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Papers by Verlaine Fossog
Analytical chemistry, Jan 19, 2016
High resolution mass spectrometry was utilized to study the highly complex product mixtures resul... more High resolution mass spectrometry was utilized to study the highly complex product mixtures resulting from electrochemical breakdown of lignin. As most of the chemical structures of the degradation products were unknown, enhanced mass defect filtering techniques were implemented to simplify the characterization of the mixtures. It was shown that the implemented ionization techniques had a major impact on the range of detectable breakdown products, with atmospheric pressure photoionization in negative ionization mode providing the widest coverage in our experiments. Different modified Kendrick mass plots were used as a basis for mass defect filtering, where Kendrick mass defect and the mass defect of the lignin-specific guaiacol (C7H7O2) monomeric unit were utilized, readily allowing class assignments independent of the oligomeric state of the product. The enhanced mass defect filtering strategy therefore provided rapid characterization of the sample composition. In addition, the str...
The journal of physical chemistry. B, Jan 20, 2015
Quasielastic neutron scattering (QENS) in combination with deuterium labeling allows for studying... more Quasielastic neutron scattering (QENS) in combination with deuterium labeling allows for studying protonated "highlighted" species and extracting detailed information about tangled stochastic processes. This approach has been applied to examine proton dynamics in the protic ionic liquid, triethylammonium triflate. The temperature range covered during the experiments (2-440 K) included two melting transitions correspondingly reflected in the global and localized dynamics of the cation. To focus on the dynamics of the acidic proton, QENS spectra of the sample with the deuterated alkyl side chains were analyzed. The remaining hydrogen atom served as a tagged particle for investigating both global long-range motion of the cation and specific dynamics of the proton and, thus, provided insight into the transport properties of triethylammonium triflate, which is important for designing electrochemical devices.
ChemPhysChem, 2014
The cation-anion and cation-solvent interactions in solutions of the protic ionic liquid (PIL) [E... more The cation-anion and cation-solvent interactions in solutions of the protic ionic liquid (PIL) [Et3NH][I] dissolved in solvents of different polarities are studied by means of far infrared vibrational (FIR) spectroscopy and density functional theory (DFT) calculations. The dissociation of contact ion pairs (CIPs) and the resulting formation of solvent-separated ion pairs (SIPs) can be observed and analyzed as a function of solvent concentration, solvent polarity, and temperature. In apolar environments, the CIPs dominate for all solvent concentrations and temperatures. At high concentrations of polar solvents, SIPs are favored over CIPs. For these PIL/solvent mixtures, CIPs are reformed by increasing the temperature due to the reduced polarity of the solvent. Overall, this approach provides equilibrium constants, free energies, enthalpies, and entropies for ion-pair formation in trialkylammonium-containing PILs. These results have important implications for the understanding of solvation chemistry and the reactivity of ionic liquids.
Angewandte Chemie, 2015
Die einzigartigen Eigenschaften ionischer Flüssigkeiten werden durch ein fein austariertes Energi... more Die einzigartigen Eigenschaften ionischer Flüssigkeiten werden durch ein fein austariertes Energiegleichgewicht zwischen Coulomb-Wechselwirkungen, Wasserstoffbrücken und Dispersionskräften bestimmt. Wir kçnnen innerhalb einer sorgfältig gewählten Zusammenstellung protischer ionischer Flüssigkeiten (PILs) mit Trialkylammonium-Kationen und Methylsulfonat-bzw. Triflat-Anionen in der PIL [(C 6 H 13 ) 3 NH][CF 3 SO 3 ] einen Übergang von H-Brücken-dominierter zu dispersionsdominierter Wechselwirkung beobachten. Die charakteristischen Merkmale der Schwingungen beider Ionenpaarspezies kçnnen in den Ferninfrarotspektren zweifelsfrei detektiert und zugeordnet werden. Das temperaturabhängige Gleichgewicht beider Spezies liefert die Enthalpie des Übergangs von der H-Brücken-zur dispersionsdominierten Spezies. Diese Vorgehensweise ermçglicht direkten Zugang zur relativen Stärke von H-Brücken und Dispersionskräften in einem Coulomb-dominierten System. Dispersionskorrigierte Dichtefunktionalrechnungen stützen das experimentelle Ergebnis, dass der Übergang zwischen nicht kovalent gebundenen Spezies nur dann erfolgt, wenn die H-Brücke zwischen Kation und Anion wie beim Triflat-Anion ausreichend schwach ist und gleichzeitig die Dispersionskräfte groß genug sind, wie es hier durch die drei Hexylgruppen des [(C 6 H 13 ) 3 NH]-Kations gewährleistet wird. Die Dispersionskräfte tragen quantitativ etwa 2.3 kJ mol À1 pro zusätzlicher Methylengruppe in den Ammonium-Kationen bei.
