Electrochemical Behavior of Quinones Classically Used for Bioenergetical Applications: Considerations and Insights about the Anodic Side

Quinones are electrochemical probes which are used for a large range of applications including bioenergetics. One electrochemical feature of quinones is their possible slow electron transfer kinetics. In this article we compared several quinones towards electron transfer kinetics and the ability of anodic pretreatment to increase electron transfer rate constant. Rotating disk electrode and chronoamperometry measurements were used to revisit their electrochemical behavior. Additionally, the number of electrons exchanged as a function of the characteristic time was used as a proxy to investigate kinetic limitations. A model was suggested to rationalize our results. Beyond a classification of quinones regarding the kinetic and thermodynamic ability of the hydroquinone form to be re-oxidized, some intrinsic physicochemical properties were identified from our model (such as a time dependency of the exchanged number of electrons) to characterize such important redox mediators. In this article, the electrochemical behaviour of some substituted quinones (dichloro-; dimethyl-; phenyl) is revisited in aqueous media using chronoamperometry, cyclic and steady-state voltammetry. In particular, the calculation of the number of electrons involved in the hydroquinone/quinone couple may be distorted due to kinetic limitations. A simple model can be used to explain the kinetics differences between the different quinones.image