Is Color-Specific Photoswitching in Dual-Color Fluorescence Systems Possible? Manipulating Intermolecular Energy Transfer among Two Different Fluorophores and One Photoswitch

Color-specific photoswitching in dual-color fluorescent system is important due to its potential in bioimaging and other applications. It requires elaborate manipulation of intermolecular energy transfer (ET) among two different fluorophores and one photochromic chromophore. Here, the rationally designed color-specific photoswitching system composed of two excited-state intramolecular proton transfer fluorophores and a color-specific photoswitchable diarylethene in poly(methyl methacrylate) film is reported. Through their unique photophysical properties, this system demonstrates an entirely new principle of color-specific photoswitching, which includes the frustration of ET between two fluorophores and the selective ET from only one specific fluorophore to the photochromic switch. In this novel class of smart fluorescent film, reversible photoswitching and photopatterning are successfully demonstrated.