Electrografting of mono-n-boc-ethylenediamine from an acetonitrile/aqueous NaHCO3 mixture

Abstract

The electrografting of primary amines to carbon electrodes is now widely used as a method of electrode modification. Using a mixture of acetonitrile and 0.1 M aqueous NaHCO3 in the ratio 4:1 is shown to significantly improve the efficiency of coupling of mono-N-Boc-ethylenediamine (EDA-Boc) to the surface of glassy carbon over that obtained in acetonitrile alone. In the presence of added NaHCO3 the initial current in cyclic voltammetry is higher, the layer of attached amine forms more rapidly, and the electrode passivates more rapidly. The resulting film of EDA-Boc is shown to be more blocking towards [Fe(CN)6]3- electrochemistry and, following removal of the Boc protecting group and coupling of the free amine to anthraquinone-2-carboxylic acid, a higher surface coverage of the anthraquinone is obtained. Modelling of the voltammetry for the electrograftng reaction using a simple kinetic scheme gives good agreement between the simulated voltammograms and experiment. Comparison of the fitting parameters from the model for the reaction in acetonitrile and in acetonitrile/NaHCO3 shows that the competition between reaction of the amine radicals with the carbon surface and reaction in homogeneous solution is shifted more in favour of the surface reaction in acetonitrile/NaHCO3.

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Identifiers

ORCID for Guy Denuault: orcid.org/0000-0002-8630-9492

ORCID for Philip N. Bartlett: orcid.org/0000-0002-7300-6900

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