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ABSTRACT: The proof-of-principle for the separation of metals by solvent extraction using two mutually immiscible ionic liquids is given. Cobalt was extracted from the ionic liquid 1-ethyl-3-methylimidazolium chloride to the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate. A distribution ratio of 44 was obtained. Cobalt could be selectively separated from nickel, with a separation factor of 207. The extraction mechanism was elucidated using UV-VIS absorption measurements. The mutual solubility between the two ionic liquids was determined by (1)H NMR. Processing steps such as washing, stripping and regeneration of the ionic liquid phases are discussed.
Physical Chemistry Chemical Physics 05/2013; · 3.57 Impact Factor
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ABSTRACT: Uranium(VI) oxide has been dissolved in three different ionic liquids functionalized with a carboxyl group: betainium bis[(trifluoromethyl)sulfonyl]imide, 1-(carboxymethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and N-(carboxymethyl)-N-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide. The dissolution process results in the formation of uranyl complexes with zwitterionic carboxylate ligands and bis[(trifluoromethyl)sulfonyl]imide (bistriflimide) counterions. An X-ray diffraction study on single crystals of the uranyl complexes revealed that the crystal structure strongly depends on the cationic core appended to the carboxylate groups. The betainium ionic liquid gives a dimeric uranyl complex, the imidazolium ionic liquid a monomeric complex, and the pyrrolidinium ionic liquid a one-dimensional polymeric uranyl complex. Extended X-ray absorption fine structure measurements have been performed on the betainium uranyl complex. The absorption and luminescence spectra of the uranyl betainium complex have been studied in the solid state and dissolved in water, in acetonitrile, and in the ionic liquid betainium bistriflimide. The carboxylate groups remain coordinated to uranyl in acetonitrile and in betainium bistriflimide but not in water.
Inorganic Chemistry 02/2010; 49(7):3351-60. · 4.60 Impact Factor
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Peter Nockemann,
Michael Pellens,
Kristof Van Hecke,
Luc Van Meervelt,
Johan Wouters, Ben Thijs,
Evert Vanecht,
Tatjana N Parac-Vogt,
Hasan Mehdi,
Stijn Schaltin,
Jan Fransaer,
Stefan Zahn,
Barbara Kirchner,
Koen Binnemans
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ABSTRACT: A series of nitrile-functionalized ionic liquids were found to exhibit temperature-dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C(1)C(1CN)Pyr)(2)(Tf(2)N)(4)] and [Co(C(1)C(2CN)Pyr)(6)][Tf(2)N](8), which were isolated from ionic-liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt-containing ionic liquids.
Chemistry 12/2009; 16(6):1849-58. · 5.93 Impact Factor
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Peter Nockemann,
Koen Binnemans, Ben Thijs,
Tatjana N Parac-Vogt,
Klaus Merz,
Anja-Verena Mudring,
Preethy Chirukandath Menon,
Ravindran Nair Rajesh,
George Cordoyiannis,
Jan Thoen,
Jan Leys,
Christ Glorieux
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ABSTRACT: The ionic liquid (2-hydroxyethylammonium)trimethylammonium) bis(trifluoromethylsulfonyl)imide (choline bistriflimide) was obtained as a supercooled liquid at room temperature (melting point=30 degrees C). Crystals of choline bistriflimide suitable for structure determination were grown from the melt in situ on the X-ray diffractometer. The choline cation adopts a folded conformation, whereas the bistriflimide anion exhibits a transoid conformation. The choline cation and the bistriflimide anion are held together by hydrogen bonds between the hydroxyl proton and a sulfonyl oxygen atom. This hydrogen bonding is of importance for the temperature-dependent solubility properties of the ionic liquid. Choline bistriflimide is not miscible with water at room temperature, but forms one phase with water at temperatures above 72 degrees C (equals upper critical solution temperature). 1H NMR studies show that the hydrogen bonds between the choline cation and the bistriflimide anion are substantially weakened above this temperature. The thermophysical properties of water-choline bistriflimide binary mixtures were furthermore studied by a photopyroelectric technique and by adiabatic scanning calorimetry (ASC). By photothermal analysis, besides highly accurate values for the thermal conductivity and effusivity of choline bistriflimide at 30 degrees C, the detailed temperature dependence of both the thermal conductivity and effusivity of the upper and lower part of a critical water-choline bistriflimide mixture in the neighborhood of the mixing-demixing phase transition could be determined with high resolution and accuracy. Together with high resolution ASC data for the heat capacity, experimental values were obtained for the critical exponents alpha and beta, and for the critical amplitude ratio G+/G-. These three values were found to be consistent with theoretical expectations for a three dimensional Ising-type of critical behavior of binary liquid mixtures.
The Journal of Physical Chemistry B 02/2009; 113(5):1429-37. · 3.70 Impact Factor
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Peter Nockemann, Ben Thijs,
Kyra Lunstroot,
Tatjana N Parac-Vogt,
Christiane Görller-Walrand,
Koen Binnemans,
Kristof Van Hecke,
Luc Van Meervelt,
Sergey Nikitenko,
John Daniels,
Christoph Hennig,
Rik Van Deun
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ABSTRACT: The dissolution process of metal complexes in ionic liquids was investigated by a multiple-technique approach to reveal the solvate species of the metal in solution. The task-specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf(2)N]) is able to dissolve stoichiometric amounts of the oxides of the rare-earth elements. The crystal structures of the compounds [Eu(2)(bet)(8)(H(2)O)(4)][Tf(2)N](6), [Eu(2)(bet)(8)(H(2)O)(2)][Tf(2)N](6) x 2 H(2)O, and [Y(2)(bet)(6)(H(2)O)(4)][Tf(2)N](6) were found to consist of dimers. These rare-earth complexes are well soluble in the ionic liquids [Hbet][Tf(2)N] and [C(4)mim][Tf(2)N] (C(4)mim = 1-butyl-3-methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, (1)H, (13)C, and (89)Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X-ray absorption fine structure) and HEXS (high-energy X-ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry.
