A new "switched-on" crown ether which exhibits a reversible all-or-none ion-binding ability

Abstract A new photoresponsive crown ether (2) in which the poly)oxyethylene) chain is linked to 4− and 4′-position of azobenzene was synthesized. Trans-(2) completely lacked the affinity to alkali metal cations, while photoisomerized cis-(2) was capable of binding K + , Rb + , and Cs + .