Magnetic and spectroscopic probes for FeOFe linkages in hemin systems

Magnetic and spectroscopic properties of μ-oxo-bis-hemins from natural and structurally related porphyrins were investigated as probes for ascertaining the presence or absence of FeIII-O-FeIII linkages between hemin moieties of hemeproteins. Magnetic susceptibilities of solids from 2.2 to 293 °K were investigated. The data fit the temperature variations expected for a pair of antiferromagnetically coupled S=52, iron(III) porphyrins with J values of