Ultrafast Photochemical Pericyclic Reactions and Isomerizations of Small Polyenes

摘要

Potential energy surfaces for pericyclic reactions can easily be predicted by means of correlation diagrams. Whereas the initially excited state (called 1 B in this paper) may vary from molecule to molecule, its population Is collected by a lower, dark state (2 A) of always the same nature, which corresponds to a two-electron excitation. From there, the system leaves to the ground states of educt and product(s) via a conical intersection (CI). Using Transient absorption and transient ionization spectroscopy, we measured the lifetimes t_1B and T_2A of these states After initiating electrocyclic ring opening of 1, 3-cyclohexadiene and some of its derivatives (α-terpinene, α- Phellandrene and 7-dehydrocholesterol).