Photochemical Ring-Opening Reaction of 1,3-Cyclohexadiene: the True Reactive State

• The photochemically induced ring-opening isomeriza-tion 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.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

resolved photoelectron-spectroscopy

initio molecular-dynamics

electronic-spectra

quantum dynamics

rydberg states

photodissociation

diarylethene

hexatriene

crystals

valence

Chemistry

Publication and Content Type

ref (subject category)

art (subject category)