离子液体的合成

离子液体作为一类新型的环境友好的。绿色溶剂”,具有很多独特的性质,在很多领域有着诱人的应用前景。本文主要介绍了以N,N’-二烷基咪唑阳离子,N-烷基吡啶阳离子与含氟阴离子,氯酸铝阴离子等形成的室温离子液体的合成方法。     

Crown ether bridged homo- and heterodinuclear copper(II) and nickel(II) cyclidene complexes: Interaction with anions

Homodinuclear (3CuCu, 3NiNi) and heterdionuclear (3CuNi) cyclidene complexes linked by two 1,10-diaza-18-crown-6 ethers were synthesized and their properties characterized. For the 3CuCu in the negative potential range the mixed-valence state Cu^I-Cu^II was observed and the comproportionation constants were determined. The redox potentials of M^II/III showed a good correlation with DN of the solvent. In acetonitrile solution containing 0.1 mol dm⁻³ Bu₄NPF₆ reversible M^II/III redox processes were observed. However, in the presence of stronger ion pairing anions (e.g. BF₄⁻ and ClO₄⁻) the “potential inversion” occurred. Redox potentials of dinuclear complexes were compared with mononuclear cyclidene complexes. The influence of selected anions (Cl⁻ and NO₃⁻) on the redox process M^II/III was studied. The effect of Cl⁻ anion was different for 3CuCu and 3NiNi. In 3CuCu coordination of two chloride anions took place after oxidation of copper centers. In the 3NiNi complex two Cl⁻ anions were coordinated to one of the nickel(II) centers facilitating oxidation, at different potentials, of both nickel(II) cations. The behaviour of heteronuclear complex with Cl⁻ anions was similar to 3NiNi. All dinuclear complexes interacted with NO₃⁻ anions and the observed potential shifts were larger for nickel(II) than for copper(II) cations.     

Synthesis,Crystal Structure,Electrochemical and Catalytic Properties of Hybrid Polyoxomolybdate Clusters-Based Terbium Complex

The inorganic–organic compound based on polyoxomolybdate [Tb(C₂H₆SO)₈][PMo₁₂ O₄₀]·2C₂H₆SO·½H₂O (I) has been isolated and structurally characterized by single-crystal X-ray molecular structure, IR spectra, thermogravimetric analysis and cyclic voltammetry measurements. The catalytic activities of (I) were also tested. The title compound crystallizes in monoclinic crystal system with C2/c space group. In the crystal, the polyoxidometalate anions are arranged in chains parallel to the [010] direction. The complex cations are located between these layers and linked to the neighbouring anions via weak C–H?O hydrogen bonding interactions leading to the formation of three dimensional network structure. Their catalytic activity toward organic dye is quite sizeable since the target removal is about 68% in the presence of the system POM-Tb/H₂O₂ after 120 min.     

New Sulfide and Selenide Glasses: Preparation, Structure, and Properties

The properties of many sulfide and selenide glasses correspond closely to related oxide systems; this correspondence can be correlated with the ratios of the valences and of the radii of the anions and cations. The analogy of chalcogenides to oxides in phase separation behavior is striking. Systematic substitutions prove the validity of Zachariasen's rules for covalent materials. The glass-former cations which tend to polymerize during cooling have a coordination number of 3 or 4. The comparison has been extended to network modifiers among the sulfides and selenides.     

Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties (2Ni and 3Ni) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni^II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni^II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl⁻ anions to the coordinated Ni^II in 2Ni and 3Ni resulted in an appreciable shift of both Ni^II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu^II complexes.     

Kinetics of discharge of zinc at the dropping mercury electrode

The rate of the discharge reaction of zinc ions at the dropping mercury electrode is diminished if the concentration of the indifferent surface inactive electrolyte is increased, because of the decrease of the potential difference in the diffuse double layer. It diminishes also with increase of radius of the alkali-metal cations present in the electrolyte and with increase of charge of the cation of the electrolyte. A strong retarding effect is exhibited by tetraalkylammonium cations, which increases with the size of the alkyl group. The electrode reaction rate increases in presence of iodide anions, as manifested by formation of a new, more positive wave. In presence of iodide and tetraalkylammonium cations together the process is accelerated at more positive potentials and is retarded at more negative potentials.

