Complexes utilized by Hedman, Hodgson, and Solomon94 for electronic structure studies on “picket-fence” oxy-heme adduct: (A) the “picket-fence” oxy heme complex with axially coordinated 1-MeIm, (B) [(TpivPP)FeII(1-MeIm)2], (C) [(TpivPP)FeII(1-MeIm)(CO)], (D) [(TPP)FeIII(Im)2](Cl), and (E) [(TpivPP)FeII]. See text for further discussion.