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We studied the formation and surface behavior of Pt(II) and Pd(II) complexes with ligand systems derived from two nitrile-functionalized ionic liquids (ILs) in solution using angle-resolved X-ray photoelectron spectroscopy (ARXPS). These ligand systems enabled a high solubility of the metal complexes in IL solution. The complexes were prepared by simple ligand substitution under vacuum conditions in defined excess of the coordinating ILs, [C 3 CNC 1 Im][Tf 2 N] and [C 1 CNC 1 Pip][Tf 2 N], to immediately yield solutions of the final products. The ILs differ in the cationic head group and the chain length of the functionalized substituent. Our XPS measurements on the neat ILs gave insights in the electronic properties of the coordinating substituents revealing differences in donation capability and stability of the complexes. Investigations on the composition of the outermost surface layers using ARXPS revealed no surface affinity of the nitrile-functionalized chains in the neat ILs. Solutions of the formed complexes in the nitrile ILs showed homogeneous distribution of the solute at the surface with the heterocyclic moieties preferentially orientated towards the vacuum, while the metal centers are rather located further away from the IL/vacuum interface., (© 2022 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Mixing ionic liquids is a suitable strategy to tailor properties, e.g., to reduce melting points. The present study aims to widen the application range of low-toxic choline-based ionic liquids by studying eight binary phase diagrams of six different choline carboxylates. Five of them show eutectic points with melting points dropping by 13 to 45 °C. The eutectic mixtures of choline acetate and choline 2-methylbutarate were found to melt at 45 °C, which represents a remarkable melting point depression compared to the pure compounds with melting points of 81 (choline acetate) and 90 °C (choline 2-methylbutarate), respectively. Besides melting points, the thermal stabilities of the choline salt mixtures were investigated to define the thermal operation range for potential practical applications of these mixtures. Typical decomposition temperatures were found between 165 and 207 °C, with choline lactate exhibiting the highest thermal stability.

Ionic liquids (ILs) are promising solvents for gas separation processes such as carbon dioxide (CO2) capture from flue gases. For the design of corresponding processes and apparatus, thermophysical properties of ILs containing dissolved gases are required. In the present study, it is demonstrated that with a single optical setup, mutual and thermal diffusivities as well as refractive indices can be measured quasi-simultaneously for such mixtures. Dynamic light scattering (DLS) from bulk fluids was applied to determine mutual and thermal diffusivities for mixtures of 1-butyl-3-methylimidazolium tricyanomethanide ([BMIM][C(CN)3]) or 1-butyl-3-methylimidazolium tetracyanoborate ([BMIM][B(CN)4]) with dissolved CO2 at temperatures from 303.15 to 333.15 K and pressures between 2 and 26 bar in macroscopic thermodynamic equilibrium. Good agreement with literature data and only slight differences between the diffusivities measured for the two systems at the same temperature and comparable mole fractions of CO2 were found. Increasing mutual diffusivities with increasing mole fractions of CO2 are consistent with decreasing viscosities reported for other IL-CO2 mixtures in the literature and can be attributed to weakening of molecular interactions by the dissolved gas. For the conditions studied, no dependence of the thermal diffusivity on the temperature or the mole fraction of CO2 could be found.

New Brønsted acidic ionic liquids (BAILs) are prepared by treating zwitterions, which are composed of an imidazolium cation and a sulfonate anion, with an alkanedisulfonic acid. Acidification of the zwitterions produces the cation and deprotonation of the alkanedisulfonic acid forms the anion of the new BAILs. Direct laser desorption/ionisation (LDI), matrix-assisted LDI (MALDI) and electrospray ionisation (ESI) are employed to transfer ions into the gas-phase for detection by mass spectrometry and for dissociation studies by tandem mass spectrometry. The components of the BAILs are confirmed by LDI and MALDI by the detection of the respective cation and anion and by ESI by the observation of the cation and the dianion. A prominent feature of ESI is the formation of aggregates (cluster ions). Positively charged cluster ions are formally composed of multiple zwitterions plus one additional proton. In the negative-ion mode the clusters also incorporate the zwitterions which are, however, linked with the alkanedisulfonate dianion. In collision-induced dissociations (CID), the cationic aggregates show the evaporation of zwitterions until the protonated zwitterion is reached. Similarly, the cluster dianions release zwitterions until the free alkane disulfonate dianion is reached. However, the 1:1 adduct of dianion and zwitterion also displays proton transfer and Coulomb explosion into the mono-protonated disulfonic mono-anion and an imidazole-based carbene with sulfonate mono-anion., (This journal is © the Owner Societies 2012)

