A fluorescent sensor for Zn²⁺ and NO₂^- based on the rational control of CN isomerization

A new strategy for the ultrasensitive sensing of cations and anions based on the control of CN isomerization has been developed. Imine-derived ligand L is non-fluorescent due to the CN isomerization process, whereas its ternary complex with ZnCl₂ is moderately fluorescent because of the partial inhibition of CN isomerization. Such a ternary complex can give a remarkable fluorescence increase when it interacts with nitrite because of the much more efficient suppression of CN isomerization. This modulation process of CN isomerization can thus be used for the highly selective detection of Zn²⁺ and NO₂^- in an aqueous solution.