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Phenothiazine Scope: Steric Strain Induced Planarization and Excimer Formation
Author(s) -
Chen DengGao,
Chen Yi,
Wu ChengHam,
Chen YiAn,
Chen MengChi,
Lin JiaAn,
Huang ChunYing,
Su Jianhua,
Tian He,
Chou PiTai
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201906083
Subject(s) - phenothiazine , chromophore , moiety , steric effects , excimer , photochemistry , stacking , chemistry , crystal (programming language) , crystallography , materials science , stereochemistry , fluorescence , optics , organic chemistry , physics , medicine , pharmacology , computer science , programming language
Phenothiazine derivatives based on the 10‐phenyl‐10H‐phenothiazine ( NAS ) chromophore, namely 7‐phenyl‐7 H ‐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.