A bis-calix[4]arene-supported [CuII16] cage.

Reaction of 2,2'-bis--Bu-calix[4]arene (HL) with Cu(NO)·3HO and -methyldiethanolamine (Me-deaH) in a basic dmf/MeOH mixture affords [CuII16(L)(Me-dea)(μ-NO)(μ-OH)(dmf)(MeOH)(HO)](HL)·16dmf·4HO (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu], in which the four capping metal ions are the Cu ions housed in the calix[4]arene polyphenolic pockets. The [CuII8] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the -methyldiethanolamine co-ligands forming dimeric [CuII2] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated HL ligand per [Cu] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an = 1 ground state, while EPR is consistent with a large zero-field splitting.