A Tetraphenylethene-Naphthyridine-Based AIEgen TPEN with Dual Mechanochromic and Chemosensing Properties

Synthesis of new tetraphenylethene (TPE) conjugates via an innocuous route led to the revelation of a unique TPE-based aggregation-induced emissive fluorogen 3 (TPEN), which showed an interesting mechanochromic property when the emission was changed from blue to green upon grinding and green to blue upon fuming. The mechanochromic property of TPEN has been explored to prepare ink-free rewritable paper for security documentation. A detailed photophysical investigation of the TPE-naphthyridine scaffold led to the discovery of its high sensitivity to silver ions (Ag⁺) over other metal ions with a detection limit of 0.25 μM in an aqueous system. The stoichiometry of the complex of TPEN and silver ion was established to be 2:1 (TPEN:Ag⁺) on the basis of photophysical studies, mass analysis, and high-resolution mass spectrometry analysis.