Electron-withdrawing or -donating groups are known to directly affect the Fe(III/II) formal potential of ferrocene derivatives by affecting their energy levels relative to the vacuum level. However, perhaps surprisingly, also more subtle indirect “tuning” of the formal potential is possible by changing the “dielectric environment”. This is demonstrated here by systematically changing the chain length of alkyl-chain derivatives. The resulting formal potentials are shown to be correlated to the hydrophobicity of the ferrocene molecule which can be used to predict the redox potential of a ferrocene.