This paper reports a novel method for the photoreduction of aryl bromides/chlorides using 656 nm LED light via a triplet-triplet annihilation (TTA) strategy. The method utilizes perylene as a metal-free photocatalyst, eliminating the need for electron sacrificial agents. A red light-absorbing photosensitizer, meso-tetraphenyl-tetrabenzoporphine Palladium complex (PdTPBP), is introduced to enable long-wavelength red light activation. Restricting the rotational freedom of the phenyl moiety in perylene derivatives enhances TTA efficiency and improves the photoreduction yield, even in large-scale reactions.

Le Zeng, Ling Huang, Wenhai Lin, Lin-Han Jiang, Gang Han