Synthesis, complexation, and membrane transport studies of 1,3-alternate calix(4)arene-crown-6 conformers: a new class of cesium selective ionophores

Reaction of pentaethylene glycol ditosylate with 1,3-dialkoxycalix(4)arenes produces the corresponding 1,3-alternate calix(4)arene-crown-6 conformers, which prefer Cs+ for complexation. The complexes of these conformers with Cs+ exhibit high stability constants. Preorganization of the conformers accounts for the observed entropy of complexation. X-ray studies reveal the presence of Cs+ cations between the two aromatic rings. Transportation of Cs+ cations by liquid membranes are supported by these conformers.