Controllable Multiemission with Ultralong Organic Phosphorescence in Crystal by Isomerization

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.