Homogeneous catalysis in room-temperature ionic liquids (ILs) constitutes a most interesting field of research with high potential in technical applications. As concerns the hydrogenation of unsaturated hydrocarbons, Wilkinson's compound RhCl(PPh(3))(3) represents a catalyst that provides high selectivity and activity. Herein, we demonstrate the application of infrared spectroscopy to the quantitative analysis of the Wilkinson catalyst in the IL 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). Our study demonstrates for the first time the quantitative, accurate and reproducible determination of the concentration of a rhodium catalyst by means of IR spectroscopy and, moreover, allows the investigation of intermolecular interactions. Spectral features, located mainly in the fingerprint region of the IR spectrum, are identified revealing the influence of the dissolved catalyst on the IL's vibrational structure. In particular, the ring-bending mode of the imidazolium ring shows a frequency shift as a function of catalyst concentration, probably due to hydrogen-bond formation between the IL cation and the Rh complex. The results show the potential of IR spectroscopy both for application as a quick process control technology in catalytic processes and as a tool for better understanding of IL-catalyst interactions.

The targeted enrichment of a Pt complex with an ionic liquid (IL)‐derived ligand system in IL solution is demonstrated by using angle‐resolved X‐ray photoelectron spectroscopy. When the ligand system is complemented with fluorinated side chains, the complex accumulates strongly at the IL/gas interface, while in an equivalent solution of a complex without these substituents no such effect could be observed. This buoy‐like behavior induces strong population of the complex at the outermost molecular layer close to surface saturation, which was studied over a range from 5 to 30 %mol. The surface enrichment was found to be most efficient at the lowest concentration, which is particularly favorable for catalytic applications such as supported ionic‐liquid‐phase (SILP) catalysis. [ABSTRACT FROM AUTHOR]

A new synthesis route for the zeolitic imidazolate framework ZIF-4 using imidazolium imidazolate is reported. Additionally, the ionic liquid-derived material is compared to conventional ZIF-4 with respect to the powder X-ray diffraction pattern pattern, nitrogen uptake, particle size, and separation potential for olefin/paraffin gas mixtures. Higher synthesis yields were obtained, and the different particle size affected the performance in the separation of ethane and ethylene. [ABSTRACT FROM AUTHOR]

Using ionic liquids (ILs) as linker precursors, the well‐known metal‐organic framework (MOF) UiO‐66 (Universitetet i Oslo) and the recently reported MOF hcp UiO‐66 (hexagonal closed packed) have been successfully synthesized and characterized. The advantage of the applied novel synthesis approach is an economically and environmentally benign work‐up procedure, due to the better solubility of the IL. Additionally, the reactivity of the terephthalate anions is increased compared to terephthalic acid, resulting in faster MOF formation with an increased amount of defects in the MOF structure. In order to explore to the influence of defects on the catalytic performance, the cyclisation of citronellal to isopulegol was employed as test reaction. The activity of hcp UiO‐66 and fcc UiO‐66 (face centered cubic) is improved compared to other MOF or zeolite based catalysts, while the selectivity is similar. [ABSTRACT FROM AUTHOR]

By using a terephthalate containing ionic liquid, a new metal–organic framework, hcp UiO-66, comprising (Zr12O8(OH)14) double clusters and terephthalate ligands has been synthesized. The hydrothermal synthesis of hcp UiO-66 might help to establish metal–organic frameworks for industrial scale applications. [ABSTRACT FROM AUTHOR]

Ionic liquids (IL) hold a great potential as novel electrolytes for applications in electronic materials and energy technology. The functionality of ILs in these applications relies on their interface to semiconducting nanomaterials. Therefore, methods to control the chemistry and structure of this interface are the key to assemble new IL-based electronic and electrochemical materials. Here, we present a new method to prepare a chemically well-defined interface between an oxide and an IL film. An imidazolium-based IL, which is carrying an ester group, is deposited onto cobalt oxide surface by evaporation. The IL binds covalently to the surface by thermally activated cleavage of the ester group and formation of a bridging carboxylate. The anchoring reaction shows high structure sensitivity, which implies that the IL film can be adhered selectively to specific oxide surfaces. [ABSTRACT FROM AUTHOR]

[EMIM][Hbdc] and [EMIM]2[bdc] were synthesized and successfully used in a one-step synthesis procedure of MIL-53(Al)/boehmite composites with unusual properties. The breathing effect typically observed for MIL-53(Al) is not found and scanning electron microscopy confirms the presence of MIL-53 nanoparticles in a boehmite matrix. The completely different characteristics of this MIL-53 samples in comparison to hydrothermally synthesized MIL-53(Al) clearly demonstrate the tremendous influence of variations of the reagents used for the syntheses of metal-organic framework materials. [ABSTRACT FROM AUTHOR]

