Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory
| Autor: | Evgenii Titov, Peter Saalfrank, Clemens Rietze, Steven Lindner |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Arrhenius equation
Work (thermodynamics) 010304 chemical physics Chemistry Thermodynamics Context (language use) 010402 general chemistry Condensed Matter Physics Photochemistry 01 natural sciences 0104 chemical sciences Transition state theory symbols.namesake 0103 physical sciences symbols Institut für Chemie Molecule General Materials Science Density functional theory Wave function Isomerization |
| Zdroj: | Journal of physics. Condensed matter : an Institute of Physics journal. 29(31) |
| ISSN: | 1361-648X |
| Popis: | The thermal [Formula: see text] (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model-[Formula: see text] isomerization in azobenzene-a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the [Formula: see text] (back-)isomerization of azobenzenes under solvent-free conditions. |
| Databáze: | OpenAIRE |
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