Modification on Glassy Carbon Surfaces By Homogeneous Oxidation of Ferrocenecarboxilate in Presence of Ferrocenecarboxylic Acid and 1,4-Benzoquinone As Mediator

Abstract

The quinone-hydroquinone system is one of the most important and well studied examples of organic redox couple. This system participates as electron and proton carrier in different mechanisms involved in some biological systems. In aqueous as well as in organic solvents, the quinone molecules can be reduced following a 2-electron exchange and due to their high basicity, protonation to yield the respective hydroquinone represent a significant thermodynamic driving force. On the other hand, the oxidation of carboxylates give rise to a transient acyloxy radical whose cleavage afford CO2 and a free radical that can dimerize. This process is also highly favoured from the kinetic and thermodynamic point of view. Therefore, the combination of quinones, carboxylates and the respective carboxylic acid, would be an interesting mixture to promote the spontaneous decarboxylation and hydroquinone formation. This proposal was confirmed in this work through the study of the interaction between 1,4-benzoquinone, ferrocenecarboxylic acid and ferocenecarboxylate in acetonitrile, mainly to promote the formation of an excess of free radicals that modify chemically glassy carbon electrodes with ferrocene groups. The study was performed using cyclic voltammetry, chronoamperometry, 1H-NMR and atomic force microscopy. Figure 1