The influence of the molecular packing on the room temperature phosphorescence of purely organic luminogens

TLDR

Organic luminogens with persistent room‑temperature phosphorescence are sought after for optoelectronic devices and bioimaging, yet they remain scarce because their mechanisms and design guidelines are unclear. The study develops seven 10‑phenyl‑10H‑phenothiazine‑5,5‑dioxide derivatives to investigate their RTP properties, underlying mechanisms, and imaging potential. Seven derivatives were synthesized and characterized to uncover how molecular packing influences their RTP behavior. Strong π–π interactions in the solid state promote persistent RTP, with CS‑CF3 exhibiting photo‑induced phosphorescence that responds to packing changes and CS‑F demonstrating a long RTP lifetime suitable for real‑time excitation‑free imaging in living mice, thereby advancing both practical applications and mechanistic understanding.

Abstract

Abstract Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π–π interactions in solid state can promote the persistent RTP. Particularly, CS-CF 3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.