Photoresponsive Crown Ethers. Part 11. Azobenzene‐Pillared Cylindrical Macrocycle As a Photoresponsive Receptor

A cylindrical ionophore (1) in which two diaza‐crown ethers are linked by two azobenzene pillars serves as a photoresponsive host molecule. In alkaline solution containing K⁺, (1) forms a cascade complex with dianionic guest molecules, but photoirradiated (1) which has a shortened cylinder cannot bind the guest molecules so effectively as (1). (1) solubilised in acidic aqueous solution by protonation of four tertiary nitrogens provides a hydrophobic cavity to bind several anionic azo dyes. The association is also suppressed by photoirradiation. The results indicate that parallel array of the azobenzene segments in (1) provides a host cavity and the photoinduced structural change is readily reflected by the association tendency. This is the first example for the photoresponsive inclusion complex.