Novel chromatic reaction based on the redox reaction between tertiary aromatic amines and gold(Ⅲ) or cerium(Ⅳ)

Herein, a novel chromatic reaction based on the oxidative self-coupling of tertiary aromatic amines and driven by a redox reaction with gold(III) or cerium(IV) is developed. The dimers resulting from the oxidation of tertiary aromatic amines with gold(III) or cerium(IV) show colors depending on their chemical structures. Substituting a hydrogen atom on the aromatic ring with a methyl or methoxy group induces a bathochromic shift in the color developed via oxidation. This redox reaction is highly selective for gold(III) and cerium(IV) because of their high redox potentials and complexation abilities with tertiary aromatic amines, thus suggesting the development of a selective analytical method for gold(III) and cerium(IV). Cyclic voltammograms and ultraviolet–visible light absorption spectra confirm that the oxidative coupling of tertiary aromatic amines develops color. The addition of reductants, such as l-ascorbic acid, degrades the color of the resultant colored species, thus indicating that the quinoid structure of the colored species caused color development. Thus, the developed redox reaction of tertiary aromatic amines with gold(III) or cerium(IV) provides a new chromogenic platform for determining gold(III), cerium(IV), and ascorbic acid.