The activation and functionalization of hydrocarbons will be studied, using an iron porphyrin complex at the catalyst, molecular oxygen as the oxidant, and a stoichiometric co-reductant and proton source. The axial substituent in the iron porphyrin complex will be a pyridone, which functions either as a neutral or an anionic ligand depending on degree of protonation. The reduction of the iron (III) complex by proton-coupled electron transfer, and the ability of the resulting iron (II) complex to bind dioxygen, will be investigated. Deprotonation of a p-hydroxyanilinium salt activates it toward the loss of an electron. The resulting semquinone intermediate can, in theory, convert the iron (III) superoxide formed upon oxygen binding to an iron (III) hydroperoxide. Tautomerization of this complex, followed by loss of water, would generate an iron (IV) (porphyrin radical) oxo complex, analogous to those involved in oxidations by cytochrome P-450. The porphyrin ligand will be design with 3-hydroxyindenone substituents that facilitate these two steps. The decreased basicity of the axial ligand in this high-valent complex would disfavor protein transfer from the reducing agent, thus avoiding the unproductive reaction of reducing agent with the highly oxidizing intermediate.