An organic imidazolium salt of terephthalic acid has been utilized as a linker precursor for the synthesis of an aluminum-based metal organic framework (MOF) with MIL-53(ht) structure. This material shows the predicted porosity in terms of nitrogen and hydrogen sorption without exhibiting the breathing effect typical for MIL-53(Al) materials. [ABSTRACT FROM AUTHOR]

Keywords: catalysis; ionic liquids; surface analysis; surface enrichment; X-ray photoelectron spectroscopy (XPS) EN catalysis ionic liquids surface analysis surface enrichment X-ray photoelectron spectroscopy (XPS) 1 1 1 01/16/23 20230112 NES 230112 B Fluorinated side chains b of a functionalized Pt complex in an ionic liquid act as buoys, leading to pronounced enrichment of the complex at the IL/gas interface, as is evidenced by strongly enhanced Pt signals in angle-resolved photoelectron spectroscopy. Catalysis, ionic liquids, surface analysis, surface enrichment, X-ray photoelectron spectroscopy (XPS). [Extracted from the article]

A series of hexahalocerate(III) salts with the general formula [cation]3[CeHal6] have been prepared by dissolving anhydrous cerium trihalides in imidazolium halide ionic liquids. Complexes with different anions, [CeCl6]3-, [CeBr6]3- and [CeBr3Cl3]3-, were synthesized and their cationic alkyl chains were varied. To confirm the structures of the prepared salts, X-ray crystallography was used to characterize [BMIM]3[CeCl6]. Two different crystal structures were found: [BMIM]3[CeCl6] and the linear coordination polymer [BMIM] x[Ce(µ-Cl)2Cl2(EtOH)2] x containing coordinated solvent. All the synthesized compounds were characterized by DSC and TGA. The influence of the cationic and anionic structures on the melting points and decomposition temperatures is discussed. Furthermore, the Ce-containing salts [BMIM]3[CeHal6] show interesting photoluminescence properties: intense Ce3+-based 5d-4f-centred emission from the soft UV-B region to the border of visible light is observed that is driven both by direct excitation of Ce3+ as well as by a sensitizer effect of the [BMIM]+ cation. [ABSTRACT FROM AUTHOR]

Abstract: The relevant interactions between the organic ions of ionic liquids (ILs) include van der Waals forces, hydrogen bonding and coulombic interactions. In solutions these interactions lead to the formation of aggregates. Depending on the strength of the interactions and the concentration of the IL in the solvent, different aggregates are formed with ion-pairs being the dominant species at low concentrations. A probe for investigating these interactions is the enantioselectivity of a reaction carried out on a prochiral ion in presence of its chiral counter-ion. As asymmetric induction requires structurally well-defined interactions, the induced enantioselectivity can be correlated to ion aggregate formation. The first proof of this concept was provided by the asymmetric hydrogenation of [N-(3′-oxobutyl)-N-methylimidazolium]-[(R)-camphorsulfonate] and -[(S)-camphorsulfonate] using a heterogeneous Ru on C contact. Depending on the substrate IL concentration an enantioselectivity of up to 94% could be realized. The catalytic results were linked to the probability of the ion pair formation as evidenced by DOSY-NMR measurements and dielectric relaxation spectroscopy. The expansion of this principle to chiral ionic liquids that can be easily decomposed to chiral building blocks of synthetic relevance led us to the development of two approaches: a) the application of an IL substrate consisting of a chiral cation and a keto-functionalized, prochiral carboxylate counter-ion allowing for the synthesis of chiral esters in the sequence of IL hydrogenation and esterification; and b) reversible binding of a prochiral substrate to the cation of an IL with a chiral, enantiopure anion allowing the synthesis of neutral chiral building blocks in a sequence of binding, hydrogenation and splitting. The latter approach was tested for two ILs based on the hydroxyl-functionalized cation cholinium to which a prochiral keto functionalized carboxylic acids was reversibly attached via esterification. The hydrogenation of such prochiral ester cation in the presence of enantiopure anions resulted in ees of up to 63%. [Copyright &y& Elsevier]

A new method to synthesise long-chain and functionalised methylphosphonate esters and the corresponding ionic liquids is reported. The synthesis comprises the formation of dialkyl methylphosphonate esters in a SN2 reaction followed by the use of these esters as alkylating agents to form the corresponding, new alkyl methylphosphonate ILs. [ABSTRACT FROM AUTHOR]

