Calix[4]semitube diquinone: a potassium selective redox-active ionophore

Oxidation of calix[4]semitube with Tl(OCOCF3)3 in TFA (trifluoroacetic acid) affords the novel redox-active ionophore calix[4]semitube diquinone. This receptor displays a remarkable selectivity preference for potassium cations over all other Group 1 metal cations, a property mirroring that of the parent calix[4]semitube, however its kinetics of complexation are relatively slow. The receptor exhibits substantial electrochemical recognition effects towards sodium and potassium cations.