polymer for the Effective Removal of Ionic Dyes from Aqueous Systems: Investigation of Kinetics and Adsorption Isotherms

In the current study, we have synthesized an imidazolium based cross-linked polymer, namely, 1-vinyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide (poly[veim][Tf₂N]-TRIM) using trimethylolpropane trimethacrylate as cross linker, and demonstrated its efficiency for the removal of two extensively used ionic dyes—methylene blue and orange-II—from aqueous systems. The detailed characterization of the synthesized poly[veim][Tf₂N]-TRIM was performed with the help of ¹H NMR, TGA, FT-IR and FE-SEM analysis. The concentration of dyes in aqueous samples before and after the adsorption process was measured using an UV-vis spectrophotometer. The process parameters were optimised, and highest adsorption was obtained at a solution pH of 7.0, adsorbent dosage of 0.75 g/L, contact time of 7 h and dye concentrations of 100 mg/L and 5.0 mg/L for methylene blue and orange-II, respectively. The adsorption kinetics for orange-II and methylene blue were well described by pseudo-first-order and pseudo–second-order models, respectively. Meanwhile, the process of adsorption was best depicted by Langmuir isotherms for both the dyes. The highest monolayer adsorption capacities for methylene blue and orange-II were found to be 1212 mg/g and 126 mg/g, respectively. Overall, the synthesized cross-linked poly[veim][Tf₂N]-TRIM effectively removed the selected ionic dyes from aqueous samples and provided >90% of adsorption efficiency after four cycles of adsorption. A possible adsorption mechanism between the synthesised polymeric adsorbent and proposed dyes is presented. It is further suggested that the proposed ionic liquid polymer adsorbent could effectively remove other ionic dyes and pollutants from contaminated aqueous systems.