A Spiropyran-AIEgen (aggregation-induced emission luminogen) complex molecule was designed, synthesized and characterized. After attaching spiropyran (SP) moiety on tetraphenylethylene (TPE, an iconic AIEgen), the new material showed multi-color changing property with its fluorescence covering the entire visible region under different external mechanical stimuli. Under grinding, the covalent bonding between SP and TPE enabled the tuning of the fluorescence from no color change, two-color switch to three-color switch due to the amorphization of TPE moiety and the isomerization of spiropyran moiety. Under different controlled hydrostatic pressures, the fluorescence spectra showed a continuous and significant red shift of the peak from blue, via cyan and green, to yellow. The <i>in-situ</i> multi-color switching was realized based on distinct pressure threshold of the conformational planarization/intermolecular interaction changes and the isomerization of spiropyran. The covalently bonded spiropyran moiety helped to enhance the response of the TPE AIEgen under pressure to show more remarkable color changes. The molecular design was shown to be successful in tuning the mechanochromic responses of a new material induced by grinding or high pressures. The excellent mechanochromic properties, such as multi-color changes, great responses in a wider visible region and the enhanced fluorescence intensity, make this material a great candidate for sensor materials such as pressure sensors, security inks (banknotes, identity documents, etc.), mechanoprobes, etc.

Molecular design, synthesis and characterization of a spiropyran-AIEgen multi-color changing material for sensors

256th National Meeting (2018)

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