Naphthalimide‐Conjugated Spiropyran: Dual‐State Emission and Photo‐Responsive Dynamic Fluorescence Color for Information Encryption Application

Abstract Developing photo‐switch molecules that show fluorescence in both monomeric and aggregated states, with light‐controllable fluorescence wavelength is far‐reaching and a great challenge. Spiropyran (SP) has received considerable attention in this field. Herein, by conjugating naphthalimide to the indole moiety of SP, a new spiropyran derivative, named NMI‐SP is obtained. NMI‐SP shows dual‐state emission with excellent fluorescence in both its monomeric and aggregated states, attributed to the intramolecular charge transfer character. Moreover, NMI‐SP demonstrates obvious photochromic behavior, accompanied by the visible color change from yellow to green in THF solution, and photo‐responsive fluorescence color change from orange to red in the aggregated state. This work provides new insights into the design of photo‐responsive materials based on SP fluorophore and highlights their potential applications in digital coding and information conversion.