The influence of π-π stacking on the room temperature phosphorescence of phenothiazine 5,5-dioxide derivatives

The control of molecular packing in the aggregated state at the molecular design stage is significant but challenging. Herein, a strategy is provided to regulate the molecular packing as well as corresponding room temperature phosphorescence (RTP) performance. By changing the substituent, we designed five phenothiazine 5,5-dioxide derivatives to reveal their different RTP properties and inherent mechanism. Through careful analyses of experimental results, coupled with theoretical calculations, it is found that efficient intermolecular pi-pi interaction favors the long phosphorescence lifetime. Furthermore, polymorphisms with distinct intermolecular pi-pi interactions and RTP effects were obtained for compound PTZO-Cl, once again certifying the key role of strong pi-pi stacking in the persistent RTP effect. Also, these compounds with different RTP lifetimes were successfully utilized in silk-screen printing and multiple anti-counterfeiting.