All these phenomena are analogous to those observed with the hydrogen-evolution reaction at the mercury electrode, and are the opposite of those observed with anions of the persulphate type.

Abstract

La vitesse de décharge de Znl²⁺ sur électrode à mercure gouttante diminue quand s'accroît la concentration superficielle d'un électrolyte inactif, par suite de l'abaissement de la tension électrique dans la couche diffuse. Elle diminue aussi quand s'accroîssent le rayon on la charge des cations de l'électrolyte. Les cations tétraalkylammonium exercent un effet fortement retardateur, qui augmente avec l'encombrement du groupe alkyl. La vitesse s'élève par centre en présence d'anions I⁻. Si cet anion est accompagné d'un des cations précédents, le processus s'accélère aux tensions plus positives et se ralentit aux tensions plus négatives. Tons ces phénomènes, contrastant avec ceux manifestés avec les anions du type persulfate, sont comparables à ceux observés dans l'évolution d'hydrogène sur électrode de mercure.

Abstract

The influence shown by the composition of the electrode double layer on the electrode reaction rate of the zinc ion is quite similar to analogous effects observed with the hydrogen-evolution reaction at mercury electrodes. The decrease of the rate of the latter process with increase of the radius of alkali-metal cations, of the charge of the cation of the electrolyte and of the concentration of the electrolyte was described by Herasymenko and lendyk.²¹ The strong retardation of this process by quaternary cations and the acceleration by iodide was found by Yofa, Kabanov and co-workers.²² Tsa Chuan Sin and Yofa²³ observed the combined effect of iodide and tetraalkylammonium cations which at positive potentials accelerate the hydrogen evolution reaction slightly over the value in presence of iodide only, but retard it at more negative potentials.

From the similar features of both reactions it may be concluded that in spite of a different total reaction path, the rate-determining step is identical, i.e. the transfer of the charged particle from its hydration sheath to the electrode. It is expected that analogous phenomena will be observed with other cations which are not adsorbed too strongly at the electrode (cf. the influence of surface-active cations on the discharge of T1⁺ and Cd^{2+ 24,25}).

All the effects of the double-layer structure connected with the electrode reaction of the zinc ion are just the opposite of those observed with the reduction of anions of persulphate type.²⁰     

The uptake of copper from aqueous solution by immobilized fungal biomass

The removal of cupric ions from aqueous solution by a biosorption column in which the Rhizopus arrhizus fungal biomass was immobilized in reticulated foam biomass support particles was studied. Solution pH was found to be crucial to copper uptake, with the optimum range being 6·7–7·0. The removal efficiency was usually higher at low influent copper concentration and long residence time. The presence of other cations and anions inhibited copper uptake in the following order: for the cations, Mn²⁺ ? Zn²⁺ > Cd²⁺ > Mg²⁺ > Ca²⁺; for the anions, EDTA ? SO ? Cl^?. The biosorption process was fully reversible and regenerated columns showed undiminished performance.     

Separation of heterocyclic nitrogen compounds from coal tar fractions via ionic liquids: COSMO-SAC screening and experimental study

Ionic liquids (ILs) have been applied as a promising solvent for the separation of different kinds of compounds. But the enormous combination possibilities of the cations and anions make it a challenging task to screen an appropriate IL for a specific application. Thus, the method for screening IL candidates based on the COSMO-SAC model is presented and illustrated to extract heterocyclic nitrogen compounds, indole and carbazole, from coal tar fractions. Also, the σ-profile analysis is used to evaluate the effect of different types of cations and anions, and systematically confirmed the structure–activity relationships for the extraction process. Then, 22 cations and 19 anions are screened as the initial structures of the potential extractants from a σ-profile database (containing 39 cations and 29 anions). Along with the rigorous evaluation criterion proposed in this work, three IL extractants are adopted. Afterwards, the extractive ability of the candidates is experimentally investigated.     

