Molecular Packing‐Controlled Mechanical‐Induced Emission Enhancement of Tetraphenylethene‐Functionalised Pyrazoline Derivatives

Abstract

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.

Design of High-Contrast Mechanochromic Materials Based on Aggregation-Induced Emissive Pyran Derivatives Guided by Polymorph Predictions

“…23,24 In some cases, both the conformation and molecular packing might be changed under stimuli. [25][26][27] Therefore, questions arise regarding which kind of molecule has the potential to aggregate in both monomer (namely without intermolecular π-π interaction) and π-dimer (with strong π-π interaction between neighboring molecules) and what kind of molecule can comprise conformations with a significant difference? If we can calculate the potential polymorphs of the designed molecules, we might be able to predict their MC behavior.…”

One-Step Transformations from ACQ Luminogens to DSEgens via the Boc Protection Process

“…For the emission characteristics, the maximum fluorescence of ROIN is at 574 nm, while the compound ROIN-B exhibits a blue shift and peaks at 542 nm in the emission spectra, as shown in Figure A,B. The blue shifts of the maximum absorption (λ max , abs ) and the maximum emission (λ max , em ) from ROIN to ROIN-B might result from the decrease of the donor–acceptor (D-A) effect for ROIN-B …”

Mechanically responsive luminescent films based on copper iodide clusters

“…98,99 Spin coating of solutions or suspensions of the active compound on a substrate is also reported and its impregnation in absorbing substrates too. [100][101][102] Vapor-deposited films have been reported as well. 103 In the case of 1, its thermal decomposition and very poor solubility in common organic solvents hampers vacuum evaporation and direct deposition of a solution.…”