Peri-Anthracenethioindigo: a Scaffold for Efficient All-Red-Light and NIR Molecular Photoswitching

Photoswitching with red light is a greatly desired capability to evade photodamage and achieve specific photoresponses. In virtually all cases however, only one switching direction uses red light while for the reverse switching UV or visible light is needed. All-red-light photoswitching brings with it the obvious advantage of pushing photoswitching to the limit of the low-energy spectrum but no viable system is available currently. In this work we report on peri-anthracenethioindigo (PAT) as molecular scaffold for highly efficient all-red-light photoswitching with outstanding performance and property profile. The PAT photoswitch provides NIR absorption up to 850 nm, large negative photochromism with more than 140 nm maxima shifts and changes color from green to blue upon irradiation with two shades of red light. Thermal stability of the metastable Z isomer is high with a corresponding half-life of several days at 20 °C. Application for red-light responsive polymers undergoing pronounced and reversible green to blue color changes is demonstrated evidencing spatially resolved photoswitching. The PAT photoswitch thus offers unique responsiveness to very low energy light together with predictable and large geometrical changes within a rigid molecular scaffold. We expect a plethora of applications for PAT in the near future in all chemistry-related areas.