Multi-State Regulation of the Dihydrogen Phosphate Binding Affinity to a Light- and Heat-Responsive Bis-Urea Receptor

A responsive bis-urea receptor can be switched between three isomers using light and heat as evidenced by ¹H NMR and UV–vis spectroscopy. Anion binding experiments (¹H NMR titrations, ESI-MS) reveal a high selectivity for dihydrogen phosphate. Importantly, a large difference in binding affinity to the interchangeable isomers is observed, which is further rationalized by DFT calculations. As a consequence, the amount of bound substrate can be controlled via photo- and thermal isomerization in a three-step process.