Abstract: The diastereomeric ionic liquid (IL) (1R,2S)-ephedrinium (RS)-methoxytrifluorophenylacetate 1 was synthesized and its aggregation behavior and diastereomeric interaction were investigated using two independent methods. The aggregation number of the IL in methylene chloride was determined by diffusion ordered NMR spectroscopy. Furthermore the concentration dependence of the signal split of the two diastereomeric ILs (1R,2S)-ephedrinium (R)-methoxytrifluorophenylacetate and (1R,2S)-ephedrinium (S)-methoxytrifluorophenylacetate was measured and could be linked to the aggregation number. [Copyright &y& Elsevier]

Thermophysical properties of low-viscosity ionic liquids (ILs) based on the tetracyanoborate ([B(CN)4]−) anion carrying a homologous series of 1-alkyl-3-methylimidazolium ([AMIM]+) cations [EMIM]+ (ethyl), [BMIM]+ (butyl), [HMIM]+ (hexyl), [OMIM]+ (octyl), and [DMIM]+ (decyl) were investigated by experimental methods and molecular dynamics (MD) simulations at atmospheric pressure and various temperatures. Spectroscopic methods based on nuclear magnetic resonance and surface light scattering were applied to measure the ion self-diffusion coefficients and dynamic viscosity, respectively. In terms of MD simulations, a nonpolarizable molecular model for [EMIM][B(CN)4] developed by optimization to experimental data was transferred to the other homologous ILs. For the appropriate description of the inter- and intramolecular interactions, precise and approximate force fields (FFs) were tested regarding their transferability within the homologous IL series, aiming at reducing the computational effort in molecular simulations. It is shown that at comparable simulated and experimental densities, the calculated and measured data for viscosity and self-diffusion coefficients of the ILs agree well mostly within combined uncertainties, but deviate stronger for longer-chained ILs using an overly coarse FF model. For the [B(CN)4]−-based ILs studied, a comparison with literature data, the influence of varying alkyl chain length in the cation on their structural and thermophysical properties, and a correlation between self-diffusivity and viscosity are discussed. [ABSTRACT FROM AUTHOR]

Here we present novel CO2 sorbents based on chitosan ionogels. The powder sorbents called inverse supported ionic liquid phase (SILP) materials were prepared by dissolving chitosan in various ionic liquids (ILs) followed by encapsulation of the ionogel droplets with nanoporous fumed silica. CO2 absorption was determined at 40 °C in the range of 200 to 5500 mbar. At 1 bar, absorption capacities of these materials were 0.1-0.8 mol kg-1; at 5 bar, values of 0.2-1.5 mol kg-1 were reached. A comparison of inverse SILP materials with and without chitosan dissolved in the applied IL indicated that the presence of chitosan increased the CO2 absorption efficiency of the materials. The aim of the study was also to compare the CO2 absorption in pure chitosan and chitosan dissolved in ILs. It was found that dissolution increases the absorption capacity of chitosan about 10 times. [ABSTRACT FROM AUTHOR]

Abstract: Ion pairing in [N-(3′-oxohexyl)-N-methylimidazolium][(R)-mandelate] was probed as a function of its concentration in ethanol and compared to the corresponding [(S)-camphorsulfonate] ionic liquid. The applied methodologies comprised asymmetric hydrogenation with ee monitoring as well as independent diffusion-ordered NMR and conductivity measurements. [ABSTRACT FROM AUTHOR]

The separation of enantiomers remains a major challenge for the pharmaceutical industry. In this work, eight chiral ionic liquids (CILs) directly derived from the 'chiral pool' were synthesized and characterized in order to develop enantioselective systems, for the chiral resolution. According to their chiral cations, three different groups of CILs were prepared, namely based on quinine, l -proline and l -valine, and their enantiomeric recognition ability evaluated. For that purpose the diastereomeric interactions between a racemic mixture of Mosher's acid sodium salt and each CIL were studied using 19F NMR spectroscopy. The remarkable chemical shift dispersion induced by some CILs demonstrates their potential application in chiral resolution. Additionally the optical rotation, thermophysical properties and ecotoxicity against the marine bacteria Aliivibrio fischeri of these chiral ionic liquids were addressed. Unlabelled Image • Chiral ionic liquids derived from valine, proline and quinine are successfully prepared. • In general, these chiral compounds exhibit high thermal stability and low ecotoxicity. • Outstanding shift difference of racemic Mosher's acid carboxylate is observed. • Quinine-based compounds seem to be particularly promising for chiral resolution. [ABSTRACT FROM AUTHOR]

