No abstract

, which are triply, doubly or singly protonated, respectively. The superanions possess a central sodium ion bound by a crown ether and two trans water molecules; this moiety is further shrouded by two calixarenes. The di-and trinuclear cations can be leached from the solid complexes by treatment with aqueous HClO 4 , and the complex containing the tetranuclear species is selectively formed from a solution containing a mixture of the various polynuclear cations.

Crystals of composition, where x ϩ z = 7 and L = p-sulfonatocalix[4]arene, were obtained from an aqueous solution containing monomeric and oligomeric aluminium species, Na 4 L and 18-crown-6. The crystal structure features three distinct elements: the cationic Keggin ion [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7ϩ , an anionic capsule [Na(18-crown-6)(H 2 O) 2 L 2 (H ϩ ) w ] xϪ and a water bearing calixarene. The anionic capsule comprises a central sodium ion bound by 18-crown-6 and two trans water molecules, which is in turn encapsulated by two p-sulfonatocalix [4]arene molecules in a head-to-head arrangement. The different components are held together in the solid state by an intricate pattern of hydrogen bonds, complemented by other supramolecular interactions such as π-π stacking.