Substrate and co-catalyst effects on the local coordination environment of a Fe-porphyrin catalyst

► EPR spectroscopy shows that the system FeR4P/Imid/NaIO4/PCP behaves as an integrated entity with redox potential appropriate for efficient redox cycling of the iron. ► The two binding constants for coordination of imidazoles were estimated using UV-Vis spectroscopy. The binding constant of the second imidazole (K2) was found to be one order of magnitude greater than the first (K1).