Photoinduced Fluorescence Switching in Molecular Aggregates by Topological [2+2] Cycloaddition
Guocui Pan, Zhiyuan Wu, Zhaoyang Liu, Bin Xu, Wenjing Tian
Abstract
Abstract The optical modulation of fluorescence characteristics in molecular aggregates, which mainly involves diverse molecular stacking and the consequent intermolecular interactions, remains a significant challenge for potential applications in optical anticounterfeiting, data storage, and imaging. Here we successfully realize in situ fluorescence switching in molecular aggregates of thianaphthene‐dioxide derivatives by topological [2+2] photocycloaddition, which represents a promising way to regulate the molecular stacking and alter photophysical processes. Notably, 2‐(3,5‐bis‐trifluoromethylphenyl)benzo[b]thiophene‐dioxide (BTO‐TF) in both crystal and powder forms exhibits a unique switching from an initial nonfluorescent state to a highly fluorescent state ( Φ PL =0.46) upon UV irradiation, because of the destruction of the [2+2] cycloaddition process by volume expansion of the photodimer. Furthermore, we demonstrate such a [2+2] photocycloaddition can occur when 2‐(4‐carboxypheny)benzo[b]thiophene‐dioxide (BTO‐OH) is doped within selective polymer matrixes, and can be utilized for the visualization of macrophase separation in polymer blends.