Modulating Room-Temperature Phosphorescence of Phenothiazine Dioxide via External Heavy Atoms

Developing pure organic materials with ultralong lifetimes and balanced quantum efficiency is attractive but challenging. In this study, we propose a novel strategy to investigate external heavy atoms by linking molecular emitters with halogen through a flexible alkyl chain. X-ray crystal analysis clearly reveal the halogen C-X-π interactions, which can be tuned by halogen donors, as well as the distance and geometry between them. Impressively, DOPTZ-C3Cl featuring a chloride atom as donor, exhibits a balanced long phosphorescence lifetime of 1351 ms and a phosphorescence quantum yield of 10.1 %. We also first demonstrate that Cl can induce more positive effect than heavier halogens (Br and I) on prolonging the lifetime. We envisage that the present study will expedite new molecular design to manipulate the room temperature phosphorescence via external heavy atom effect, and highlight a special C-Cl⋅⋅⋅π interaction for the development of ultralong phosphorescent materials.