Photoresponsive Host−Guest Systems Based on a New Azobenzene-Containing Crytpand

A new azobenzene-bridged cryptand was synthesized; it can be well controlled between cis and trans isomers by irradiation with different wavelengths or by being heated. It was found that this cryptand exhibits an ON−OFF binding ability with 2,7-diazapyrenium (DAP) derivatives. It binds DAP derivatives as the cis isomer only, as demonstrated by various methods. The fluorescence property of DAP derivatives endows these host−guest systems with detectable fluorescent output signals, which makes monitoring these photoresponsive systems convenient.