Aqueous azobenzene switching

Photoswitches Photoswitching molecules can enable targeted delivery of drugs in the body, but the body is best penetrated by near-infrared radiation (wavelengths between 700 and 900 nanometers). Most photoswitching processes in molecules require shorter wavelengths, and high light intensities are needed to trigger two-photon processes. Dong et al. extensively substituted azobenzene molecules so that they were soluble in water and could photoswitch from the trans isomer after single-photon irradiation at 720 nanometers. The half-life of the resulting cis isomer was 1 second. The benzene rings were substituted with methoxy and pyrrolidine groups, as well as a fused dioxane ring, so that the molecule remained protonated at physiological pH while exhibiting good stability in water. J. Am. Chem. Soc. 10.1021/jacs.7b06471 (2017).