The electrochemical and spectroelectrochemical properties of the mu-meso(tetrapyridyl)porphyrin iron(III)-tetrakis-{bis(bipyridine)(chloro)ruthenium(II)} complex and of its corresponding mu-oxo dimer have been investigated. Strong Fe-Fe interaction in the mu-oxo dimer has been evidenced by the cathodic shift of the Fe-III/II porphyrin redox potential, by more than 0.9 V in comparison with the monomer species (+0.16 V). Electrostatically assembled films constituted by alternating layers of cationic tetraruthenated and anionic tetrasulphonated iron porphyrins have been elaborated and employed in modified electrodes. These films exhibit the characteristic electrochemical waves associated with the Fe-III/II porphyrin and Ru-III/II(bipy)(2)Cl moieties.