Phenothiazine Scope: Steric Strain Induced Planarization and Excimer Formation. (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. Volume 131:Number 38(2019)
• Page Start: 13431
• Page End: 13435
• Publication Date: 2019-08-13
• Subjects: Excimere -- Heterocyclen -- Konformationsanalyse -- Ladungstransfer -- Sterische Hinderung; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201906083
• Languages: English
• ISSNs: 0044-8249

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 : Phenothiazinderivate wurden gezielt entworfen und synthetisiert. In Lösung weist die stärker gespannte Struktur (siehe Schema) eine gebogene Struktur auf und unterliegt einer photoinduzierten Strukturplanarisierung (PISP). Im Kristall zeigt die Verbindung trotz des Fehlens von PISP sowohl eine ausgeprägte Excimer‐Emission als auch Mechanochromie.