Redox potential selection in a new class of dendrimers containing multiple ferrocene centers

The preparation and electrochemical properties of four new dendrimers, compounds 1, 2, 3, and 4, containing eight, seven, four, and four ferrocene residues, respectively, are described. These small dendrimers were prepared with the building block bis(ferrocenylmethyl)alkylamine, which contains the tether -CH2-N(R)-CH2- linking two ferrocene units. The resulting dendrimers are multiferrocene compounds in which the peripheral ferrocene residues are paired. Partial protonation or N-methylation of the connecting nitrogen atoms allows the selection of the ferrocene oxidation potentials between two different values (similar to0.4 and similar to0.6 V vs Ag/AgCl). The observed voltammetric pattern for ferrocene oxidation can be reversibly switched among several states depending on the number of protonated centers within each dendritic structure. Crystallographic and electrochemical data confirm that the electronic communication between two equivalent ferrocene centers is lessened after protonation or N-methylation of the connecting nitrogens.