Intramolecular Antiferromagnetism in μ‐Oxo‐bis[(5,15‐dimethyl‐2,3,7,8,12,13,17,18‐octaethylporphyrinato)iron(III)]

The magnetism of μ‐oxo‐bis[(5,15‐dimethyl‐2,3,7,8,12,13,17,18‐octaethylporphyrinato)iron(III)] with bridge geometry d(FeO) = 1.752 Å and ∢(FeOFe) = 178.6° can be explained in terms of antiferromagnetically exchange coupled iron(III)‐3d 5 pairs. The magnetochemical analysis in the temperature range 6K–295K on the basis of the isotropic Heisenberg model (spin Hamiltonian: Ĥ = −2 J Ŝ 1 · Ŝ 2 S 1 = S 2 = 5/2) leads to the exchange parameter J = −125 cm −1 . With regard to the FeO bond length the J value corresponds to the series of data observed for other μ‐oxodiiron‐porphyrins and ‐porphycenes. Compared to the spin‐spin coupling in [Fe 2 Cl 6 O] 2− , | J | is enhanced by ≈ 10%.