Brannan Alexander C, Phuoc Nguyen Le, Linnolahti Mikko, Romanov Alexander S
Department of Chemistry, The University of Manchester, Manchester, United Kingdom.
Department of Chemistry, University of Eastern Finland, Joensuu, Finland.
Front Chem. 2023 Jan 6;10:1008658. doi: 10.3389/fchem.2022.1008658. eCollection 2022.
The molecular design of metal-free organic phosphors is essential for realizing persistent room-temperature phosphorescence (pRTP) despite its spin-forbidden nature. A series of halobenzonitrile-carbazoles has been prepared following a one-pot nucleophilic substitution protocol involving commercially available and laboratory-synthesized carbazoles. We demonstrate how halo- and cyano-substituents affect the molecular geometry in the crystal lattice, resulting in tilt and/or twist of the carbazole with respect to the phenyl moiety. Compounds obtained from the commercially available carbazole result in efficient pRTP of organic phosphors with a high quantum yield of up to 22% and a long excited state lifetime of up to 0.22 s. Compounds obtained from the laboratory-synthesized carbazole exhibit thermally activated delayed fluorescence with an excited state lifetime in the millisecond range. In-depth photophysical studies reveal that luminescence originates from the mixed locally excited state (LE, nπ*)/charge transfer state.
尽管无金属有机磷光体的自旋禁阻性质，但实现室温持久磷光（pRTP）的分子设计至关重要。通过一锅法亲核取代方案，使用市售和实验室合成的咔唑制备了一系列卤代苯腈 - 咔唑。我们展示了卤素和氰基取代基如何影响晶格中的分子几何结构，导致咔唑相对于苯基部分发生倾斜和/或扭曲。从市售咔唑获得的化合物可实现有机磷光体的高效pRTP，量子产率高达22%，激发态寿命长达0.22秒。从实验室合成的咔唑获得的化合物表现出热激活延迟荧光，激发态寿命在毫秒范围内。深入的光物理研究表明，发光源自混合的局域激发态（LE，nπ*）/电荷转移态。
