Ben Thijs

KU Leuven, Leuven, VLG, Belgium

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Publications (28)88.81 Total impact

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    ABSTRACT: Metal oxides were found to dissolve in different imidazolium ionic liquids with a hydrogen atom in the C2 position of the imidazolium ring, but not if a methyl substituent was present in the C2 position. The crystal structure of the product that crystallised from an ionic liquid containing dissolved silver(i) oxide showed that this was a silver(i) carbene complex. The presence of carbenes in solution was proven by (13)C NMR spectroscopy and the reactions were also monitored by Raman spectroscopy. The dissolution of other metal oxides, namely copper(ii) oxide, zinc(ii) oxide and nickel(ii) oxide, was also studied in imidazolium ionic liquids and it was found that stable zinc(ii) carbenes were formed in solution, but these did not crystallise under the given experimental conditions. A crystalline nickel(ii) carbene complex could be obtained from a solution of nickel(ii) chloride dissolved in a mixture of 1-butyl-3-methylimidazolium and 1-ethyl-3-methylimidazolium acetate.
    Dalton Transactions 01/2014; · 3.81 Impact Factor
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    ABSTRACT: The dissolution of metal oxides in an acid-saturated ionic liquid, followed by selective stripping of the dissolved metal ions to an aqueous phase is proposed as a new ionometallurgical approach for the processing of metals in ionic liquids. The hydrophobic ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) saturated with a concentrated aqueous hydrochloric acid solution was used to dissolve CaO, NiO, MnO, CoO, CuO, ZnO and Fe2O3. It was found that nickel(II) and calcium(II) could be separated from all other transition metals present in the ionic liquid phase by stripping at high chloride concentrations. By scrubbing the ionic liquid solutions phase with water, manganese(II) and cobalt(II) could be stripped together with a fraction of iron(III) and copper(II), leaving zinc(II) and the remainder of copper(II) and iron(III) in the ionic liquid phase. These metal ions could be removed from the ionic liquid using ammonia. Copper(II) and zinc(II) formed ammine complexes and were back-extracted, while iron(III) precipitated as iron(III) hydroxide. After removal of all the metals present in the ionic liquid phase, the ionic liquid was prepared for reuse. Unfortunately, the mutual separations nickel–calcium, cobalt–manganese, or zinc–copper could not be achieved. This system would be useful when nickel is the metal of interest, since separation of nickel from all other transition metals present in the solution is achieved by one stripping step.
    Hydrometallurgy 01/2014; · 2.17 Impact Factor
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    ABSTRACT: A batch of the protic ionic liquid pyrrolidinium nitrate exploded while drying it under reduced pressure at 110 °C, using a rotary evaporator with an oil bath.
    Green Chemistry 11/2013; 15(12). · 6.83 Impact Factor
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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; · 3.83 Impact Factor
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    ABSTRACT: A continuous ionic liquid extraction process using the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos® IL 101) has been developed for the selective extraction of cobalt from nickel. The performance of this continuous extraction process is competitive with that of currently applied industrial processes. Moreover, the elimination of volatile odorous compounds from the extraction phase leads to environmentally friendlier and healthier working conditions.
    Green Chemistry 01/2013; 15(11):3160. · 6.83 Impact Factor
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    ABSTRACT: A green solvent extraction process for the separation of cobalt from nickel, magnesium and calcium in chloride medium was developed, using undiluted phosphonium-based ionic liquids as extractants. Cobalt was extracted to the ionic liquid phase as the tetrachlorocobaltate(II) complex, leaving behind nickel, magnesium and calcium in the aqueous phase. Manganese is interfering in the separation process. The main advantage of this ionic liquid extraction process is that no organic diluents have to be added to the organic phase, so that the use of volatile organic compounds can be avoided. Separation factors higher than 50000 were observed for the cobalt/nickel separation from 8 M HCl solution. After extraction, cobalt can easily be stripped using water and the ionic liquid can be reused as extractant, so that a continuous extraction process is possible. Up to 35 g L−1 of cobalt can be extracted to the ionic liquid phase, while still having a distribution coefficient higher than 100. Instead of hydrochloric acid, sodium chloride can be used as a chloride source. The extraction process has been upscaled to batch processes using 250 mL of ionic liquid. Tri(hexyl)tetradecylphosphonium chloride, tri(butyl)tetradecylphosphonium chloride, tetra(octyl)phosphonium bromide, tri(hexyl)tetradecylphosphonium bromide and Aliquat 336 have been tested for their performance to extract cobalt from an aqueous chloride phase to an ionic liquid phase. Tri(hexyl)tetradecylphosphonium chloride (Cyphos IL 101) turned out to be the best option as the ionic liquid phase, compromising between commercial availability, separation characteristics and easiness to handle the ionic liquid.
