Reactivity trends of Fe phthalocyanines confined on graphite electrodes in terms of donor-acceptor intermolecular hardness: Linear versus volcano correlations

The figure shows a semilog linear correlation between log k and ΔɛD-A and also versus the Fe(II)/(I). It is clear that the intrinsic reactivity of the Fe complexes for the oxidation of hydrazine increases with the formal potential and with the decrease in the intermolecular hardness since lower hardness corresponds to higher reactivities. So the linear correlation shown in figure, which is independent on the surface concentration of Fe(II) active sites, is a linear free energy relationship.