A 4-state acid-base controlled molecular switch based on a host-guest system

A novel Zn^II funnel complex that presents three phenol functions within a calix[6]arene macrocycle is described. Host-guest studies, monitored by ¹H NMR spectroscopy, evaluate the impact of the replacement of three anisole moieties present in a previously described system with phenols. It is now shown that the dicationic complex is responsive to anions, whereas deprotonation of one phenol unit completely inhibits any hosting response. These properties, combined with those of the corresponding protonated ligand, allow us to obtain different molecular switches, and one of them shows guest embedment changes between four different host states, thus giving rise to a rare case of a triple molecular switch.