Photoresponsive macrocycles for selective binding and release of sulfate.

A series of new photoresponsive macrocyclic anion receptors were synthesized via integration of an azobenzene unit and multiple anion binding sites. They exhibited highly selective binding to dianionic sulfate over other tested anions and the reversible release of sulfate could be triggered by visible light as inferred from mass spectroscopy, crystallographical analysis, NMR spectroscopy, and theoretical calculations.