Calix[4]arene Having a Convergent Carboxylic Acid Functions: Synthesis and Ion Binding Properties of a New Cs+-selective Ionophore

Calix[4]arene bearing a convergent carboxylic acid function employing the Kempʹs triacid motif exhibited a pronounced selective ionophoric behavior toward Cs over other alkali metal ions. The selectivities of calix[4]arene-acid for Cs over Rb, K, and Na ions assessed by competitive transport experiments were 7.9, 26, and 121, respectively.