Journal of the Physical Society of Japan, 2013
Journal of Molecular Liquids, 2014
Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the ... more Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the present work we subsume our results on pyridinium-based ionic liquids. We have performed inelastic, quasielastic and elastic. Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the present work we subsume our work on pyridinium-based ionic liquids. We have performed inelastic, quasielastic and elastic neutron scattering experiments aiming to understand the different dynamical processes that occur at different temperatures in ionic liquids. Using quasielastic scattering we obtained data that can be described as a superposition of localized dynamical processes and long range diffusion. The localized processes, which originate from the alkyl chain and the pyridinium ring of the cation, have been modelled in terms of the so-called Gaussian model. The influence of the length of the alkyl chain, attached to the cation, on the dynamical processes is discussed in detail. Furthermore we show neutron backscattering data, obtained on partially deuterated samples, that clearly demonstrate the melting of the alkyl chain and the activation of methyl end-group rotations at low temperatures. Finally, the power of deuterium labelling is evidenced for inelastic neutron scattering data.
Angewandte Chemie, 2013
ABSTRACT Polarität kontrolliert die Gleichgewichtskonstanten und Freien Enthalpien von Kontaktion... more ABSTRACT Polarität kontrolliert die Gleichgewichtskonstanten und Freien Enthalpien von Kontaktionenpaaren (CIP) und solvensseparierten Ionenpaaren (SIP) in Mischungen von protischen ionischen Flüssigkeiten und molekularen Lösungsmitteln. Durch Ferninfrarotdifferenzspektren und zugehörige DFT‐berechnete Eigenschaften wird das subtile Gleichgewicht zwischen den Ionenspezies in Lösungsmitteln niedriger und hoher Polarität und unterschiedlicher Konzentration untersucht.
Angewandte Chemie International Edition, 2013
Polarity controls the equilibrium constants and free energies of contact ion pairs (CIPs) and sol... more Polarity controls the equilibrium constants and free energies of contact ion pairs (CIPs) and solvent-separated ion pairs (SIPs) in mixtures of protic ionic liquids and molecular solvents. The subtle balance between the ionic species was studied by far-infrared difference spectra and related DFT-calculated properties for solvents of low and high polarity and for different solvent concentrations.
Angewandte Chemie International Edition, 2013
Angewandte Chemie International Edition, 2015
The properties of ionic liquids are determined by the energy-balance between Coulomb-interaction,... more The properties of ionic liquids are determined by the energy-balance between Coulomb-interaction, hydrogenbonding, and dispersion forces. Out of a set of protic ionic liquids (PILs), including trialkylammonium cations and methylsulfonate and triflate anions we could detect the transfer from hydrogen-bonding to dispersion-dominated interaction between cation and anion in the PIL [(C 6 H 13 ) 3 NH][CF 3 SO 3 ]. The characteristic vibrational features for both ion-pair species can be detected and assigned in the far-infrared spectra. Our approach gives direct access to the relative strength of hydrogen-bonding and dispersion forces in a Coulomb-dominated system. Dispersion-corrected density functional theory (DFT) calculations support the experimental findings. The dispersion forces could be quantified to contribute about 2.3 kJ mol À1 per additional methylene group in the alkyl chains of the ammonium cation.