    Green Chemistry 06/2012; 14(6):1657-1665. · 6.83 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. · 4.59 Impact Factor
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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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    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 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. · 3.61 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. · 7.48 Impact Factor
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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. · 4.59 Impact Factor
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    ABSTRACT: The structure of one tautomer (amine form) of cyano-carbamimidic acid ethyl ester or (amino-ethoxy-methylidene)aminoformonitrile (CAS: 13947-84-7) was determined by single crystal X-ray diffraction. Ab initio quantum chemical calculations at the B3LYP, MP2 and G3 levels were performed to investigate the stability and the formation of the different tautomers and conformers. The calculations indicate that the amine form is the more stable tautomer, showing a high degree of electron conjugation. The most stable amine conformer located by the calculations corresponds to the crystallized structure. On the contrary, in the less stable imine form, the conjugation is separated by a N2–C2 single bond.
    Journal of Molecular Structure THEOCHEM 08/2008; 885(s 1–3):97–103. · 1.37 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. · 3.12 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. · 3.61 Impact Factor
  • Ben Thijs
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    ABSTRACT: De doelstelling van dit doctoraatsproefschrift was het ontwerpen van gefunctionaliseerde ionische vloeistoffen, zodat deze systemen metaalverbindingen kunnen oplossen. Ondanks het grote aantal beschikbare publicaties over ionische vloeistoffen, zijn er nog maar weinig ionische vloeistoffen gekend die in staat zijn om metaalverbindingen in hoge concentraties op te lossen. Voor een heel aantal toepassingen waaronder elektrodepositie en katalyse, is dit een groot nadeel. Bij de keuze van de precursoren werd rekening gehouden met de beschikbaarheid, de prijs en de toxiciteit van het kation. Om een nuttige ionische vloeistof te synthetiseren is het belangrijk dat dit op een eenvoudige en goedkope manier kan gebeuren. Ook het aantal synthese stappen om de ionische vloeistoffen te functionaliseren werd beperkt. Om metalen te kunnen oplossen, moet de ionische vloeistof de mogelijkheid bezitten het metaal te coördineren. Aan deze vereiste kan worden voldaan door functionele groepen te incorporeren. In dit werk werd gekozen voor carboxylaatgroepen. Als eerste werd het betaïne kation geselecteerd als mogelijke bouwsteen voor een gefunctionaliseerde ionische vloeistof. Dit kation is gemakkelijk beschikbaar (als betaïne hydrochloride zout), relatief goedkoop en als voedingsbestanddeel weinig toxisch. Om een hydrofobe ionische vloeistof te bekomen werd het oorspronkelijke chloride anion uitgewisseld voor een bistriflimide anion, wat het ‘referentie’ anion is geworden voor hydrofobe ionische vloeistoffen. Het hydrofobe karakter van deze verbinding is alleen geldig bij relatief lage temperaturen. Opwarming van een twee-fase systeem, water-ionische vloeistof leidt tot een homogene fase. Terug afkoelen resulteert opnieuw tot een fasescheiding. Door de aanwezigheid van de carboxylaatgroep, konden metaaloxiden in deze ionische vloeistoffen in hoge concentraties worden opgelost. Een hele diverse reeks van metaaloxiden werd opgelost en de metaalcomplexen werden gekarakteriseerd. Uit deze studie bleek dat het oplossend vermogen selectief was: niet elk metaaloxide kon opgelost worden. Voor toepassingen is het belangrijk dat de metalen en de ionische vloeistoffen, nadat ze hun taak hebben uitgevoerd, kunnen worden gerecupereerd. Nadat metaaloxiden in de betaïne ionische vloeistoffen zijn opgelost, kan door aanzuren met een waterige oplossing zowel het metaal als de ionische vloeistof gerecycleerd worden. De kristalstructuur van de ionische vloeistof gaf informatie over de positie van de ionen in de vaste toestand. Er werden twee structurele varianten van de betaïne ionische vloeistof gevonden, afhankelijk van de kristallisatie-methode. Om de interacties tussen de ionen van de ionische vloeistof te doorgronden werden DFT-berekeningen ( DFT = density functional theory ) uitgevoerd. Hieruit werd informatie gehaald over de waterstofbrug en de elektronenverdelingen van de ionen. Uit de structuurstudie van de metaalcomplexen, die onstaan door het oplossen van metaaloxiden of metaalhydroxiden, bleek afhankelijk van het metaal een heel gamma aan structuren te worden gevormd. Er werden dimeer structuren gevonden voor zowel een koper(II), een dysprosium(III) en een europium(III) complex, trimeren voor een kobalt(II)complex, tetrameren voor een mangaan(II)complex, pentameren voor een nikkel(II)complex, polymeren voor een cadmium(II) en zilver(I)complex, en cluster vorming voor een lood(II) verbinding . Structurele variaties in het betaïne kation werden aangebracht om de eigenschappen van de ionische vloeistoffen te varieren. Zo kan de ‘phase switching’ temperatuur, het smeltpunt en het oplosbaarheidsgedrag worden gevarieerd. Toch blijft de invloed van deze veranderingen beperkt en worden de eigenschappen vooral door de carboxylaatgroep bepaald. Van N-carboxymethylpyridinium bistriflimide, van P-carboxymethyl-P-tributylfosfonium bistriflimide en van N-carboxymethyl-N-methylmorfolinium ethyl ester werd de structuur bepaald. Enkele metaalcomplexen van deze betaïne analogen werden structureel gekarakteriseerd. Om aan te tonen dat de carboxylaat functionele groep belangrijk is voor het oplossend vermogen van metaaloxiden of metaalzouten, werd het choline kation gebruikt als bouwsteen van een ionische vloeistof. Ook dit kation is evenals betaïne een voedingsbestanddeel dat o.a. in kippenvoer gebruikt wordt. Door het ontbreken van een coördinerende groep, is de oplosbaarheid van metaalzouten in deze ionische vloeistof laag. Deze ionische vloeistof (choline bistriflimide) vertoonde ook een ‘phase switching’-gedrag en had een hoge UV-transparantie. Deze laatste eigenschap kan interessant zijn voor fotochemische reacties of spectroscopische toepassingen. Om de toxiciteit te verlagen en de biodegradeerbaarheid van de choline ionische vloeistof te verhogen, werden laag toxische anionen als bouwstenen gekozen. Zo werd gekozen voor saccharinaat en acesulfamaat als anionen. De toxiciteitstudie van deze ionische vloeistoffen bevestigde hun ‘groen’ karakter. Om metalen in ionische vloeistoffen te brengen kunnen zoals hierboven besproken, coördineerde groepen worden bevestigd aan de ionen of de metaalionen kunnen worden ingebouwd als onderdeel van de ionische vloeistof. Dit werd verwezenlijkt door lanthanide hexa-, hepta- en octathiocyanaten als anionen te gebruiken. Als kation werd gekozen voor de gekende 1-butyl-methylimidazolium. Door de stoichiometrie van de componenten tijdens de synthese aan te passen werden hexa-, hepta- en octathiocyanaat anionen verkregen. Op deze manier werden lanthanide-houdende ionische vloeistoffen gesynthetiseerd van de lanthanidereeks, die vloeibaar waren op of rond kamertemperatuur. Van de heptathiocyanaat lanthanide ionische vloeistoffen konden kristalstructuren worden bepaald. Om aan te tonen dat ook in de vloeistoffase de thiocyanaat liganden gecoördineerd bleven aan de lanthanide ionen, werden EXAFS (extended X-ray absorption fine structure) metingen uitgevoerd. Met dit werk hebben we aangetoond dat het onderzoeksgebied van ionische vloeistoffen en hun toepassingen kan uitgebreid worden door het incorporeren van functionele groepen. Structureel onderzoek en DFT berekeningen helpen daarbij om meer inzicht te krijgen in de chemie van deze gefunctionaliseerde ionische vloeistoffen. Metaalhoudende ionische vloeistoffen zijn materialen met interessante eigenschappen die nieuwe syntheseroutes mogelijk maken, bv. voor een vaste-stof chemie op lage temperatuur of voor kristallisatie (‘crystal engineering’) vanuit ionische vloeistoffen. Door het gebruik van laag-toxische ionen is het mogelijk om biocompatibele ionische vloeistoffen te ontwikkelen. Deze resultaten tonen aan dat de taakspecifieke ionische vloeistoffen veelbelovende materialen kunnen zijn – ook voor de anorganische chemie. The main goal of this PhD thesis was to design new task-specific ionic liquids with the ability to dissolve metal compounds. Despite the large quantity of papers published on ionic liquids, not much is known about the mechanisms of dissolving metals in ionic liquids or about metal-containing ionic liquids. Additionally, many of the commercially available ionic liquids exhibit a very limited solubilizing power for metal compounds, although this is for many applications