1,2-Diarylbenzene as fast T-type photochromic switch†
Fast T-type photochromic molecules that isomerize only under photoirradiation are promising materials for ophthalmic lenses, real-time holography, security systems, and super-resolution fluorescence microscopy. In this study, we successfully developed a novel fast T-type photochromic molecular system, 1,2-diarylbenzene (DAB), by introducing tetrafluorobenzene to the ethene bridge unit of the typical P-type photochromic diarylethene. DAB changed from colorless to blue only when irradiated with ultraviolet light because it underwent photocyclization and fast thermal cycloreversion with a half-life of 130 ms at room temperature. The dramatic acceleration of thermal cycloreversion was due to the significant increase in the energy gap between the open- and closed-ring isomers and decrease in activation energy at the ground state. In addition, DAB could undergo fast photochromic reaction even in the solid state. Thus, introduction of a benzene ring to the ethene bridge unit would lead to the development of new functions for 6π-electron photochromic systems.