Toggle-switchable fluorescence of bisindolylmaleimide derivatives by reversible esterification/hydrolysis

Isomers based on the bisindolylmaleimide architecture were reported in this Letter. Introducing hydroxyl to this architecture lead to quenching the fluorescence of bisindolylmaleimide. The fluorescence was recovered with its hydroxyl group esterified. Ester group can be easily transformed to hydroxyl group by hydrolysis reaction. Thus, a toggle-switchable fluorescence, 'off-on' cycle can be established on the basis of reversible esterification/hydrolysis reaction.