Iron porphyrins with a hydrogen bonding cavity: effect of weak interactions on their electronic structure and reactivity

The electronic structure and reactivity of iron porphyrin complexes bearing 2nd sphere hydrogen bonding residues have been investigated over the last few years. The presence of these weak interactions alters the spin ground state, and axial ligand bonding and provides a proton translocation pathway into the active site. Mechanistic investigations in organic as well as aqueous media demonstrate how controlled delivery of protons is fundamental in dictating the selectivity of a multi-electron multi-proton process like the reduction of dioxygen to water.