How many ferrocene units of multi-ferrocenyl complexes can react with the electrode?

Ferrocenylcarboxylic acid Fe, Co, and Ni complexes were synthesized as model complexes to investigate how many ferrocene units of multi-ferrocenyl system can react with the electrode. The molecular structures of model complexes were characterized by X-ray single-crystal diffraction, the diffusion coefficient of the complexes and ferrocene was determined by the diffusion-ordered spectroscopy and Einstein–Stokes equation, the electrode reaction numbers of ferrocene units were determined by cyclic voltammetry and the Randles–Sevcik equation. A model of electrode reaction of multi-ferrocenyl system was proposed in this paper, which was used to explore how many ferrocene units of multi-ferrocenyl complexes can react with the electrode.