Extraction mechanism of lead ion with p-allylcalix[4]arene tetracarboxylic acid

25,26,27,28-Tetrakis(carboxymethoxy)-5,11,17,23-tetraallylcalix[4]arene in a cone conformation has been synthesized for the selective extraction of divalent lead ions. The extraction of divalent metal ions, such as lead, copper, nickel and zinc with p-allycalix[4]arene tetracarboxylic acid was investigated. The extraction data and chemical shift of 1H-NMR for the extractant, caused by the complexation with lead, supports the conclusion that two lead ions are extracted stepwise. The complex structure was proposed.