Strategies for Constructing and Organic Afterglow Tuning of Phenothiazine Fused Ring Systems

Based on the phenothiazine core, we have synthesized three pentacyclic derivatives(E-2NAP, Z-2NAP, and Ph-ANT), together with two hexacyclic derivatives (E-NAP-ANT and Z-NAP-ANT). In the pentacyclic series, the asymmetric derivative E-2NAP shows stronger afterglow emission in frozen solution(77 K) than that of the symmetric Z-2NAP. In the solid state, Ph-ANT exhibits distinct thermally responsive behavior, with an afterglow lifetime reaching a maximum of 119.68 ms at 293 K, which is primarily attributed to a thermally activated delayed fluorescence(TADF) mechanism. Above 293 K, competition emerges between the TADF pathway and non-radiative decay channels of triplet excitons, resulting in a reduction in afterglow lifetime. In summary, through rational modulation of the fused-ring number and substitution positions, this work demonstrates effective adjustment of molecular conformation, solid-state packing, and room-temperature afterglow properties, providing important insights for the molecular design of phenothiazine-based room-temperature afterglow materials.