Kinetic Separation of Amperometric Responses of Composite Redox-Active Monolayers Assembled onto Au Electrodes: Implications to the Monolayers' Structure and Composition

Abstract

Chronoamperometry provides a sensitive method to elucidate the composition and properties of complex redox-active monolayers assembled onto Au electrodes. Chronoamperometry is applied to characterize a redox-active monolayer composed of a bisdiaminobenzoquinone dyad. The different distances of the quinone units in respect to the electrode yield different electron-transfer rate constants, k1 = 25.3 s-1 and k2 = 1.05 s-1, and the surface coverage of the two quinone units is estimated to be ΓQ1 = 6.5 × 10-11 mol cm-2 and ΓQ2 = 6.5 × 10-11 mol cm-2. The surface densities of the quinone units coincide nicely with those obtained by voltammetric analysis of the monolayer during the steps of its assembly. Similarly, a binary monolayer consisting of bipyridinium and anthraquinone redox-active units was characterized by chronoamperometry. The electron-transfer rate constant to the bipyridinium and anthraquinone components corresponds to k1 = 503 s-1 and k2 = 62 s-1, respectively, and the surface coverage of the red...