Electrochemical attachment of a conjugated amino–ferrocifen complex onto carbon and metal surfaces

The attachment of a π-conjugated amino–ferrocifen complex was electrochemically achieved either by direct oxidation of the amino group or via the oxidation of the ferrocene moiety. In the first case, the modification consists in oxidizing, at +0.70 V/SCE, the amino moiety to its radical cation, which upon deprotonation from the amino group, yields an aminyl radical that may add onto the electrode surface. Alternatively, it is demonstrated that the amine moiety can be indirectly oxidized through an intra-molecular electron transfer from the amino moiety to the ferrocenyl group after oxidation of the ferrocene part at +0.40 V. This can occur thanks to the conjugated π system of the complex. More importantly, it is demonstrated that the covalent attachment of the complex can be achieved on glassy carbon, gold, and platinum surfaces whatever the approach used. The possible mechanisms for the covalent attachment are discussed. Interestingly, it is also shown that the amino–ferrocene compound adsorbs very well likely via π stacking between grafted and non-grafted molecules. Nevertheless, the adsorbed molecules could be easily removed after passing the electrode in an ultrasonic bath. The electrode coverage was determined under various conditions by integration of the corresponding voltammograms.