Chemistry 02/2009; 15(6):1449-61. · 5.93 Impact Factor
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ABSTRACT: The palladium-catalyzed hydrogenolysis of aromatic ketones to alkylbenzenes was studied in mixtures of ionic liquids to explore the promotional effect of these reaction media. Choline-based ionic liquids displayed complete miscibility with the aromatic ketone substrate at reaction temperature and a clear phase separation of the derived alkylbenzene product at room temperature. Selected ionic liquids were then assessed as reaction media in the hydrogenolysis of aromatic ketones over palladium catalysts. A binary mixture of choline and betainium bis(trifluoromethylsulfonyl)imide ionic liquids resulted in the highest conversion and selectivity values in the hydrogenolysis of acetophenone. At the end of the reaction, the immiscible alkylbenzene separates from the ionic liquid mixture and the pure product phase can be isolated by simple decantation. After optimization of the reaction conditions, high yields (>90 %) of alkylbenzene were obtained in all cases. The catalyst and the ionic liquid could be used at least three times without any loss of activity or selectivity.
ChemSusChem 12/2008; 1(12):997-1005. · 6.83 Impact Factor
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Peter Nockemann, Ben Thijs,
Tatjana N Parac-Vogt,
Kristof Van Hecke,
Luc Van Meervelt,
Bernard Tinant,
Ingo Hartenbach,
Thomas Schleid,
Vu Thi Ngan,
Minh Tho Nguyen,
Koen Binnemans
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ABSTRACT: Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by (1)H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined.
Inorganic Chemistry 11/2008; 47(21):9987-99. · 4.60 Impact Factor
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ABSTRACT: The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393 K on the basis of dielectric measurements in the frequency range from 1 to 10(7) Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion.
The Journal of Chemical Physics 03/2008; 128(6):064509. · 3.33 Impact Factor
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ABSTRACT: The crystal structure of the title compound, (C(6)H(11)N(2))(3)[EuBr(6)], consists of 1-ethyl-3-methyl-imidazolium cations and centrosymmetric octa-hedral hexa-bromido-europate anions. The [EuBr(6)](3-) anions are located at the corners and face-centres of the monoclinic unit cell. Characteristic hydrogen-bonding inter-actions can be observed between the bromide anions and the acidic H atoms of the imidazolium cations.
Acta Crystallographica Section E Structure Reports Online 01/2008; 64(Pt 7):m945. · 0.35 Impact Factor
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ABSTRACT: Choline saccharinate and choline acesulfamate are two examples of hydrophilic ionic liquids, which can be prepared from easily available starting materials (choline chloride and a non-nutritive sweetener). The (eco)toxicity of these ionic liquids in aqueous solution is very low in comparison to other types of ionic liquids. A general method for the synthesis and purification of hydrophilic ionic liquids is presented. The method consists of a silver-free metathesis reaction, followed by purification of the ionic liquid by ion-exchange chromatography. The crystal structures show a marked difference in hydrogen bonding between the two ionic liquids, although the saccharinate and the acesulfamate anions show structural similarities. The optimized structures, the energetics, and the charge distribution of cation-anion pairs in the ionic liquids were studied by density functional theory (DFT) and second-order (Møller-Plesset) perturbation theory calculations. The occupation of the non-Lewis orbitals was considered to obtain a qualitative picture of the Lewis structures. The calculated interaction energies and the dipole moments for the ion pairs in the gas phase were discussed.
The Journal of Physical Chemistry B 06/2007; 111(19):5254-63. · 3.70 Impact Factor
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ABSTRACT: Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.
The Journal of Physical Chemistry B 11/2006; 110(42):20978-92. · 3.70 Impact Factor
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ABSTRACT: The first examples of ionic liquids with rare-earth-containing anions are presented. These ionic liquids based on rare-earth thiocyanate complexes are liquid at room temperature, despite the multivalent character of the anionic building blocks.
Journal of the American Chemical Society 11/2006; 128(42):13658-9. · 9.91 Impact Factor
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ABSTRACT: Silver salts of the higher straight-chain alkanoic acids (silver soaps) and especially silver(I) behenate and silver(I) stearate are being used as the silver source in thermographic and photothermographic materials. The silver(I) alkanoates exhibit a complicated thermal behavior, and different phase transitions can be detected between the solid, crystalline state and the onset point of thermal decomposition. The phase transitions are due to a gradual breakdown of the layerlike structure of these compounds, and some of the phases are viscous mesophases. The silver alkanoates of the homologous series between silver propionate (C 3 H 5 O 2 Ag) and silver tetracosanoate (C 24 H 47 O 2 Ag) have been prepared, as well as silver hexacosanoate (C 26 H 51 O 2 Ag) and silver octacosanoate (C 28 H 55 O 2 Ag). The light stability of the compounds increases with increasing chain length. The room-temperature X-ray diffractograms indicate that the silver alkanoates consist of a bilayer structure. The thermal properties of these silver-containing metallomesogens were investigated by high-temperature X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The number and the nature of the phase transitions depends on the alkyl chain length. The thermal decomposition of the silver alkanoates with long alkyl chains proceeds in a liquid-crystalline state (mesophase), and leads to the formation of silver. The thermal behavior of silver behenate is discussed in detail.
03/2004;
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ABSTRACT: The palladium-catalyzed hydrogenolysis of aromatic ketones to alkylbenzenes was studied in mixtures of ionic liquids to explore the promotional effect of these innovative reaction media. First, the miscibility of a wide range of ionic liquids with aromatic ketones and ...
