Wavelength-dependent multicolor photochromism and fluorescence switching based on an AIE-active skeleton by regulating the conjugation of the photoactive unit

Abstract

Organic photochromic materials present extraordinary value and exciting prospects in numerous photo-controlled practical applications; however, it is still a great challenge to achieve multiple-wavelength-controlled multicolor photochromism with dual-mode readout. Herein, we propose a general design strategy to achieve multicolor photochromic systems with dual-signaling color and fluorescence modes through a group of colorful photochromic compounds based on an AIE-active molecular skeleton. It is found that combining photochromic and fluorescent systems and designing the proper module composition of the functional subunits in an AIE-active molecule can regulate the molecule toward predominant photophysical emission or photochemical chromism in a controllable way, and multicolor photochromism can be accomplished using multicomponent mixtures with well-separated and individually addressable absorption bands by regulating the conjugation of the introduced photoactive units. The photo-triggered photochromism is attributed to the reversible cyclization/cycloreversion reaction, and the extended conjugation of the photoactive unit is the dominant contributor to the colorful coloration of the different chromophores, which ranges from red to blue. Variation of the conjugated structures of the photoactive unit not only endows these compounds with multiple-wavelength-triggered color control, but also enables the colored isomers to be decolored using visible light stimuli with distinct wavelengths, which allows the multiplexing optical systems to work in a more flexible and controllable way in advanced photo-controlled patterning and anti-counterfeiting applications.