Toward a prediction of the redox properties of electroactive SAMs: a free energy calculation by molecular simulation.
We report free energy calculations of FcC(6)S-/C(4)S-Au and FcC(6)S-/C(12)S-Au binary self-assembled monolayers (SAMs) formed by one ferrocenylhexanethiolate chain and alkylthiolate chains. We demonstrate that the free energy perturbation methods are able to reproduce the positive shift of the redox potential when the coadsorbed butanethiolate C(4)S chains are replaced by dodecanethiolate C(12)S chains. The different contributions to the Ewald summation involved in the perturbation process are thoroughly described. We complete the study by a microscopic description of the binary SAMs before and after oxidation. The molecular dynamics (MD) simulations evidence that the formation of the ion-pair between the ferricinium and a single perchlorate anion of the supporting electrolyte is more favored in FcC(6)S-/C(12)S-Au SAM.
Filippini
Gaëlle
G
Clermont Université, Université Blaise Pascal, Laboratoire de Thermodynamique et Interactions Moléculaires, UMR CNRS 6272, BP 10448, F-63000 Clermont-Ferrand, France.
Goujon
Florent
F
Bonal
Christine
C
Malfreyt
Patrice
P