title: A study of the redox potentials and electron transfer rates of several naturally occurring and synthetic iron porphyrins in DMF.
abstract: The reduction potentials and formal electron transfer rate constants of several iron porphyrins were measured in DMF by the technique of cyclic voltammetry. The ease of each reduction was found to be a function of porphyrin ring basicity and was dependent on the type of electrode reaction. Greatest effects of ring basicity were observed for pi anion radical formation whil smaller effects were obtained for reactions involving the central metal. Electron transfer rate constants for the ferric-ferrous reaction also varied with ring basicity and paralled trends in the redox potentials, that is, the most basic porphyrin yielded the most difficult reduction, both kinetically and thermo-dynamically, while the least basic prophyrin yielded the most facile kinetic and thermodynamic reduction. Based on this data a mechanism of ferric-ferrous electron transfer involving transfer via the pi ring system is proposed.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D004121:Dimethyl Sulfoxide; D004126:Dimethylformamide; D004579:Electron Transport; D007501:Iron; D008665:Metalloporphyrins; D009570:Nitriles; D010084:Oxidation-Reduction; D011048:Polarography; D011199:Potentiometry
chemical_list: D008665:Metalloporphyrins; D009570:Nitriles; D004126:Dimethylformamide; D007501:Iron; D004121:Dimethyl Sulfoxide