Oxygen-responsive high-efficiency orange-red room-temperature phosphorescence from chalcogen-containing dibenzo[a,c]phenazine foldamers.

Efficient orange-red/red room-temperature phosphorescence (RTP) in purely organic materials is highly desirable for bio-imaging and information security but remains scarce due to the energy gap law and the challenge in achieving strong spin-orbit coupling (SOC) in red-emitting systems. Herein, a functional unit combination strategy was employed to develop a series of orange-red-emitting RTP materials. By modifying a dibenzo[a,c]phenazine (DBP) emissive core with flexible chalcogen-containing foldamers (phenylselenyl, phenylthio, or phenoxyl), three new compounds (O-DBP, S-DBP, and Se-DBP) were synthesized. While the DBP core governs the triplet energy level and emission color, the varied chalcogen-containing foldamers significantly modulate the phosphorescence efficiency. Notably, Se-DBP achieves orange-red RTP peaking at 630 nm with a phosphorescence quantum yield of 33.04% in doped PMMA films. Our findings reveal that the superior performance of Se-DBP originates from enhanced SOC driven by the synergy between the heavy-atom effect and n/π orbital decoupling mechanism in the phenylselenyl-containing foldamer. Furthermore, these materials exhibit unique oxygen-sensitive RTP properties, which enable potential applications in anti-counterfeiting and encryption, ratiometric oxygen sensing, and cellular hypoxia imaging. This work not only validates the effectiveness of the functional unit combination strategy for developing high-efficiency orange-red/red RTP materials, but also expands their applicability across diverse fields.