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 A and ∢(FeOFe) = 178.6° can be explained in terms of antiferromagnetically exchange coupled iron(III)-3d5 pairs. The magnetochemical analysis in the temperature range 6K–295K on the basis of the isotropic Heisenberg model (spin Hamiltonian: Ĥ = −2JŜ1 · Ŝ2S1 = S2 = 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 [Fe2Cl6O]2−, |J| is enhanced by ≈ 10%. Intramolekularer Antiferromagnetismus in μ-Oxo-bis[(5,15-dimethyl-2,3,7,8,12,13,17,18-octaethylporphyrinato)eisen(III)] μ-Oxo-bis[(5,15-dimethyl-2,3,7,8,12,13,17,18-octaethylporphyrinato)eisen(III)] mit der Bruckengeometrie d(FeO) = 1,752 A und ∢(FeOFe) = 178,6° zeigt nach Analyse der magnetischen Suszeptibilitat zwischen 6 K–295 K (Heisenberg-Modell: Ĥ = −2JŜ1 · Ŝ2; S1 = S2 = 5/2) antiferromagnetische Spin-Spin-Kopplung innerhalb der dinuklearen Fe(III)-3d5-Einheit mit J = −125 cm−1. Der J-Wert ordnet sich in bezug auf den FeO-Abstand in die Reihe bekannter μ-Oxodieisen(III)-Porphyrine und -Porphycene ein. Gegenuber der Spin-Spin-Kopplung in [Fe2Cl6O]2− ist |J| um ≈10% erhoht.