AIE activity, mechanochromism, acidchromism, and high-level anti-counterfeiting based on multifunctional tetraphenylvinyl imidazolopyridine

TPE-IP was designed and synthesized by assembling tetraphenylethene (TPE) and imidazopyridine (IP) units, with weak push- pull molecular structure and propeller-like conformation, which were confirmed by fluorescence emission in various solvents and theoretical calculations. TPE-IP showed aggregation-induced enhanced emission (AIEE) activity due to the suppressed molecular motions in aggregated states. Interestingly, TPE-IP exhibited dual-band fluorescence emission in various solvents, deriving from localized and intramolecular charge transfer states. By grinding and heating, TPE-IP presented reversible mechanochromism, accompanied by a transition between deep blue and green fluorescence. Moreover, TPE-IP displayed high-contrast acidchromism, but with different responses to HCl, CF3COOH, and CH3COOH fuming. Meanwhile, the reversibile acidchromism could be completed by HCl/CH3COOH and Et3N fuming, but not for CF3COOH and Et3N fuming. At last but not least, TPE-IP has the potential to be applied in the fields of anti-counterfeiting and information encryption.