INTRAMOLECULAR ANTIFERROMAGNETISM IN 3,7,8,12,13,17,18-OCTAETHYLPORPHYRINATO)IRON(III)]

The magnetism of 3,7,8,12,13,17,18-octaethylporphyrinato)iron(III)] wi th bridge geometry d(Fe-O) = 1.752 Angstrom and measured angle(Fe-O-Fe ) = 178.6 degrees can be explained in terms of antiferromagnetically e xchange coupled iron(III)-3d(5) pairs. The magnetochemical analysis in the temperature range 6 K - 295 K on the basis of the isotropic Heise nberg model (spin Hamiltonian: (H) over cap = -2J (S) over cap(1) .(S) over cap(2), S-1 = S-2 = 5/2) leads to the exchange parameter J = - 1 25 cm(-1). With regard to the Fe-O bond length the J value corresponds to the series of data observed for other mu-oxodiiron-porphyrins and -porphycenes. Compared to the spin-spin coupling in [Fe2Cl6O](2-), \J\ is enhanced by approximate to 10%.