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Molecular Packing‐Controlled Mechanical‐Induced Emission Enhancement of Tetraphenylethene‐Functionalised Pyrazoline Derivatives
Author(s) -
Guo Shengmei,
Zhang Gaobin,
Kong Lin,
Tian Yupeng,
Yang Jiaxiang
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201905256
Subject(s) - fluorescence , chemical mechanical planarization , substituent , intermolecular force , photochemistry , stacking , pyrazoline , chemistry , materials science , nanotechnology , stereochemistry , organic chemistry , molecule , physics , layer (electronics) , quantum mechanics
Organic mechanofluorochromic (MFC) materials with mechanical‐induced emission enhancement (MIEE) are scarce. Herein, Aggregation‐induced emission (AIE)‐active tetraphenylethene‐functionalised pyrazoline derivatives with various non‐conjugated substituent groups (Br, F, N , N ‐dimethylamino and cyano groups for TPEB, TPEF, TPEN and TPECN, respectively) were designed and synthesised. The fluorescence spectra of the compounds in the solid state were sensitive to mechanical stimuli and exhibited unique MFC properties. The solid fluorescence peaks of all compounds were red shifted, whereas the quantum yields of TPEB, TPEF and TPEN were increased and that of TPECN was slightly reduced after grinding. The MIEE mechanism was systematically investigated through structure–property relationship studies. The results showed that the pyrazoline ring of TPEB with MIEE property formed H‐dimer aggregates with weak π–π stacking in the solid state. After grinding, the synergistic effects of conformational planarization and destructive π–π interactions induced the red shift of the fluorescence peak and the intensity enhanced. TPECN formed incompact J‐aggregates with weak intermolecular interactions instead. The conformational planarization and increased intermolecular interactions induced by grinding led to the red‐shifted peak and the slightly reduced intensity. These results clearly demonstrated that the translation of packing arrangements is an efficient method to design MIEE materials, which opens a new scope for designing unique MFC materials.