Facile Synthesis of Tetraphenylethene (TPE)‐Based Fluorophores Derived by π‐Extended Systems: Opposite Mechanofluorochromism, Anti‐Counterfeiting and Bioimaging

Abstract

AbstractAlthough remarkable progresses are achieved in the design and development of the mono‐shift in photoluminescence for mechanofluorochromic materials, it is still a severe challenge to explore the opposite mechanofluorochromic materials with both blue‐ and red‐shifted photoluminescence. Herein, two unprecedented 4,5‐bis(TPE)‐1H‐imidazole fused pyridine or quinoline‐based fluorophores X‐1 and X‐2 were designed and synthesized, and X‐1 and X‐2, exhibit completely opposite mechanofluorochromic behavior. Under UV lamp, the color of pristine X‐1 changed from blue to green with reversible redshifted 27 nm in fluorescence emission spectra after ground, while the color of pristine X‐2 changed from red to yellow with reversible blue‐shifted 74 nm after ground. The detailed characterizations (including PXRD, SEM and DSC) confirmed that this opposite mechanofluorochromism was attributed to the transformation of order‐crystalline and amorphous states. The crystal structure analysis and theoretical calculation further explain that opposite mechanofluorochromic behavior take into account different π–π stacking mode by induced π‐extended systems. In addition, these TPE‐based fluorophores (X‐1 and X‐2) exhibited excellent bio‐compatibility and fluorescence properties for bio‐imaging, writable data storage and anti‐counterfeiting materials.