Reversible switching of a fluorescent host-guest system: Cryptand interchange between two different recognition sites by regulating on guest molecule

Novel acid/base-controllable fluorescent host-guest system among 1, 2 and 3 was successfully constructed, in which cryptand host 1 could reversibly interchange between two different recognition sites 2 and 3 by regulating on guest molecule 3, as evidenced by 1H NMR and fluorescence spectroscopy.207