Thermochemical investigation of the series of 1-alkyl-3-methylimidazolium ionic liquids with B(CN) 4 and PF 2 (CN) 4 anions is presented. Absolute vapor pressures and vaporization enthalpies have been measured by using quartz-crystal microbalance. Gas-phase enthalpies of formation of ILs were calculated by using the high-level quantum-chemical method G3MP2. From a combination of experimental and theoretical results, the enthalpy of formation of aqueous B(CN) 4 ion was derived for the first time. [ABSTRACT FROM AUTHOR]

Abstract: An X-ray photoelectron spectroscopy (XPS) study of Pt(II) and Pt(IV) complexes dissolved in ionic liquids (ILs) revealed the occurrence of a rich redox chemistry, which is partly induced by X-ray radiation. Depending on the IL anion either a reduction of Pt(IV) to Pt(II) in the case of ethylsulfate ([EtOSO3]−)-based ILs, or an oxidation of Pt(II) to Pt(IV) in the case of bis[(trifluoromethyl)sulfonyl]imide ([Tf2N]−)-based ILs was observed upon X-ray irradiation. Moreover, surface enrichment or depletion effects of the Pt complexes were deduced from angle-resolved XPS (ARXPS) data; while the Pt complexes dissolved in imidazolium-based ILs tended to deplete from the surface, in pyrrolidinium-based solutions a surface enrichment of the Pt complexes was observed. [Copyright &y& Elsevier]

Carbon dioxide (CO2) absorption by the amine-functionalized ionic liquid (IL) dihydroxyethyl dimethylammonium taurinate at 310 K was studied using surface- and bulk-sensitive experimental techniques. From near-ambient pressure X-ray photoelectron spectroscopy at 0.9 mbar CO2, the amount of captured CO2 per mole of IL in the near-surface region is quantified to ~0.58 mol, with ~0.15 mol in form of carbamate dianions and ~0.43 mol in form of carbamic acid. From isothermal uptake experiments combined with infrared spectroscopy, CO2 is found to be bound in the bulk as carbamate (with nominally 0.5 mol of CO2 bound per 1 mol of IL) up to ~2.5 bar CO2, and as carbamic acid (with nominally 1 mol CO2 bound per 1 mol IL) at higher pressures. We attribute the fact that at low pressures carbamic acid is the dominating species in the near-surface region, while only carbamate is formed in the bulk, to differences in solvation in the outermost IL layers as compared to the bulk situation. [ABSTRACT FROM AUTHOR]

Inthe present study, the thermophysical properties of the tetracyanoborate-basedionic liquids (ILs) 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][B(CN)4]) and 1-hexyl-3-methylimidazolium tetracyanoborate ([HMIM][B(CN)4]) obtained by both experimental methods and molecular dynamics(MD) simulations are presented. Conventional experimental techniqueswere applied for the determination of refractive index, density, interfacialtension, and self-diffusion coefficients for [HMIM][B(CN)4] at atmospheric pressure in the temperature range from 283.15 to363.15 K. In addition, surface light scattering (SLS) experimentsprovided accurate viscosity and interfacial tension data. As no completemolecular parametrization was available for the MD simulations of[HMIM][B(CN)4], our recently developed united-atom forcefield for [EMIM][B(CN)4] was partially transferred to thehomologous IL [HMIM][B(CN)4]. Deviations between our simulatedand experimental data for the equilibrium properties are less than±0.3% in the case of density and less than ±8% in the caseof interfacial tension for both ILs. Furthermore, the calculated andmeasured data for the transport properties viscosity and self-diffusioncoefficient are in good agreement, with deviations of less than ±30%over the whole temperature range. In addition to a comparison withthe literature, the influence of varying cation chain length on thermophysicalproperties of [EMIM][B(CN)4] and [HMIM][B(CN)4] is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The technical relevant Pt-catalyzed hydrosilylation of allyl chloride with trichlorosilane was investigated in a monophasic reaction system containing an ionic liquid (IL) additive. ILs screening allowed us to identify the liquid 1-decyl-3-methylimidazolium bis(trifloromethanesulfonyl)amide ([DMIM][NTf2]) as the best additive for such process. This IL combined complete miscibility with reactants as long as chemical and thermal robustness. After the reaction, the hydrosilylation product (3-chloropropyl)trichlorosilane was distilled off and the residual IL/catalyst solution could be reused. In such a way, a final TON of 14,200 was achieved over 10 reaction/distillation cycles without any loss of catalytic activity. The ability of [DMIM][NTf2] to prevent catalyst decomposition was deeper investigated and it was found that even with a Pt loading as high as 9500ppm, the IL acted as protective/stabilizing agent for the catalyst during the thermally stressing product distillation. [Copyright &y& Elsevier]