Molecular dynamics simulations of ferrocene-terminated self-assembled monolayers

The present work describes our studies of the Fc(CH(2))(12)S-/C(10)S-Au monolayers to provide a more detailed molecular description. Molecular dynamics simulations of these mixed monolayers are carried out in conditions close to the electrochemical ones. For this purpose, a supporting electrolyte is added (NaClO(4) 1 M) and the electron transfer process is modeled through molecular simulations of ferrocene both in its neutral (initial state) and oxidized form (final state). The heterogeneity of the surface, that is, "clustered " or "isolated" ferrocene moieties, has been considered for the ferrocenylalkylthiolates using the same grafting densities. The structural properties (density profiles and angular distributions) are described in terms of redox induced orientation changes by comparison between the initial and final states. It is established that this orientation change due to the oxidation of the ferrocene to the ferrocenium is mainly observed in the random system, and it is less pronounced in the cluster system. Finally, the energy contributions underline the role played by the supporting electrolyte.