like electrodeposition and catalysis one of the essential features. To enhance the ability of ionic liquids to incorporate metals in ionic liquids, functional groups that are able to coordinate to the metal ions are required. Task-specific ionic liquids combine, in the best case, a solubilizing power that is comparable with organic solvents with the “green” character of ionic liquids, which makes them environmental friendly solvents. Before these compounds will be applicable on larger scale, these functionalized ionic liquids have to be cheap and easily accessible. Firstly, a protonated betaine bistriflimide, [Hbet][Tf2N], was introduced. This is a cheap and easily accessible functionalized ionic liquid with the ability to dissolve large quantities of metal oxides and metal hydroxides. The metal solubilizing power of this compound 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 and silver(I) oxide. Insoluble or very poorly soluble are iron(III) and manganese(II) oxides, cobalt(II) oxides, as well as aluminium oxide. 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 into the aqueous phase, the ionic liquid can be separated and recycled. Betainium bistriflimide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 °C (“phase switching” behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase switching 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 betainium cation, the bistriflimide anion, as well as of the cation-anion pairs were studied by density functional theory calculations (DFT). Additionally, the crystal structures of two modifications of this ionic liquid were determined. A range of crystal structures of the metal complexes obtained from the above mentioned functionalized ionic liquid were examined. This study revealed a rich structural variety especially of oligonuclear complexes, whereas in the literature mainly monomeric or polymeric complexes with this type of ligands are known. Dimeric betaine bistriflimide structures were found for the dysprosium(III) compound; the europium(III) compound and for the copper(II) compound; a trimeric betaine bistriflimide structure for the cobalt(II) compound; a tetrameric betaine bistriflimide structure for the manganese(II) compound; a pentameric betaine bistriflimide structure for the nickel(II) compound; , a cluster formation for the lead(II) compound; and polymeric structures for the cadmium(II) compound; and the silver(I) compound. In the crystal structure of cobalt(II) betaine bistriflimide, pure ionic liquid [Hbet][Tf2N] co-crystallized. The cation-anion interaction found in the crystal structure of the pure ionic liquid remained in the metal complex. No hydrogen bonding between the ionic liquid and the metal complex could be observed. It was demonstrated that ionic liquids might be good media for crystal engineering. In order to modify the physical properties of the betainium ionic liquid, structural modifications have been introduced. Different kinds of cations, all bearing a carboxylic functional group, were applied. Six cations with a positively charged nitrogen ion – l-carnitine, pyrrolidinium, morpholinium, pyridinium, piperidinium, imidazolium and one with a positively charged phosphonium ion - tributylphosphonium, were studied. Despite the rich structural variation, surprisingly small differences in physical properties of these ionic liquids were observed. This can be explained by the strong and dominating influence of the carboxylic group on the physical properties. To study the influence of the carboxylic group, an ionic liquid with a hydroxyl group instead of the carboxylic group, choline bistriflimide, was introduced. Due to this hydroxyl group, the ionic liquid showed only a limited solubility towards metal compounds. This hydrophobic ionic liquid also shows a “phase switching” behavior; this occurred at higher temperatures than in the case of the betainium bistriflimide ionic liquid. Due to the absence of a conjugated system, this ionic liquid possesses a high UV-transparency. This can be an interesting property for the application of this choline bistriflimide ionic liquid as medium for photophysical reactions or as a solvent for spectroscopy. 