pH-Triggered, Time-Programmable Fluorescence within an Assembly-Free Single-Molecule System

Dynamic stimulus-responsive materials (DSRMs) exhibiting time-resolved optical changes are attracting significant attention, owing to their potential applications in advanced information security technologies. Herein, we describe a design strategy for constructing DSRMs that operate within a single-molecule scaffold. These DSRMs are based on the pH-triggered, kinetically controlled conversion of leuco-triarylmethanes into rhodols via a spirocyclic ring-opening reaction, which exhibits distinct time-resolved spectral evolution in both fluorescence intensity and absorbance. We further demonstrate that the response time scale can be precisely tuned by modulating the electron-donating properties of the amino substituents. Moreover, we developed a pH-responsive, fluorescence-based information encryption system that exploits these time-resolved optical changes. Our findings provide a new perspective on the development of time-resolved dynamic materials for information encryption, storage, and display applications.