Water adsorption on a liquid surface

Lovelock, Kevin R. J.; Smith, Emily F.; Deyko, Alexey; Villar‐García, Ignacio J.; Licence, Peter; Jones, Robert G.

doi:10.1039/b711680b

Cited by 76 publications

(114 citation statements)

References 12 publications

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“…Structure Name Altogether, we will show that 1) the nature of the anion has a strong influence on the positive charge of the imidazolium ring, 2) that the absolute value of the positive charge on the imidazolium ring is hardly influenced by hydrogenbonding interactions between anion and cation and 3) that the nature of the anion presumably modifies the degree of hybridisation in the imidazolium ring in case of the [C 8 [39,41,46,50,51,67] The XPS intensities of all ILs correspond within the margins of error with the nominal IL compositions confirming the high purity of the samples. Values for the elemental composition and BE values for all relevant core levels of all ILs are provided in Tables S1 and S2 in the Supporting Information.…”

Section: Chemical Formulamentioning

confidence: 74%

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Cremer

Kolbeck

Lovelock

et al. 2010

Chemistry A European J

273

335

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Ten [C(8)C(1)Im](+) (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl(-), Br(-), I(-), [NO(3)](-), [BF(4)](-), [TfO](-), [PF(6)](-), [Tf(2)N](-), [Pf(2)N](-), and [FAP](-) (TfO=trifluoromethylsulfonate, Tf(2)N=bis(trifluoromethylsulfonyl)imide, Pf(2)N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C(8)C(1)C(1)Im](+) (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br(-) and [Tf(2)N](-) were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While (1)H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C(2) position and the anion, a comparative XPS study provides first direct experimental evidence for cation-anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C(8)C(1)Im](+) and [C(8)C(1)C(1)Im](+) salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.

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Section: Chemical Formulamentioning

confidence: 74%

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Cremer

Kolbeck

Lovelock

et al. 2010

Chemistry A European J

273

335

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“…The first studies by AR-XPS demonstrated that the adsorption and wetting behaviour strongly depend on the particular combination of IL and support, with a strong influence of contaminations [150,156,192]. Furthermore, it was demonstrated that XPS can be also used to study reactions in ILs or at ILsubstrate or IL-electrode interfaces in situ, as a function of time or temperature [148,161,162,173,[193][194][195][196][197][198][199][200].…”

Section: Molecular Insights Into Il/gas and Il/support Interfacesmentioning

confidence: 99%

“…This was due to the high vapour pressures of common liquids or solvents, which are not compatible with the required UHV conditions. It was only recently realized that the situation is very different, when studying reactions in ILs, which have an inherently low vapour pressure, and first studies have been performed within the last years [148,161,162,173,[193][194][195][196][197][198][199][200]. Compared to classical spectroscopy techniques used to monitor chemical reactions, the advantage of XPS is that through the analysis of their core levels all relevant elements can be quantified and their chemical state can be analysed under well-defined (ultraclean) conditions.…”

Section: In Situ Reaction Monitoringmentioning

confidence: 99%

Ionic Liquids in Catalysis

2014

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Ionic liquids (ILs), salts with melting points below 100°C, represent a fascinating class of liquid materials typically characterized by an extremely low vapor pressure. Besides their application as new solvents or as electrolytes for electrochemical purposes, there are two important concepts of using ILs in catalysis: Liquid-liquid biphasic catalysis and IL thin film catalysis. Liquid-liquid biphasic catalysis enables either a very efficient manner to apply catalytic ILs, e.g. in Friedel-Crafts reactions, or to apply ionic transition metal catalyst solutions. In both cases, phase separation after reaction allows an easy separation of reaction products and catalyst re-use. One problem of liquidliquid biphasic catalysis is mass transfer limitation. If the chemical reaction is much faster than the liquid-liquid mass transfer the latter limits the overall reaction rate. This problem is overcome in IL thin film catalysis where diffusion pathways and thus the characteristic time of diffusion are short. Here, Supported Ionic Liquid Phase (SILP) and Solid Catalyst with Ionic Liquid Layer (SCILL) are the two most important concepts. In both, a high surface area solid substrate is covered with a thin IL film, which contains either a homogeneously dissolved transition metal complex for SILP, or which modifies catalytically active surface sites at the support for SCILL. In each concept, interface phenomena play a very important role: These may concern the interface of an IL phase with an organic phase in the case of liquidliquid biphasic catalysis. For IL thin film catalysis, the interfaces of the IL with the gas phase and with catalytic nanoparticles and/or support materials are of critical importance. It has recently been demonstrated that these interfaces and also the bulk of ILs can be investigated in great detail using surface science studies, which greatly contributed to the fundamental understanding of the catalytic properties of ILs and supported IL materials. Exemplary results concerning the IL/vacuum or IL/gas interface, the solubility and surface enrichment of dissolved metal complexes, the IL/support interface and the in situ monitoring of chemical reactions in ILs are presented.

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“…13,20,22 However, in a temperature dependent XPS study of D 2 O adsorption on the surface of [OMIm]BF 4 Lovelock et al described a new component in the N1s region with a binding energy 2.6 eV below the initial N1s component. 21 This component is attributed to products of beam damage and the chemical shift corresponds to nitrogen in an uncharged state. Kolbeck et al observed spectral changes in their XPS measurements for many [OMIm]-based ILs after extended exposure to X-rays.…”

Section: This Journal Is C the Owner Societies 2011mentioning

confidence: 99%

Changes of the near-surface chemical composition of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room temperature ionic liquid under the influence of irradiation

Keppler

Himmerlich

Ikari

et al. 2011

Phys. Chem. Chem. Phys.

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"This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively." Keppler, Angela; Himmerlich, Marcel; Ikari, Tomonori; Marschewski, Marcel; Pachomow, Evgenij; Höfft, Oliver; Maus-Friedrichs, Wolfgang; Endres, Frank; Krischok, Stefan Radiation induced degradation effects are studied for a model ionic liquid (IL) - [EMIm]Tf 2 N -in order to distinguish in which way the results of X-ray based material analysis methods can be falsified by the radiation supplied by typical X-ray sources itself. Photoelectron spectroscopy is commonly used for determining the electronic structure of ionic liquids. Degradation effects, which often occur e.g. in organic materials during X-ray or electron irradiation, are potentially critical for the interpretation of data obtained from ionic liquids. The changes of the chemical composition as well as the radiation-induced desorption of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm]Tf 2 N) fragments are analysed by X-ray photoelectron spectroscopy (XPS) as well as quadrupole mass spectroscopy (QMS) upon exposure to monochromated or non-monochromated AlKa X-rays from typical laboratory sources. During the irradiation of [EMIm]Tf 2 N, an increasing carbon concentration is observed in both cases and especially the [Tf 2 N] À ion is strongly altered. This observation is supported by the results from the QMS analysis which revealed a variety of different IL fragments that are desorbed during X-ray irradiation. It is shown that the decomposition rate is directly linked to the photon flux on the sample and hence has to be considered when planning an XPS experiment. However, for typical experiments on this particular IL the measurements suggest that the changes are on a larger time scale as typically required for spectra acquisition, in particular if monochromated X-ray sources are used.

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Water adsorption on a liquid surface

Abstract: Monolayer adsorption of water onto an ionic liquid in ultra-high vacuum has been demonstrated, revealing a heat of adsorption which exceeds the heat of absorption into the bulk liquid by approximately 40 kJ mol(-1).

Cited by 76 publications

References 12 publications

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Ionic Liquids in Catalysis

Changes of the near-surface chemical composition of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room temperature ionic liquid under the influence of irradiation

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