Journal of Physical Chemistry B, Vol.107, No.26, 6486-6490, 2003
Do the one-electron oxidized derivatives of some six-coordinate low-spin iron(III) porphyrins feature strong metal-ligand ferromagnetic coupling?
It has been recognized for some time that the high-valent complex [Fe(TPP)(1-MeIm)(2)](2+) (TPP = meso-tetraphenylporphyrin, 1-MeIm = 1-methylimidazole) exhibits an S = 1 ground state and has been described as a low-spin Fe(III) porphyrin pi-cation radical with strong metal-porphyrin ferromagnetic coupling. Because strong metal-ligand ferromagnetic coupling is quite unusual, a DFT investigation of two truncated and symmetrized models of this complex, namely, [Fe(P)(Py)(2)](2+) and [Fe(P)(ImH)(2)](2+), was carried out. The results indicate that the ground-state electronic configurations may be described as low-spin Fe(IV)-like, with varying degrees of metal-to-porphyrin spin delocalization, which provides a natural explanation for the experimentalists' somewhat unusual description of the electronic structure of [Fe(TPP)(1-MeIm)(2)](2+).