Rational design of cesium-selective ionophores: Dihydrocalix[4]arene crown-6 ethers

Molecular mechanics calculations performed on calix[4]arene crown-6 ethers predict that the 1,3-dihydro derivatives will exhibit greater complementarity for potassium and cesium ions than the parent 1,3-bis(alkyloxy) calixcrowns. The X-ray crystal structures of 1,3-alt-bis(octyloxy)calix[4]arene benzocrown-6 ether, dihydrocalix[4]arene benzocrown-6 ether, and the cesium nitrate complex of dihydrocalix[4]-arene benzocrown-6 ether were determined. The structure of the cesium complex corresponds closely to the structure predicted by molecular mechanics. The dihydrocalix[4]arene crown-6 ethers exhibit enhanced cesium selectivity in the extraction of alkali-metal salts. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.