Department of Physics and Astronomy: Publications and Other Research

 

Document Type

Article

Date of this Version

5-18-2023

Citation

Nature Communications | ( 2023) 14:2795. https://doi.org/10.1038/s41467-023-38513-6

Comments

Open access.

Abstract

Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ and π bonds through a cyclic structure. This structure is known as a pericyclic transition state for thermal reactions and a pericyclic minimum in the excited state for photochemical reactions. However, the structure of the pericyclic geometry has yet to be observed experimentally.We use a combination of ultrafast electron diffraction and excited state wavepacket simulations to image structural dynamics through the pericyclic minimum of a photochemical electrocyclic ring-opening reaction in the molecule α-terpinene. The structural motion into the pericyclic minimum is dominated by rehybridization of two carbon atoms, which is required for the transformation from two to three conjugated π bonds. The σ bond dissociation largely happens after internal conversion from the pericyclicminimum to the electronic ground state. These findings may be transferrable to electrocyclic reactions in general.

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