Utilizing d–pπ Bonds for Ultralong Organic Phosphorescence

Developing pure organic materials with ultralong lifetimes is attractive but challenging. Here we report a concise chemical approach to regulate the electronic configuration for phosphorescence enhancement. After the introduction of d–pπ bonds into a phenothiazine model system, a phosphorescence lifetime enhancement of up to 19 times was observed for DOPPMO, compared to the reference PPMO. A record phosphorescence lifetime of up to 876 ms was obtained in phosphorescent phenothiazine. Theoretical calculations and single‐crystal analysis reveal that the d–pπ bond not only reduces the (n, π*) proportion of the T1 state, but also endows the rigid molecular environment with multiple intermolecular interactions, thus enabling long‐lived phosphorescence. This finding makes a valuable contribution to the prolongation of phosphorescence lifetimes and the extension of the scope of phosphorescent materials. Leuchtet länger: Die Einführung von d‐pπ‐Bindungen wurde genutzt, um die Lebensdauern organischer Phosphoreszenz zu verlängern. Das Luminogen N‐Acetylphenothiazin‐S,S‐dioxid (DOPEO) zeigt eine ultralange Lebensdauer von 876 ms mit einer Phosphoreszenz‐Quantenausbeute von 8.2 %, was die höchsten Werte von Phenothiazin‐basierten organischen Phosphoreszenz‐Leuchtstoffen sind.