Synthesis of a Tetrahomodioxacalix[4]arene Tetraamide and the Crystal Structure of Its Lead Ion Complex

The 1,4-alternate tetrahomodioxacalix[4]arene tetraamide 4 with four p-phenyl groups on its upper rim was synthesized. In two-phase metal picrate extraction, 4 exhibited Pb2+ selectivity with formation of a 1:1 complex in chloroform. In the solid-state structure of the 4·Pb(Pic)2 complex, Pb2+ is bound by the carbonyl oxygens of two adjacent amide groups and an aryl−alkyl ether oxygen atom of one of these amide-containing substituents. The crystal structure and 1H NMR spectrum of the 4·Pb2+ complex reveals π-metal ion complexation of one aromatic ring in the ligand with Pb2+.