Multifunctional Fluorescent Materials with Reversible Mechanochromism and Distinct Photochromism

It is extremely significant and desirable to integrate the fascinating mechanochromism and photochromism in one simple molecule. Herein, two intriguing cyanostilbene-containing triphenylamine (TPA)/tetraphenylethylene (TPE) derivatives ( Z -TPA-MB and Z -TPE-MB) are elaborately designed, which not only display excellent aggregation-induced emission (AIE) properties with high solid-state fluorescence quantum yields (60.9% and 63.8%) but also exhibit reversible and high contrast mechanochromism and distinct photochromism. The powders of Z -TPA-MB and Z -TPE-MB both exhibit large red-shift under mechanical stimulation based on the highly twisted conformation and the resulting loose packing mode, accompanied by significant changes in apparent and fluorescent colors. Meanwhile, their solid-state fluorescence can be reversibly switched between crystalline and amorphous structures through alternating grinding and solvent fuming, exhibiting good fatigue resistance. In addition, the molecules also exhibit distinct dual-mode photochromic behaviors owing to the presence of cyanostilbene moieties: under 420/365 nm light irradiation, the fluorescence of which decreases in solution owing to the photo-isomerization, while decreases and blue-shifts in the aggregated state owing to the photodimerization reactions. The reversible, tractable, and high-contrast mechanochromism and distinct photochromism of the cyanostilbene-containing molecules endow them with excellent application prospects in the field of rewritable papers and photo-patterning.