Strontium Complexes of calixarenes amides in the solid state: structural dependence on the ligand size and on the counter ion

For the first time, crystal structures of three strontium complexes of calixarene amides have been determined. A p-tert-butylcalix[6]arene hexaamide forms a 1 : 1 complex with Sr(Pic)(2) (Pic = picrate), whereas p-tert-butylcalix[8]arene and p-methoxycalix[8]arene octaamides encapsulate two strontium cations each. The binding geometries of the metal cations depend on the ligand size and on the counter anion used (chloride or picrate).