1 research outputs found
Photochemical Ring-Opening Reaction of 1,3-Cyclohexadiene: Identifying the True Reactive State
The photochemically induced ring-opening isomerization
reaction
of 1,3-cyclohexadiene to 1,3,5-hexatriene is a textbook example of
a pericyclic reaction and has been amply investigated with advanced
spectroscopic techniques. The main open question has been the identification
of the single reactive state which drives the process. The generally
accepted description of the isomerization pathway starts with a valence
excitation to the lowest lying bright state, followed by a passage
through a conical intersection to the lowest lying doubly excited
state, and finally a branching between either the return to the ground
state of the cyclic molecule or the actual ring-opening reaction leading
to the open-chain isomer. Here, in a joint experimental and computational
effort, we demonstrate that the evolution of the excitation–deexcitation
process is much more complex than that usually described. In particular,
we show that an initially high-lying electronic state smoothly decreasing
in energy along the reaction path plays a key role in the ring-opening
reaction