Substituent effects on dynamics at conical intersections: Cycloheptatrienes

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DOIResolve DOI: http://doi.org/10.1021/jp309875m
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TypeArticle
Journal titleJournal of Physical Chemistry A
ISSN1089-5639
Volume117
Issue40
Pages1023910247; # of pages: 9
SubjectConical intersection; Large-amplitude motion; Non-adiabatic dynamics; Non-adiabatic transitions; Photoelectron anisotropy; Time-resolved photoelectron spectroscopy; Unsaturated hydrocarbons; Vibrational dynamics; Dynamics; Photoelectron spectroscopy; Quantum chemistry; Wave packets; Excited states
AbstractUsing 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.
Publication date
LanguageEnglish
AffiliationSecurity and Disruptive Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21270503
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Record identifier4838f116-1768-458c-9fef-1800e68b1bf9
Record created2014-02-14
Record modified2016-05-09
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