Highly Efficient,Tripodal Ion-Pair Receptors for Switching Selectivity between Acetates and Sulfates Using Solid–Liquid and Liquid–Liquid Extractions

A tripodal, squaramide-based ion-pair receptor 1 was synthesized in a modular fashion, and ¹H NMR and UV-vis studies revealed its ability to interact more efficiently with anions with the assistance of cations. The reference tripodal anion receptor 2, lacking a crown ether unit, was found to lose the enhancement in anion binding induced by presence of cations. Besides the ability to bind anions in enhanced manner by the “single armed” ion-pair receptor 3, the lack of multiple and prearranged binding sites resulted in its much lower affinity towards anions than in the case of tripodal receptors. Unlike with receptors 2 or 3, the high affinity of 1 towards salts opens up the possibility of extracting extremely hydrophilic sulfate anions from aqueous to organic phase. The disparity in receptor 1 binding modes towards monovalent anions and divalent sulfates assures its selectivity towards sulfates over other lipophilic salts upon liquid–liquid extraction (LLE) and enables the Hofmeister bias to be overcome. By changing the extraction conditions from LLE to SLE (solid–liquid extraction), a switch of selectivity from sulfates to acetates was achieved. X-ray measurements support the ability of anion binding by cooperation of the arms of receptor 1 together with simultaneous binding of cations.     

Preparation of new layered double hydroxide,Zn-Mo LDH

Layered double hydroxide (LDH) is prepared conventionally with bivalent and trivalent cations. We recently reported that the preparation of Zn-Ti LDH consisting of bi and tetravalent cations is possible through the decomposition of urea. In this study, Zn-Mo LDH consisting of bi and hexavalent cations were prepared and reacted with organic monocarboxylic and dicarboxylic acids. Interlayer spacing of the prepared LDH (Zn-Mo-CO₃) contained carbonate anions between the layers was 0.72 nm. The spacing was small compared to usual LDH (Zn-Al-CO₃) of 0.76 nm in the case of carbonate anion as the guest. Also, TG analysis indicated that the electrostatic force between the Zn-Mo layers and carbonate anions was larger than those of Zn-Al LDH. Certainly, the carbonate anions in Zn-Mo LDH decomposed at 260°C while they in usual LDH decomposed at 230–240°C. ESCA showed that Mo⁵⁺ had changed to Mo⁶⁺ through the preparation procedure. These results showed the preparation of layered double hydroxides consisting of bivalent and hexavalent cations. By the intercalation of Zn-Mo LDH with suberic acid at 60°C, a sharp peak was observed at 1.06 nm and the peak of LDH itself (0.72 nm) disappeared. This result has suggested that the intercalation of organic acid into new LDH was performed completely.     

Ionic Liquid Confined in Nafion: Toward Molecular‐Level Understanding

In this article, multiscale simulation methods were used to study structural and transport properties of Nafion–ionic liquid composite membranes that are novel proton conducting materials for fuel cells. Coarse‐grained model for 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquid was first developed in the framework of BMW‐MARTINI force field. Coarse‐grained simulation results of bulk [bmim][BF₄] ionic liquid show good agreement with all‐atom simulation results and experimental data. Nafion–[bmim][BF₄] composite membranes were then simulated using all‐atom and coarse‐grained models. Ionic liquid cluster formation inside Nafion was revealed by coarse‐grained simulations. Diffusion coefficients of both [bmim]⁺ cations and anions are reduced by one to two orders of magnitude depending on their concentrations in Nafion membrane. [Bmim]⁺ cations have faster self‐diffusion coefficient than anions, while this phenomenon is more pronounced when ionic liquids are confined in Nafion. This work provides molecular basis for understanding Nafion–ionic liquid composite membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2630–2639, 2013     

Kinetic study of atom transfer radical polymerization of methyl methacrylate in ionic liquids

