A sinapic acid-calix[4]arene hybrid selectively binds Pb2+ over Hg2+ and Cd2+

The sinapic acid-calixarene hybrid 2 has a marked selectivity for Pb2+ over Hg2+ and Cd2+. Its selectivity for Pb2+ is much greater than that of the parent ''monomer” 1, owing to the cooperative effect resulting from the simultaneous presence of the sinapyl units arranged on the calix[4]-arene upper rim.