Uncovering Triradicaloid Structures in S₁ Benzene Photochemistry

Theoretical evidence concerning the multiradicaloid character in benzene photochemistry is reported based on a topological analysis of the correlated electron localization function. The bonding implications of triradicaloid conditions in both ground and excited states of S-1 benzene are discussed within the bonding evolution theory. Our results suggest that triradicaloid/biradicaloid structures form due to the non-bonding density concentration over C atoms, causing the distorted geometry near the S-1/S-0 crossing. Biradicaloid centers formed in the excited state trigger new CC bonds, leading to a variety of photoproducts.