Thianthrene Position Isomerism in Polycyclic Aromatic Hydrocarbons toward Efficient and Long-Lived Room-Temperature Phosphorescence

Purely organic room-temperature phosphorescence (RTP) materials have garnered significant attention. However, balancing the phosphorescence quantum yield (Φ_P) and phosphorescence lifetime (τ_P) remains a fundamental challenge in developing high-performance organic RTP materials. Herein, we utilize a facile strategy of functional unit combination to enhance the RTP performance of polycyclic aromatic hydrocarbons (PAHs), such as triphenylene, phenanthrene, naphthalene, and pyrene, through site-selective functionalization at 1- or 2-positions of thianthrene (TA). Our findings reveal a rule that for the PAHs modified by 1- and 2-positioned TA, the former exhibits a longer τ_P, while the latter presents a higher Φ_P. Particularly, 2-positioned TA-modified PAHs achieve an optimal balance between higher Φ_P (up to 50.59%) and long τ_P (>100 ms), due to their appropriately improved intersystem crossing and phosphorescence radiation ability, which can be ascribed to an allowed charge transfer between the PAH and the 2-positioned TA. Furthermore, employing the characters of high Φ_P and long τ_P obtained in these compounds, we explore their application potential in dynamically photoresponsive tags and time-dependent anticounterfeiting. Consequently, this work can provide a generalizable strategy at the molecular level for achieving a high-performance RTP in purely organic materials.