Cesium Selective Calix[6]arene Bisbridged Receptor

Calixcrowns are macromolecular hybrid structures com-posed of calix[n]arenes and crown ethers which have been demonstrated to be very effective complexing agents for alkali and other metal ions.1-3 In particular, calix[4]arene crown-6 hosts have been extensively investigated in the sequestration and removal of radioactive Cs137 ions from aqueous waste mixtures.4,5 Cesium-137 is a relatively abundant nuclear fission product and constitutes a major source of heat in nuclear waters6,7 along with strontium-90. Much effort has been made to the development of improved processes8,9 for the removal of cesium-137 from nuclear wastes. For the efficient removal of cesium, several crown ethers have been prepared and their binding properties were investigated. Calixcrowns have been constructed from all four conformational isomers of calix[4]arenes (cone, partia