Electron Transfer Reactions of Cytochrome c Using the Mixed Monolayer Au Electrode Composed of CoIII Complex and Hydroxyl-Terminated Alkanethiols

Abstract

We prepared the mixed monolayer-modified Au electrode composed of negatively charged Co 111 complex (1) and hydroxyl-terminated alkanethiols (C,; n = 2, 6), 1/C,-Au, using the "step-by-step" immobilization method; the low-d~nsity monolayer of 1 (1-Au) was firstly constructed with a spacing and then C, molecules were filled in the gap of 1. In the cyclic voltammetric measurement of horse heart cytochrome c (cyt c) using 1/C2-Au, only a pair of oxidation-reduction wave was observed with almost the same peak separation as the case of 1-Au. Since the electron transfer rate by using the single monolayer of~ was much faster than that of 1-Au, it clearly indicates that the modification ofC 2 does not cause the phase-separation and C 2 molecules on Au do not influence to the electron transfer reaction with cyt c. In contrast, 1/C.,-Au showed faster electron transfer rate than the cases of 1-Au and 1/C 2 -Au, but exhibited slower rate than that of single monolayer of C 6 • These findings indicate that cyt c frrstly interacts with negatively charged 1, and then electron transfer reaction proceeds via C 6 molecules on Au electrode.