A Hexahomotrioxacalix[3]arene-Based Ditopic Receptor for Alkylammonium Ions Controlled by Ag(+) Ions

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups was successfully synthesized, which has a C(3)-symmetric conformation and is capable of binding alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind alkylammonium ions through the π-cavity formed by three aryl rings. This behaviour is consistent with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for endo-complexation. As a C(3)-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also bind an Ag(+) ion, and the nitrogen atoms are turned towards the inside of the cavity and interact with Ag(+). After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag(+), the original C(3)-symmetry was retained and higher complexation selectivity for n-BuNH(3)(+) versus t-BuNH(3)(+) was observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and recognition of Ag(+) and n-BuNH(3)(+) ions.