Computational design of photoswitchable anion receptors: Red-shifted and bistable di-ortho-fluoro di-ortho-chloro azobenzene derivatives

Highlights: • Three photoswitchable anion receptors were designed based on dfdc-AB. • The designed dfdc-AB-OCH₃ molecule has bistability and high E → Z conversion ratio. • dfdc-AB-OCH₃ has apparent photoswitchable selectivity for acetate anion. Photo-therapeutic applications require efficient photo-switchable anion receptor materials with high photoisomerization ratio, thermal stabilities, and anion binding affinities. Based on di-ortho-fluoro di-ortho-chloro azobenzene (dfdc-AB), a recently proposed photoswitch whose E → Z isomerization can be triggered using irradiations in the bio-optical window, we designed a series of photoswitchable anion receptors with first-principles calculations. We demonstrated that, by modifying the 3- and 5-site of the azobenzene backbone of dfdc-AB using methoxyamide groups, the resulted dfdc-AB-OCH₃ has nearly bistability, high E → Z conversion in the visible region, and apparent difference in binding affinities for $C{H}_{3}C{O}_2^{-}$ at different isomers, indicating a promising photoswitchable anion receptor in photopharmacology.