A supramolecular assembly of a multifunctional calix[4]arene with alkali and alkaline earth cations in solution and in the solid state

p-tert-Butylcalix[4]arene derivatives 2 and 4 bearing one carboxy-lic acid, one ester and two phenolic groups on the lower rim form pH-dependent mononuclear or binuclear assemblies with alkali (excluding lithium) and alkaline earth cations. The structures of binuclear K+ complexes 5 and 6 of 2 and 4, respectively, have been determined by X-ray diffraction.