Supramolecular packing dominant photocatalytic oxidation and anticancer performance of PDI

The development of organic supramolecular photocatalytic materials requires a deeper understanding of the structure-activity relationship. Herein, the effects of H/J-type stacking on the photocatalytic mechanism and activity of PDI have been investigated. As a face-to-face arrangement, H-aggregates have higher π-electron conjugation and show more semiconductor characteristics, which results in higher carrier separation and migration efficiency under irradiation. Whereas, J-aggregates exhibit more molecular properties due to its low π-electron conjugation caused by head-to-tail stacking mode. As a result, H-aggregated PDI mainly forms superoxide radicals (O2−) and holes (h+) through electron-transfer (ET). In contrast, J-aggregated PDI mainly generates singlet oxygen species (1O2) via energy-transfer (EnT). Benefit from the stronger oxidizability of O2− and h+, H-aggregated PDI shows higher photocatalytic activity for small molecule degradation and oxygen evolution under visible light. Whereas, J-aggregated PDI exhibits potential application in photocatalytic anti-cancer treatment owing to its high 1O2 quantum yields (0.66) under red light radiation. Our findings may provide a guidance for the development of supramolecular organic photocatalytic materials.