The quantitative evaluation of the effect of an insulating dendritic shell on the redox properties of an embedded iron porphyrin core has been achieved for the first time using water-soluble dendritic iron porphyrins with tethered axial ligands (shown schematically). Thus, these complexes, whose redox properties have been determined by chemical and electrochemical methods in solvents of different polarity (CH(2)Cl(2), MeCN, H(2)O), are valid mimics for cytochromes.