Crystalline solid responsive to mechanical and acidic stimuli: Boron–fluorine derivative with TICT characteristic

• A BOPIM dye bearing dimethylamino moieties was synthesized.
• The title compound BOPIM-dma shows TICT characteristic.
• BOPIM-dma exhibits mechanochromic property.
• Photophysical properties of BOPIM-dma can be reversible tuned by acid and base.

Mechanochromism is found for a novel Boron-fluorine derivative bearing dimethylamino moieties (BOPIM-dma). The title compound shows weak or no fluorescence in organic solvents due to twisted intramolecular charge transfer (TICT), which induces energy lost via non-irradiation decay. However, intense fluorescence was observed in crystalline solid, obtained by recrystallization from organic solvents. Grinding the polycrystals of BOPIM-dma into amorphous solid induces red-shift of absorption and fluorescence quenching, which could be recovered by recrystallization. Moreover, the absorption and fluorescence of the crystalline solid could also be reversibly tuned by acidic and basic vapor.

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