Substituent effects on dynamics at conical intersections: cycloheptatrienes
| Autor: | Andreas N. Unterreiner, Albert Stolow, Michael S. Schuurman, Oliver Schalk, Anna Wrona-Piotrowicz, Rasmus Y. Brogaard, Andrey E. Boguslavskiy, Nick Henry Werstiuk |
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| Rok vydání: | 2013 |
| Předmět: |
Wave packet
Electrons Electron Unsaturated hydrocarbons Photochemistry Molecular physics Vibration Delocalized electron chemistry.chemical_compound Wave packets Non-adiabatic dynamics Physical and Theoretical Chemistry Physics::Chemical Physics Cycloheptanes Anisotropy Computer Science::Distributed Parallel and Cluster Computing Vibrational dynamics Time-resolved photoelectron spectroscopy Conical intersection Photoelectron Spectroscopy Excited states Cycloheptatriene Conical surface Large-amplitude motion Dynamics Kinetics chemistry Excited state Photoelectron anisotropy Quantum Theory Thermodynamics Non-adiabatic transitions Quantum chemistry Electronic density |
| Zdroj: | The journal of physical chemistry. A. 117(40) |
| ISSN: | 1520-5215 |
| Popis: | Using selective methyl substitution, we study the effects of vibrational dynamics at conical intersections in unsaturated hydrocarbons. Here, we investigate the excited state nonadiabatic dynamics of cycloheptatriene (CHT) and its relation to dynamics in other polyenes by comparing CHT with 7-methyl CHT, 7-ethyl CHT, and perdeuterated CHT using time-resolved photoelectron spectroscopy and photoelectron anisotropy. Our results suggest that, upon ππ*-excitation to the bright 2A" state, we observe an early intersection with the dark 2A' state close to the Franck-Condon region with evidence of wavepacket bifurcation. This indicates that the wavepacket evolves on both states, likely along a planarization coordinate, with the majority of the flux undergoing nonadiabatic transition via conical intersections within 100 fs following light absorption. In CHT, large amplitude motion along the planarization coordinate improves the intra-ring π-overlap, yielding a delocalized electronic density. However, substitutions in 7 position, chosen to modify the inertia of the planarization motion, did not markedly alter the first step in the sequential kinetic scheme. This suggests that there is a crossing of potential energy surfaces before planarization is achieved and, thus, nonadiabatic transition likely takes place far away from a local minimum. |
| Databáze: | OpenAIRE |
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