Synthesis and properties of novel type I photosensitizer polycyclic amide

Herein, we have designed and synthesized a novel type-I photosensitizer (PhPA) via Rh-catalyzed oxidative cyclization of diacetoxyterephthalamide with alkynes. The photoelectric properties, photosensitivity and photodegradation process of PhPA have been systematically investigated. The remarkable fluorescence quenching effect (Φ(PL) < 0.01) of PhPA suggests that the intersystem crossing from the singlet excited state to the reactive triplet state is enhanced by the enlarged conjugated backbone. Additionally, the ability of superoxide radical (O(2)(−)˙) generation was confirmed by electron paramagnetic resonance spectroscopy. Finally, the mechanism of PhPA photo-oxidative degradation via the structure of two metabolites is proposed.