Azophotoswitches containing thiazole, isothiazole, thiadiazole, and isothiadiazole.

We report a novel class of azophotoswitches incorporating various five-membered heteroaryl units such as thiazole, isothiazole, thiadiazole, and isothiadiazole. These azophotoswitches were developed through an initial screening of 24 compounds using DFT calculations to identify those with the wavelength of maximum absorption (λ_max) at a long wavelength. Subsequently, eight selected azophotoswitches were synthesized. Compounds containing both thiazole and isothiazole moieties showed relatively long λ_max compared to the other synthesized compounds. These azophotoswitches exhibited reversible isomerization under visible light irradiation at 430 nm, 450 nm, 470 nm (trans to cis) and 525 nm (cis to trans). Analysis of the X-ray crystal structures of the cis isomer of phenylazo[1,3,4-thiadiazole] exhibited a unique orthogonal geometry.