Analytical chemistry, Jan 19, 2016
High resolution mass spectrometry was utilized to study the highly complex product mixtures resul... more High resolution mass spectrometry was utilized to study the highly complex product mixtures resulting from electrochemical breakdown of lignin. As most of the chemical structures of the degradation products were unknown, enhanced mass defect filtering techniques were implemented to simplify the characterization of the mixtures. It was shown that the implemented ionization techniques had a major impact on the range of detectable breakdown products, with atmospheric pressure photoionization in negative ionization mode providing the widest coverage in our experiments. Different modified Kendrick mass plots were used as a basis for mass defect filtering, where Kendrick mass defect and the mass defect of the lignin-specific guaiacol (C7H7O2) monomeric unit were utilized, readily allowing class assignments independent of the oligomeric state of the product. The enhanced mass defect filtering strategy therefore provided rapid characterization of the sample composition. In addition, the str...
The journal of physical chemistry. B, Jan 20, 2015
Quasielastic neutron scattering (QENS) in combination with deuterium labeling allows for studying... more Quasielastic neutron scattering (QENS) in combination with deuterium labeling allows for studying protonated "highlighted" species and extracting detailed information about tangled stochastic processes. This approach has been applied to examine proton dynamics in the protic ionic liquid, triethylammonium triflate. The temperature range covered during the experiments (2-440 K) included two melting transitions correspondingly reflected in the global and localized dynamics of the cation. To focus on the dynamics of the acidic proton, QENS spectra of the sample with the deuterated alkyl side chains were analyzed. The remaining hydrogen atom served as a tagged particle for investigating both global long-range motion of the cation and specific dynamics of the proton and, thus, provided insight into the transport properties of triethylammonium triflate, which is important for designing electrochemical devices.
ChemPhysChem, 2014
The cation-anion and cation-solvent interactions in solutions of the protic ionic liquid (PIL) [E... more The cation-anion and cation-solvent interactions in solutions of the protic ionic liquid (PIL) [Et3NH][I] dissolved in solvents of different polarities are studied by means of far infrared vibrational (FIR) spectroscopy and density functional theory (DFT) calculations. The dissociation of contact ion pairs (CIPs) and the resulting formation of solvent-separated ion pairs (SIPs) can be observed and analyzed as a function of solvent concentration, solvent polarity, and temperature. In apolar environments, the CIPs dominate for all solvent concentrations and temperatures. At high concentrations of polar solvents, SIPs are favored over CIPs. For these PIL/solvent mixtures, CIPs are reformed by increasing the temperature due to the reduced polarity of the solvent. Overall, this approach provides equilibrium constants, free energies, enthalpies, and entropies for ion-pair formation in trialkylammonium-containing PILs. These results have important implications for the understanding of solvation chemistry and the reactivity of ionic liquids.
Angewandte Chemie, 2015
Die einzigartigen Eigenschaften ionischer Flüssigkeiten werden durch ein fein austariertes Energi... more Die einzigartigen Eigenschaften ionischer Flüssigkeiten werden durch ein fein austariertes Energiegleichgewicht zwischen Coulomb-Wechselwirkungen, Wasserstoffbrücken und Dispersionskräften bestimmt. Wir kçnnen innerhalb einer sorgfältig gewählten Zusammenstellung protischer ionischer Flüssigkeiten (PILs) mit Trialkylammonium-Kationen und Methylsulfonat-bzw. Triflat-Anionen in der PIL [(C 6 H 13 ) 3 NH][CF 3 SO 3 ] einen Übergang von H-Brücken-dominierter zu dispersionsdominierter Wechselwirkung beobachten. Die charakteristischen Merkmale der Schwingungen beider Ionenpaarspezies kçnnen in den Ferninfrarotspektren zweifelsfrei detektiert und zugeordnet werden. Das temperaturabhängige Gleichgewicht beider Spezies liefert die Enthalpie des Übergangs von der H-Brücken-zur dispersionsdominierten Spezies. Diese Vorgehensweise ermçglicht direkten Zugang zur relativen Stärke von H-Brücken und Dispersionskräften in einem Coulomb-dominierten System. Dispersionskorrigierte Dichtefunktionalrechnungen stützen das experimentelle Ergebnis, dass der Übergang zwischen nicht kovalent gebundenen Spezies nur dann erfolgt, wenn die H-Brücke zwischen Kation und Anion wie beim Triflat-Anion ausreichend schwach ist und gleichzeitig die Dispersionskräfte groß genug sind, wie es hier durch die drei Hexylgruppen des [(C 6 H 13 ) 3 NH]-Kations gewährleistet wird. Die Dispersionskräfte tragen quantitativ etwa 2.3 kJ mol À1 pro zusätzlicher Methylengruppe in den Ammonium-Kationen bei.
