Photoinduced multi-color emission of naphthalenediimide radical in different solvents and dynamic anti-counterfeiting film.

An NDI-based compound (2-NDI) with 2-butyric acid attached at imide N atoms was intelligently constructed. 2-NDI exhibits 2-NDI − monomer (low concentration) and 2-NDI − excimer (high concentration) emission state in different solvents after 365 nm illumination, forming multi-color radical fluorescence. It shows dynamic free radical emission in DMF solvent with rare white light emission. Theoretical calculations show that the fluorescence is derived from the D n -D 0 vertical emission of 2-NDI − monomer and 2-NDI − excimer. Finally, 2-NDI is made into PMMA film, which is successfully applied to information anti-counterfeiting and dynamic information encryption systems. [Display omitted] • 2-NDI was synthesized and showed different free radical emission colors in different solvents. • The dynamic fluorescence of 2-NDI in DMF solution changed with the irradiation time. • 2-NDI shows different free radical fluorescence emission types at different concentrations. • DFT shows that the free radical fluorescence is the vertical emission of D n -D 0. • 2-NDI PMMA film can be used for dynamic information encryption and anti-counterfeiting. Developing innovative materials with environmentally stable 1,4,5,8-Naphthalene diimide radicals (NDI −) emissions is significant. In this work, we have successfully constructed an NDI-based material 2-NDI (N, N′-bis(2-butyric acid)-1,4,5,8-naphthalene diimide) that emits strong fluorescence in solvents and polymethyl methacrylate (PMMA) upon irradiation. The radical 2-NDI − exhibits multi-color emission in different solvent systems, and the fluorescence emission is concentration-dependent. It is worth noting that it exhibits a rare dynamic fluorescence in DMF solvent, with the fluorescence color changing from yellow-green to orange and finally to white. Theoretical calculations show that the fluorescence is derived from the D n -D 0 vertical emission of 2-NDI − monomer and excimer. Owing to the outstanding free radical fluorescence emission properties, various films (PMMA systems) based on 2-NDI in different solvents have been successfully made to be applied in multiple dynamic information anti-counterfeiting and encryption. This work achieved simple and stable fluorescence emission based on NDI −, making it a potential candidate for practical applications and providing a new platform for the future design of NDI-based photochromic materials. [ABSTRACT FROM AUTHOR]