Spontaneous Decarboxylation of Ferrocenecarboxylate using 1,4-Benzoquinone as Oxidant: Application to the Chemical Grafting of Glassy Carbon Surfaces

The covalent modification of glassy carbon electrode with ferrocenyl moieties was performed in acetonitrile using a mixture of ferrocenecarboxylate (FcCOO(-)) and ferrocenecarboxylic acid (FcCOOH). This process is activated by 1,4-benzoquinone (Q), which plays the role of oxidant. The carboxylate induces the redox reduction of the quinone whereas an excess of the carboxylic acid drives the protonation of the reduced quinone to yield hydroquinone (QH(2)) as a reaction product. Due to the homogeneous oxidation of the carboxylate derivative, carbon dioxide and ferrocenyl radicals (Fc(center dot)) are released, such as occurs in the classical Kolbe reaction. The generation of ferrocenyl radicals allows the chemical derivatization of non-connected glassy carbon surfaces. The homogeneous redox reaction between the 1,4-benzoquinone and ferrocenecarboxylate proceeded slowly and permitted the covalent attachment of a thin film with ferrocenyl moieties, whose presence on the carbon surface was evidenced from cyclic voltammetry and atomic force microscopy (AFM) measurements.