Journal of the Physical Society of Japan, 2013
Journal of Molecular Liquids, 2014
Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the ... more Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the present work we subsume our results on pyridinium-based ionic liquids. We have performed inelastic, quasielastic and elastic. Neutron scattering is an excellent tool to study the dynamics of hydrogen-rich materials. In the present work we subsume our work on pyridinium-based ionic liquids. We have performed inelastic, quasielastic and elastic neutron scattering experiments aiming to understand the different dynamical processes that occur at different temperatures in ionic liquids. Using quasielastic scattering we obtained data that can be described as a superposition of localized dynamical processes and long range diffusion. The localized processes, which originate from the alkyl chain and the pyridinium ring of the cation, have been modelled in terms of the so-called Gaussian model. The influence of the length of the alkyl chain, attached to the cation, on the dynamical processes is discussed in detail. Furthermore we show neutron backscattering data, obtained on partially deuterated samples, that clearly demonstrate the melting of the alkyl chain and the activation of methyl end-group rotations at low temperatures. Finally, the power of deuterium labelling is evidenced for inelastic neutron scattering data.
Angewandte Chemie, 2013
ABSTRACT Polarität kontrolliert die Gleichgewichtskonstanten und Freien Enthalpien von Kontaktion... more ABSTRACT Polarität kontrolliert die Gleichgewichtskonstanten und Freien Enthalpien von Kontaktionenpaaren (CIP) und solvensseparierten Ionenpaaren (SIP) in Mischungen von protischen ionischen Flüssigkeiten und molekularen Lösungsmitteln. Durch Ferninfrarotdifferenzspektren und zugehörige DFT‐berechnete Eigenschaften wird das subtile Gleichgewicht zwischen den Ionenspezies in Lösungsmitteln niedriger und hoher Polarität und unterschiedlicher Konzentration untersucht.
Angewandte Chemie International Edition, 2013
Polarity controls the equilibrium constants and free energies of contact ion pairs (CIPs) and sol... more Polarity controls the equilibrium constants and free energies of contact ion pairs (CIPs) and solvent-separated ion pairs (SIPs) in mixtures of protic ionic liquids and molecular solvents. The subtle balance between the ionic species was studied by far-infrared difference spectra and related DFT-calculated properties for solvents of low and high polarity and for different solvent concentrations.
Angewandte Chemie International Edition, 2013
Angewandte Chemie International Edition, 2015
The properties of ionic liquids are determined by the energy-balance between Coulomb-interaction,... more The properties of ionic liquids are determined by the energy-balance between Coulomb-interaction, hydrogenbonding, and dispersion forces. Out of a set of protic ionic liquids (PILs), including trialkylammonium cations and methylsulfonate and triflate anions we could detect the transfer from hydrogen-bonding to dispersion-dominated interaction between cation and anion in the PIL [(C 6 H 13 ) 3 NH][CF 3 SO 3 ]. The characteristic vibrational features for both ion-pair species can be detected and assigned in the far-infrared spectra. Our approach gives direct access to the relative strength of hydrogen-bonding and dispersion forces in a Coulomb-dominated system. Dispersion-corrected density functional theory (DFT) calculations support the experimental findings. The dispersion forces could be quantified to contribute about 2.3 kJ mol À1 per additional methylene group in the alkyl chains of the ammonium cation.