Water-Soluble Sulfonate Schiff-Base Ligands as Fluorescent Detectors for Metal Ions in Drinking Water and Biological Systems

The ability to detect and selectively identify trace amounts of metal ions is of major importance for drinking water identification and biological studies. Herein, we report a series of water-soluble Schiff-base ligands capable of being fluorescent and colorimetric sensors for metal ions. Upon coordination of the metal ion to the ligand, quenching of fluorescence is observed, typically in a 1:1 ratio. The selectivity of metal ions Cu²⁺, Ni²⁺, Cr₃₊, and Co₂₊ is exhibited via fluorescence quenching accompanied by colorimetric changes, whereas that of Ag⁺ and Co²⁺ is observed through colorimetric changes alone. Additionally, pH sensing studies were performed for the potential use of these ligands in biological applications.