Calix[4]arene-bis(dibenzocrown-6-ethers) with one proton-ionizable group

Two 1.3-alternate calix[4]arene-biscrowns with one proton-ionizable group and two dibenzocrown-6-ether units are synthesized. The compounds exhibit high Cs+ extraction efficiency and selectivity. Cs+/Na+ and Cs+/K+ selectivities for the new N-(trifluoromethylsulfonyl)carbamoyl-substituted calix[4]arene-bis(dibenzocrown-6) are found to be higher than those for an analog with no benzo group substituents in the crown ether units. (C) 2002 Elsevier Science Ltd. All rights reserved.