The kinetics of methyl methacrylate (MMA) homopolymerization performed by atom transfer radical polymerization (ATRP) is investigated in detail using ethyl‐2‐bromopropionate (EPN‐Br) as initiator, CuBr as catalyst, and pentamethyldiethylenetriamine (PMDETA) as ligand in ionic liquids (ILs) and acetonitrile. ILs in this research covered two different substitutional imidazolium cations and anions including halogen and halogen‐free ones. The typical cations include 1‐butyl‐3‐methylimidazolium, 1‐ethyl‐3‐methylimidazolium and the typical anions include bromide, tetrafluoroborate. The effects of solvents, temperature, and reaction ingredients ratios on the polymerization kinetics are all investigated in this article and the apparent energy of activation (ΔE) calculated for the ATRP of MMA in 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate is 6.95 KJ/mol. The number‐average molecular weights (M_n) increase linearly with conversion but are much higher than the theoretical values. It is probably due to the low concentration of deactivator at the early stage of polymerization and the lower bond energy of C‐Br in PMMA‐Br than that in EPN‐Br. Moreover, the catalyst is easily separated from the polymer and the regenerated catalyst is reused for more than three times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Combined analysis of self-diffusion, conductivity, and viscosity data on room temperature ionic liquids

The self-diffusion coefficient of anions and cations, the ionic conductivity and the viscosity of four room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI), 1-butylpyridinium tetrafluoroborate (BPBF₄), and 1-butylpyridinium bis(trifluoromethylsulfonyl)imide (BPTFSI) were analysed within a comprehensive ionic transport model. The experimental data, covering wide temperature ranges, were taken from the work of Noda et al. [J. Phys. Chem. B, 105, 2001]. To compare the dc conductivity with the self-diffusion coefficients, the former quantity was converted into a charge diffusivity D_σ using the Nernst-Einstein equation. In a similar way, we calculated a viscosity-related diffusivity D_η with the aid of the Stokes-Einstein equation. Taking three mobile species into account, i.e., single cations, single anions and neutral ion pairs, our model yields their individual diffusivities that obey a uniform Vogel-Tammann-Fulcher-like temperature dependence described by common values of the parameters B and T₀. Evaluating simultaneously all experimental data within this model yields the contribution of ion pairs to the self-diffusion coefficient of cations and anions separately. We further obtain the temperature-independent cation transference number and the effective hydrodynamic radius, which are important characteristics of charge and mass transport in these ionic liquids.     

CO oxidation over CuO catalysts prepared with different precipitants

CuO catalysts, prepared by the precipitation method using different precipitants such as ammonium hydroxide, sodium hydroxide, sodium carbonate and sodium hydrogen carbonate were applied to CO oxidation. Among the catalysts studied, CuO synthesized with sodium hydrogen carbonate showed the highest activity for CO oxidation. With the water vapor present in the feed gas, the catalytic activity decreased considerably due to reduction in the number of active sites by competitive adsorption between water vapor and CO. The H₂-TPR and CO-TPD results showed that existing Na⁺ cations and HCO ₃ ^? and CO_3/2? anions on the CuO surface could weaken the copper-oxygen bond strength and accelerate the mobility of oxygen on the surface or lattice. Finally, the morphology of the CuO crystals was dependent on the precipitants, and the introduction of Na⁺ cations and various anions resulted in the formation of smaller crystals.     

An experimental study of electroreduction of CO2 to HCOOH on SnO2/C in presence of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) and anions (HCO3-, Cl-, Br- and I-)

It is well-known that the electrolytes can influence the electrochemical reduction of carbon dioxide (ERCO₂) in aqueous media. In this work, we explore the effects of alkali metal cations and anions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, HCO₃^-, Cl^-, Br^-, I^-) on the current density and product selectivity for the ERCO₂ into formic acid (HCOOH) on the SnO₂/carbon paper (SnO₂/C) electrode. Results of the ERCO₂ experiments show that for the cations, the promotion effects on current density and faradaic efficiencies (FEs) are in the order of Li⁺ < Na⁺ < K⁺ < Cs⁺ < Rb⁺. For the anions, the current density values are in the order of NaHCO₃ < NaCl < NaBr < NaI and KHCO₃ < KCl ≈ KI < KBr, respectively, and that on the FEs for the formation of the HCOOH (FE_HCOOH) is HCO₃^- < Cl^- < Br^- < I^-. Based on this result, the effects of alkali metal cations and anions on ERCO₂ are discussed.     

