Tuning the thermodynamic onset potential of electrocatalytic O2 reduction reaction by synthetic iron-porphyrin complexes.

A porphyrin ligand with two β-pyrrolic electron withdrawing ester groups is synthesized and its Co complex is crystallographically characterized. The iron complex of this porphyrin ligand shows an ∼200 mV positive shift in its Fe(III/II) potential in organic as well as aqueous solvents and in the onset potential of ORR relative to that of an unsubstituted porphyrin.