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DDC: 540 × Subject: Thermodynamics ×

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Now showing 1 - 4 of 4
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    On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions
    (Weinheim : Wiley-VCH, 2019) Bläsing, Kevin; Labbow, Rene; Michalik, Dirk; Reiß, Fabian; Schul, Axel; Villinger, Alexander; Walker, Svenja
    Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me3Si)3E]+ (E=O, S), by reacting [Me3Si-H-SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si-E-SiMe3. In the reaction of Me3Si-O-SiMe3 with [Me3Si-H-SiMe3][B(C6F5)4], a ligand exchange was observed in the [Me3Si-H-SiMe3]+ cation leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion in a formal [Me2(H)Si]+ instead of the desired [Me3Si]+ transfer reaction. In contrast, the expected homoleptic persilylated [(Me3Si)3S]+ ion was formed and isolated as [B(C6F5)4]− and [CB]− salt, when Me3Si-S-SiMe3 was treated with either [Me3Si-H-SiMe3][B(C6F5)4] or Me3Si[CB]. However, the addition of Me3Si[CB] to Me3Si-O-SiMe3 unexpectedly led to the release of Me4Si with simultaneous formation of a cyclic dioxonium dication of the type [Me3Si-μO-SiMe2]2[CB]2 in an anion-mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me3Si)3E]+ and [(Me3Si)2(Me2(H)Si)E]+ ion formation are presented as well as mechanistic investigations on the template-driven transformation of the [(Me3Si)3E]+ ion into a cyclic dichalconium dication [Me3Si-μE-SiMe2]22+. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Femtosecond stimulated Raman spectroscopy of the cyclobutane thymine dimer repair mechanism: A computational study
    (Washington, DC : American Chemical Society, 2014) Ando, H.; Fingerhut, B.P.; Dorfman, K.E.; Biggs, J.D.; Mukamel, S.
    Cyclobutane thymine dimer, one of the major lesions in DNA formed by exposure to UV sunlight, is repaired in a photoreactivation process, which is essential to maintain life. The molecular mechanism of the central step, i.e., intradimer C-C bond splitting, still remains an open question. In a simulation study, we demonstrate how the time evolution of characteristic marker bands (C=O and C=C/C-C stretch vibrations) of cyclobutane thymine dimer and thymine dinucleotide radical anion, thymidylyl(3′→5′)-thymidine, can be directly probed with femtosecond stimulated Raman spectroscopy (FSRS). We construct a DFT(M05-2X) potential energy surface with two minor barriers for the intradimer C5-C′5 splitting and a main barrier for the C6-C′6 splitting, and identify the appearance of two C5=C6 stretch vibrations due to the C6-C′6 splitting as a spectroscopic signature of the underlying bond splitting mechanism. The sequential mechanism shows only absorptive features in the simulated FSRS signals, whereas the fast concerted mechanism shows characteristic dispersive line shapes. (Figure Presented).
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    A continuum model for yttria-stabilized zirconia incorporating triple phase boundary, lattice structure and immobile oxide ions
    (Berlin ; Heidelberg ; New York : Springer, 2019) Vágner, Petr; Guhlke, Clemens; Miloš, Vojtěch; Müller, Rüdiger; Fuhrmann, Jürgen
    A continuum model for yttria-stabilized zirconia (YSZ) in the framework of non-equilibrium thermodynamics is developed. Particular attention is given to (i) modeling of the YSZ-metal-gas triple phase boundary, (ii) incorporation of the lattice structure and immobile oxide ions within the free energy model and (iii) surface reactions. A finite volume discretization method based on modified Scharfetter-Gummel fluxes is derived in order to perform numerical simulations. The model is used to study the impact of yttria and immobile oxide ions on the structure of the charged boundary layer and the double layer capacitance. Cyclic voltammograms of an air-half cell are simulated to study the effect of parameter variations on surface reactions, adsorption and anion diffusion. © 2019, The Author(s).
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    Boundary conditions for electrochemical interfaces
    (Bristol : IOP Publishing, 2017) Landstorfer, Manuel
    Consistent boundary conditions for electrochemical interfaces, which cover double layer charging, pseudo-capacitive effects and transfer reactions, are of high demand in electrochemistry and adjacent disciplines. Mathematical modeling and optimization of electrochemical systems is a strongly emerging approach to reduce cost and increase efficiency of super-capacitors, batteries, fuel cells, and electro-catalysis. However, many mathematical models which are used to describe such systems lack a real predictive value. Origin of this shortcoming is the usage of oversimplified boundary conditions. In this work we derive the boundary conditions for some general electrode-electrolyte interface based on non-equilibrium thermodynamics for volumes and surfaces. The resulting equations are widely applicable and cover also tangential transport. The general framework is then applied to a specific material model which allows the deduction of a current-voltage relation and thus a comparison to experimental data. Some simplified 1D examples show the range of applicability of the new approach.