Reverse osmosis separation of inorganic salts using polyvinylalcohol membranes

Permeabilities and fluxes of fifty-four mono-, divalent anions and cations of sodium and chloride salts have been tested under experimental conditions of 50 bar and room temperature through asymmetric polyvinylalcohol membranes crosslinked with formaldehyde. The following percent rejections among these salts are given: sodium salts of divalent anions (70–80%), chloride salts of divalent cations (30–40%), H₂ SO₄ (30%), sodium salts of monovalent monoatomic anions, chloride salts of monovalent cations (15– 30%) and HCl, HNO₃, NaOH, KOH (10–20%). Sodium salts of monovalent polyatomic anions gave higher rejections than those of monovalent monoatomic anions. Higher rejection of divalent anions than that of divalent cations of chloride salts suggests that the membrane surface is negatively charged.     

Zero-point potentials of metals in molten alkali halides and their binary mixtures

The zero-point potentials of liquid bismuth, lead, and indium in molten alkali halides and their binary mixtures were determined by electrocapillary-curve method, using the same led reference electrode. They are found to grow more electropositive as temperature and alkali cation radii increase and those of halide anions decrease. Such dependence is supposed to be caused by the changing of work function as a result of capturing the emitted electrons by alkali cations and of the existence of the potential jumps to which the dipoles induced by the cations on the halide anions give rise on the interface metal/salt melt. The zero-point potential of bismuth in the binary molten mixtures with common halide anions is shown to reach the values characteristic of the heavier components when their contents in the mixtures amount to about 40 mol% and to remain nearly constant by the further increase of their concentration.s But in the mixtures with common alkali cations the zero-point potential changes fairly monotonously by substituting one halide anion for another. The difference in behaviour of these two groups of the binary mixtures gives evidence that in the molten alkali halides and their mixtures most of the halides anions are bound by the cations in (auto)complexes or associates whereas most of the alkali cations remain relatively loose among them.     

Synthesis, characterization and photophysical properties of novel fluorene-based copolymer with pendent urea group: Fluorescent response for anions through H-bonding interaction

A novel fluorene-based copolymer P₁ with diphenyl urea as pendent group, as well as its analogous copolymer P₂ without urea group for comparison, were synthesized by Suzuki-coupling reaction, and characterized by ¹H NMR, EA, IR and GPC. The polymers were brightly blue emissive in THF, DMF, or DMSO solution. Anion titration experiments carried out in THF indicate that the polymer P₁ has good selectivity for fluoride ion, acetate ion, and dihydrogen phosphate ion, and the sensitivity and selectivity of P₁ toward these anions come from the strong hydrogen-bond interaction between the anions and the urea group of the copolymer. This new system utilizing the strong luminescence property of the polyfluorene as reporter and the hydrogen-bond-forming ability of urea group may act as novel effective anions receptor and chemosensor.     

Where is the Anion Extraction Going?

Reactive extraction processes represent efficient and smart technologies for separation and concentration of metal ions in solution, which are frequently used in industry. Despite the importance of anions in biology, medicine, environment and industry, practical examples of anion extraction are relatively limited compared to metal ion separation. Anion extraction processes are mainly based on the nonspecific ion pair formation with hydrophobic ammonium cations. In this case the phase transfer of anions is dominated by their lipophilicity. The reasons for this situation are closely connected with the specific features of anions in contrast to cations. Novel approaches for specific binding and selective transport of anionic components are based both on the better understanding of the biological role of anions and on the possibilities of supramolecular chemistry to create receptor architectures with complementary binding modes for anions. In the given review the authors discuss present research tendencies and application possibilities of new extractant types for separation and concentration of anionic species in solution.