Fluorescence Turn-On Sensor for Cyanide Based on a Cobalt(II)-Coumarinylsalen Complex

A Co(II)-salen based fluorescent sensor (1 center dot Co) that can selectively recognize cyanide anions in 1:2 binding stoichiometry over other anions has been developed. 1 center dot Co displayed fluorescence enhancement upon the addition of cyanide owing to the interruption of photoinduced electron transfer from the coumarin fluorophore to the cobalt(II) ion. A general regression method was developed to calculate the binding constants in the 1:2 binding system, through which the 1:2 binding between 1 center dot Co and cyanide anions was estimated to be in the range of micromolar dissociation constants.