immediately after photoexcited SET can serve as a deactivation pathway, the release of CO2 gas renders the fragmentation irreversible, driving the reaction forward. The alkyl radical R•, formed in situ, will then rapidly and selectively attack the electron poor aromatic phthalonitrile at the C4 site to form an aryl radical adduct (I1, ∆G = -2.7 kcal mol - ).