Piezochromic luminescence of AIE-active molecular co-crystals: tunable multiple hydrogen bonding and molecular packing - 闫东鹏老师课题组

Prominent piezochromic materials play a vital role in the development of damage detection device and smart sensors. However, compared with other external stimulus (such as light, pH and temperature), understanding on intermolecular interactions and piezochromic properties based on multicomponent molecular hybrid materials is still limited and examples are quite rare. Herein, we choose 4-bis(1-cyano-2-phenyl-ethenyl)benzene (DCSB , A) as the core chromophore to self-assemble with two small organic molecules (Tetrafluorohydroquinone (B) and 2,3,5,6-Tetrafluoro-4-hydroxy-benzoic (C)), for the sake of studying their relationship between solid-state molecular arrangement and piezochromic luminescence. The as-prepared samples (two new co-crystals: A-5B and A-2C) present tunable multiple hydrogen bonds, molecular packing, and photophysical properties (such as PL colors, lifetimes, PLQYs and aggregation-induced-emissive (AIE) properties) compared with the pristine DCSB. Moreover, these two co-crystals exhibit prominent piezochromic properties and fluorescence quenching phenomena towards specific environmental stimuli (applying pressure and vapors fumigation), due to the collapse of inner supramolecular architectures. Furthermore, the mechanism on visible piezochromic behavior has been confirmed by in-situ IR micro-spectroscopy. Therefore, this work not only illustrates the relationship between the molecular configuration/packing and photophysical properties of new AIE-based co-crystals, but also develops potential applications in multiple optical sensors towards pressure and detrimental vapor (NH3).