Chen Deng-Gao, Chen Yi, Wu Cheng-Ham, Chen Yi-An, Chen Meng-Chi, Lin Jia-An, Huang Chun-Ying, Su Jianhua, Tian He, Chou Pi-Tai
Department of Chemistry, National (Taiwan) University, Taipei, 10617, Taiwan, R.O.C.
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai, 200237, P. R. China.
Angew Chem Int Ed Engl. 2019 Sep 16;58(38):13297-13301. doi: 10.1002/anie.201906083. Epub 2019 Aug 13.
Phenothiazine derivatives based on the 10-phenyl-10H-phenothiazine (NAS) chromophore, namely 7-phenyl-7H-benzo[c]phenothiazine (NAS-1) and 12-phenyl-12H-benzo[a]phenothiazine (NAS-2), were designed and synthesized. NAS-1 and NAS-2 are constitutional isomers with different steric strains imposed on the phenothiazine core moiety. In solution, the more-strained NAS-2 possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, bent NAS-2 exhibits prominent excimer emission as well as emission mechanochromism, which is not observed in the planar-like NAS and NAS-1. This unconventional observation results from the bent core structure facilitating π-π stacking of the peripheral naphthalene moieties. Two-photon-coupled depth-dependent emission shows spectral differences between the surface and kernel of the NAS-2 crystal, and is believed to be a general phenomenon, at least in part, for materials exhibiting emission mechanochromism.
设计并合成了基于10-苯基-10H-吩噻嗪（NAS）发色团的吩噻嗪衍生物，即7-苯基-7H-苯并[c]吩噻嗪（NAS-1）和12-苯基-12H-苯并[a]吩噻嗪（NAS-2）。NAS-1和NAS-2是同分异构体，在吩噻嗪核心部分施加了不同的空间应变。在溶液中，应变较大的NAS-2具有弯曲结构，并经历光诱导结构平面化（PISP）。在晶体中，尽管没有PISP，但弯曲的NAS-2表现出显著的激基缔合物发射以及发射机械变色现象，这在类似平面的NAS和NAS-1中未观察到。这种非常规观察结果源于弯曲的核心结构促进了外围萘部分的π-π堆积。双光子耦合深度依赖发射显示了NAS-2晶体表面和内核之间的光谱差异，并且被认为至少部分是表现出发射机械变色现象的材料的普遍现象。
