Exploring the triplet state properties of thio-benzothioxanthene imides with applications in TTA-upconversion and photopolymerization.

Thio-benzothioxanthene imide (BTXI) exhibits long excited state lifetime ( τ T = 17.7 μs) and high ISC efficiency ( Φ Δ = 97%). For the first time, BTXI derivatives were used as photosensitizers for triplet-triplet annihilation upconversion, achieving the highest efficiency of 13.8%. In addition, thio-BTXI derivatives were used as photoinitiators for photopolymerization, resulting in a series of green light-activated radical polymerization systems.