Photoresponsive Crown Ethers. 9. Cylindrical and Phane Crown Ethers with Azobenzene Segments as a Light-switch Functional Group

Abstract

Abstract Cylindrical and phane crown ethers with azobenzene segments as a light-switch functional group were synthesized. Cylindrical ionophores in which two diazacrown ethers are linked by two photoresponsive azobenzene pillars change their binding ability for polymethylenediammonium salts in response to photoirradiation. Thus, the distance between the two crown rings can be photocontrolled. A phane-type ionophore in which 1,23-bis(p-aminophenoxy)-3,6,9,12,15,18,21-heptaoxatricosane is linked by a trans-4,4′-azobenzenedicarbonyl segment exhibits no affinity with all alkali metal cations but significantly binds Rb+ and Cs+ under UV-light irradiation. This is the example of the “all-or-nothing” control of the ion-binding ability and implies that a crown-like loop emerges only when the azobenzene segment is photoisomerized to the cis-configuration. These ionophores are categorized to novel photoresponsive crown ethers.