A combinatorial approach to discover new chelators for optical metal ion sensing

This paper reports the synthesis and characterization of metal-binding indicators with diverse optical responses on exposure to various heavy metal ions. A combinatorial approach, based on azo coupling of diazonium salts with either phenolic compounds or aromatic amines, generated a library of azo dyes. Each reaction mixture, containing the product(s) of azo coupling, was incubated with a series of solutions, each containing a different heavy metal ion. The absorbance and, in some cases, fluorescence spectra of the resulting complexes were recorded. The metal chelates showed extensive diversity in their UV-visible absorbance spectra upon binding to selected metal ions. Of the azo dyes prepared, the terdentate dyes were particularly useful, providing distinct spectral responses to three or more metal ions in a panel of seven.