Aza-crown-ether-appended xanthene: Selective ratiometric fluorescent probe for silver(I) ion based on arene-metal ion interaction

In this Communication, we report on the development of a ratiometric fluorescent probe for silver(I) ions (Ag^I) based on an arene-metal ion interaction. The probe selectively senses Ag^I among various metal ions with a large-emission red shift under aqueous conditions, enabling the selective ratiometric detection of Ag^I. X-ray crystallography and NMR analyses reveal that Ag^I comes into close contact with the fluorophore, which induces a large-emission red shift. The high sensing selectivity of the probe toward Ag^I might be attributable to the restricted rigid conformation of the cyclic aza crown ether, which exclusively binds Ag^I. In addition to Ag^I sensing, the Ag^I complex of the probe is also used for the ratiometric sensing of a cyanide anion (CN^-), highlighting the utility of the reported probe in fluorescence sensing.