Redox-Switchable Cyan Fluorescence of a BODIPY Analog Inspired by Propentdyopent Pigments

The combination of reversible redox chemistry and bright redox-responsive emission properties is key to the development of electrofluorochromic switches for applications in bioimaging and optoelectronics. Herein, the redox-active dipyrrin-1,9-dione fragment, which is characteristic of the propentdyopent family of heme metabolites and urinary pigments, is employed for the synthesis of a BODIPY analog. This boron difluoride complex exhibits bright fluorescence in organic solvents and a significant ipsochromic shift to the cyan region when compared to typical green BODIPY dyes. Electrochemical and spectroscopic measurements show that the dipyrrindione ligand acts as an electron reservoir by hosting an unpaired spin upon one-electron reduction. This ligand-based redox event reversibly abolishes the fluorescence emission, thus switching off the novel electrofluorochromic system.