The considerable photostability improvement of photochromic terarylene by sulfone group

Photochromic terarylene derivative 4 which has a sulfone group at the upper benzothiophene ring is readily synthesized using Suzuki coupling reaction. It exhibits good photochromic properties. Interestingly, the closed form of the compound 4 shows a good photostability as well as a thermal stability compared with its reduced analog 3, that provides a method to enhance the photostability of versatile photochromic terarylenes under UV.