Photoswitchable Turn-on Mode Fluorescent Diarylethenes: Strategies for Controlling the Switching Response

A new type of photoswitchable fluorescent diarylethenes, which have no fluorophore unit but emit strong fluorescence (Φf ∼ 0.9) in the closed-ring isomers, has been developed. They are sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentenes and 1,2-bis(2-alkyl-1-benzothiophen-3-yl)perfluorocyclopentenes. By chemical modifications of the structures their switching response was tuned to meet the requirements for super-resolution fluorescence microscopies. The water-soluble derivatives have been successfully applied to acquire super-resolution bioimages using a single-wavelength visible beam.