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 with other types of ionic liquids. A general method for the synthesis and purification of hydrophilic ionic liquids has been demonstrated. The method implies a silver-free metathesis reaction, followed by the purification of the ionic liquids by ion-exchange chromatography. The crystal structures show a marked difference in hydrogen bonding between the two ionic liquids [Chol][Sac] and [Chol][Ace], 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). For a qualitative picture of the Lewis structure the occupation of the non-Lewis orbitals was considered. The calculated interaction energies and the dipole moments for the ion-pairs in the gas phase have been discussed. In the last chapter, a different strategy to incorporate metals into ionic liquids was introduced. A lanthanide thiocyanate anion was synthesized and used as component for an ionic liquid. By using this anion in combination with a 1-butyl-3-methylimidazolium (C4mim) cation the first lanthanide-containing ionic liquids were obtained. These compounds have melting points ranging from 28 °C (Nd) to 39 °C (Y). The general formula for these compounds is [C4mim] x -3[Ln(NCS) x (H2O) y ] ( x = 6-8; y = 1-2). Depending on the stochiometric amounts of [C4mim][SCN] used during the metathesis reaction, different lanthanide-containing ionic liquids could be obtained. The crystal structure of the ionic liquids with seven thiocyanates ([C4mim]4[La(NCS)7(H2O)], [C4mim]4[Pr(NCS)7(H2O)]) and six thiocyanates ([C4mim]3[Y(NCS)6(H2O)]) coordinated to the lanthanide ion could be determined. Crystallization of these compounds is favored because of the water molecule which completes the coordination sphere of the lanthanide ion and promotes an ordering of the complexes by hydrogen bonding. In order to get information about the structure of these lanthanide-containing ionic liquids also in the liquid state, EXAFS measurements were performed. For this study, the europium(III) ion was used. Europium(III) ionic liquids with three different compositions (6, 7 and 8 thiocyanates) were examined. A coordination of the nitrogen atoms of the thiocyanates to the lanthanide ions could be approved for all three compounds in the liquid state. In future work, further modifications of the chemical and physical properties of the betainium type ionic liquids should be applied to broaden the field of potential applications of these task-specific ionic liquids. For example, other N-alkylcarboxylic group functionalized cations with longer alkyl chains replacing the methyl group are conceivable and might change the solubility in more apolar solvents. The application of different functional groups like nitrile of thiol groups might change the complexing ability. A further extension towards new functionalities could be the attachment of mesogenic groups to the nitrogen atom, so that ionic liquid crystals might be obtained. The functionalized ionic liquid crystals might then be used to obtain metallomesogenes which combine the properties of ionic liquids with the intrinsic properties of the metal ions incorporated. Preliminary experiments have shown that combining two metal oxides dissolved in these task-specific ionic liquids can result in compounds with promising magnetic properties. In conclusion, we have shown that the scope of ionic liquids and its applications can be significantly enriched by incorporating functional groups. It has been demonstrated that structure determinations and DFT calculations can help to get more insight into the chemistry of functionalized ionic liquids. Metal-containing ionic liquids provide interesting new characteristics for new synthetic pathways concerning e.g. a ‘low-temperature’ solid state chemistry or crystal engineering from ionic liquids. The ionic liquids based on non-toxic ions proof that it is possible to obtain bio-compatible materials. The results presented reveal that task-specific ionic liquids can serve as a versatile and promising ‘toolbox’ for inorganic chemistry. Afdeling Moleculair Design en Synthese Departement Chemie Faculteit Wetenschappen Doctoral thesis Doctoraatsthesis
    01/2007;
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    ABSTRACT: Cyclic voltammetry and absorption spectrophotometry were used to examine the complex formation of cobalt (II) in the ionic liquids 1-butyl-3-methylimidazolium chloride and 1-butyl-3- methylimidazolium bis (trifluoromethylsulfonyl) imide. In, cobalt (II) is complexed as at ...
    01/2007;
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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. · 3.61 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. · 10.68 Impact Factor