Photochemistry of an Anti-Bredt Olefin through the Lens of Multistate Multireference Quantum Chemistry

In 2024, Garg and co-workers reported that norborn-1-enes, a class of anti-Bredt olefins, can be systematically prepared and trapped. This finding has prompted us to combine multistate, multiconfigurational quantum chemical gradients and multiscale modeling to simulate the light-induced dynamics and chemistry of norborn-1-ene in acetonitrile. The results predict the existence of an excited state intermediate with a unique electronic structure consisting of a zwitterion incorporating a nonclassical cationic moiety. A set of 200 room-temperature quantum-classical trajectories were propagated to show that such intermediate decay through a unique conical intersection leads to the simultaneous formation of a carbene and a diradical as primary photoproducts. A third zwitterionic photoproduct is instead predicted to have a transient existence. Thus, our simulation not only uncovers a new type of photochemical funnel but also points to novel chemistries only accessible when anti-Bredt olefins are prepared or trapped under illumination conditions.