Colorimetric detection of oxidizing metal ions using anilide-poly(phenylacetylene)s

Poly(phenylacetylene)s (PPAs) bearing para-substituted anilide pendant groups are sensitive to the presence of oxidizing metal ions such as Cu²⁺, Hg²⁺, Fe³⁺, Au³⁺ or Ce⁴⁺ due to a redox reaction between the anilide-PPA and the metal ion. Using a library of six different PPAs containing diverse chiral pendant groups connected to the PPA backbone through the N (anilide) or C (benzamide) atoms of an amide group used as a linker, it was found that anilide-PPAs are sensitive to oxidizing metal ions. In these polymers, and through a redox reaction, a radical species is delocalized along the polyene backbone, resulting in a color change of the solution from yellow to blue. UV-Vis, ECD, IR, EPR, XPS and computational studies were carried out to demonstrate the electron transfer from PPA to the oxidizing metal once the metal coordinates with the anilide of the polymer.