A ratiometric fluorescent chemosensor, 1,10-phenanthroline-4,7-dione, for anions in aqueous-organic media

A new fluorescent chemosensor, 1,10-phenanthroline-4,7-dione (1), which is capable of the ratiometric sensing of anions in aqueous MeCN, was developed. Chemosensor 1 recognized an anion via two NH groups in the molecule, and showed a much higher affinity for F⁻ than that of 4-quinolone, which binds to an anion at one NH group of the molecule. Upon binding to F⁻, the intensity of the emission band ascribed to the complex of 1-F⁻ was drastically enhanced, while the emission intensity of unbound 1 gradually decreased. The changes in these two emission bands enabled the successful ratiometric sensing.