Environment effect on the redox properties of Self-Assembled Monolayers: a theoretical investigation of the nature of the supporting electrolyte

Abstract

Gibbs free energy calculations have been performed to calculate the change in the simulated redox properties of FcC₆S–/C₁₂S–Au and FcC₆S–/C₄S–Au in three different electrolytes (NaClO₄, Na₂SO₄ and NaPF₆). The effect of surface ion association between the ferricinium cation and the electrolyte anions is investigated on the redox properties of SAMs. The microscopic description of the binary SAMs before and after oxidation indicates that the formation of surface ion pairs is strongly correlated with the hydration energy of the corresponding anion. The correlation between the desolvation of the anions and the ion-pairs formation is established. We have shown from the energy contributions that a general understanding of the thermodynamic behavior of these systems should be analyzed in the context of the enthalpy–entropy compensation effect.