Potassium Selective Calix[4]semitubes

A new class of ionophore consisting of two calix[4]arene units linked through the lower rim by two ethylene chains, in combination with propyl ether and phenolic functional groups, has been developed. These calix[4]semitube molecules exhibit remarkable selectivity and fast complexation kinetics for potassium over all Group 1 metal cations. Molecular modelling studies, using structural models derived from crystallographic data, suggest the potassium cation is complexed by a horizontal, side‐on route and not through the calix[4]arene annulus. The length of the bridging alkylene chain between the respective calix[4]arenes of the semitube structure dictates the strength and selectivity of alkali metal cation binding. A new class of ionophore consisting of two calix[4]arene units linked by two ethylene chains at the lower rim, together with propyl ether groups, exhibits remarkable selectivity for potassium over all Group 1 metal cations (see picture). The length of the bridging alkylene chain between the respective calix[4]arene moieties of the calixsemitube structure critically dictates the selectivity and strength of alkali metal cation binding.