Controllable Multiemission with Ultralong Organic Phosphorescence in Crystal by Isomerization

Abstract Organic multiemissive materials with different lifetimes have attractive applications in sensors, bioimaging, data encryption, and so on. However, it is a formidable challenge to achieve multiemission with ultralong organic phosphorescence (UOP) in a single molecule. Here, reported is a series of isomers (o‐CzPh, m‐CzPh, and p‐CzPh) with multiemissive behavior under ambient conditions. All phosphors emit both fluorescence and UOP in crystal. Beyond that, o‐CzPh also displays thermally activated delayed fluorescence with a lifetime of 2.56 µs, which can be ascribed to the fast reverse intersystem crossing process from T₂ to S₁ states. Impressively, m‐CzPh crystal exhibits another phosphoresce emission with a lifetime of 0.24 ms assigned as single molecule phosphorescence, which is rarely reported. This finding enables the development of new organic phosphors with diverse lifetimes within a single molecule for potential applications.