ELECTRON-TRANSFER STUDY AND SOLVENT EFFECTS ON THE FORMAL POTENTIAL OF A REDOX-ACTIVE SELF-ASSEMBLING MONOLAYER

Solvent effects on the formal potential of the redox-active self-assembling system [Os(bpy)2(dipy)Cl]1+ (bpy, 2,2'-bipyridine; dipy, 4,4'-trimethylenedipyridine) have been studied in six organic solvents and aqueous solutions. Cyclic voltammetry was used to determine surface coverage and formal potentials and the coulostatic technique (charge injection) to determine double-layer capacitance. The variation of the formal potential with solvent and surface coverage is analyzed within the context of surface activity coefficients. The results seem to indicate that ion-pair formation between perchlorate anions (from supporting electrolyte) and the cationic head groups strongly influences the energetics of the system. An estimate of the standard rate constant for the electron transfer in aqueous solution reveals a very fast electron transfer with a lower limit of the order of 10(5) s-1.