Anion-ligand coordination has been used to generate a number of supramolecular structures. Of particular interest is the transformation between different types of complexes using various stimuli. While there are multiple examples where this has been achieved with metal-ligand coordination complexes through incorporation of molecular photoswitches, the same has not yet been realized with anion-ligand coordination-driven assemblies. In this study, a sulfate-binding bis(cyclopeptide) with a photoswitchable stiff-stilbene linker is presented. Its (E)- and (Z)-isomer, and the different degree of protonation of the anion (HSO4– vs. SO42–), give rise to different assembly states. The accessible products have 1:1, 1:2 and 2:2 host-guest stoichiometries and can be interconverted by light irradiation and acid/base addition, resulting in a highly controllable responsive system that demonstrates the potential of sulfate coordination-driven supramolecular assembly.
