Sensing of toxic metal ions from aqueous media is a challenging task. Our group has previously demonstrated that o-phenylenediamine-based aryl sulfonamides chelate to Pb(II) and Cd(II), enabling efficient extraction and selective sensing. Analogous thioamide ligands can provide additional soft coordination sites, and the potential for optical detection in the visible: The bis(p-tolyl) thioamide derivative of o-phenylenediamine synthesized from the corresponding diamide was shown to be an optical extraction-based sensor for Pb(II). It was also shown to complex Cd(II) and Hg(II) by visible color changes and UV-Vis spectroscopy. The metal-thioamide complexes were synthesized under mild conditions after reaction of the ligand with a suspension of metal salts in different solvents, and were characterized spectroscopically. 1H-NMR spectroscopy suggests that this thioamide ligand presents an unusual coordination pattern for toxic metals, which is distinctly different from the previously studied sulfonamide analogs. These experiments serve as a foundation for future studies of the complexation between these ligand types and Hg(II) and for possibly developing more successful methods that will increase the efficiency of this interaction, for application in Hg(II) sensing.

Bis-thioamide ligand derived from o-phenylenediamine as an extraction-based optical sensor for toxic metals

251st National Meeting (2016)

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