Dioxygen binding in iron and cobalt picnic basket porphyrins

1H NMR and oxygen affinity analysis of iron and cobalt picnic basket porphyrins (PBP) reveals that PBPs have high oxygen affinities. Increase in basket size decreases oxygen affinity. Interactions between terminally bound dioxygen and amide protons influence oxygen affinity. The oxygen ligand in Co(II)O2 adducts has a greater electron density than that in Fe(II)O2 adducts.