Phenothiazine Scope: Steric Strain Induced Planarization and Excimer Formation. Issue 38 (13th August 2019)

• Record Type: Journal Article
• Authors: 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
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 38(2019)
• Page Start: 13297
• Page End: 13301
• Publication Date: 2019-08-13
• Subjects: charge transfer -- conformation analysis -- excimers -- heterocycles -- steric hindrance; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201906083
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: 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. Abstract : In ′plane′ view : Phenothiazine derivatives were designed and synthesized. In solution, the more‐strained structure (see image) possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, it exhibits prominent excimer emission as well as emission mechanochromism.