Synthesis and Characterization of "Picnic-Basket" Porphyrins with a Substituent in the Interior of the Pocket

"Picnic-basket" porphyrins of a new type, that have a substituent in the interior of the pocket, were synthesized to study stabilization of the bound oxygen in hemoprotein models. Though these Co(II) porphyrins have enormous equilibrium constants for the formation of base adducts, hydrogen-bonding interaction with coordinated dioxygen is not as effective for stabilization of the metal-dioxygen bond as we had expected. The results suggest that doming of the porphyrin plane plays an important role in the binding of dioxygen.