Crystal-State Quad-Mode Triplet Emissions Of D-A-A '-Aiee And Visible-Light-Excited Persistent Phosphorescence

Herein, we succeed in finding crystal-state quad-mode triplet emissions through the concept of integration of thermally activated exciton release from T-1* and introducing intramolecular electron coupling. Two new D-A-A'D type carbazol-nicotinamide isomers (P1 and P2) with the pyridine ring as the core are synthesized. The crowded D-A-A'-D structure makes P1 and P2 in a highly twisted state, which is conducive to lowering the Delta E-ST and E-TD. Excitingly, P1 and P2 achieve the crystal-state quad-mode triplet emissions, including ultralong room temperature phosphorescence from T-1*, TADP from T-1 via thermally activated exciton release (TAER), the original molecular phosphorescence from T-1 and TADF from S-1 via TAER and reverse intersystem crossing (RISC). Especially, the long-lived emissions of P1 have a rather high quantum yield of 34.3%. The intramolecular electron coupling is observed in the single crystal, verifying the original T-1 phosphorescence. The Delta E-ST and E-TD of the crystals can be calculated experimentally to be 0.19/0.18 eV and 0.19/0.20 eV, respectively, for P1 and P2. And the TAER and RISC process is validated by temperature-dependent experiment. Besides, the P2 crystals manifest fascianting visible-light-excited persistent phosphorescence and P1 shows remarkable AIEE property. To the best of our knowledge, it is the first time to find crystal-state quad-mode triplet emissions at mom temperature experimentally. This study is a breakthrough in the development of multi-mode phosphorescence mechanism.