Spectroscopic study of a bis(imidazole) (octaethylporphyrinato)iron(III) complex

Low-spin ferric octaethylporphyrinatoiron complex with two imidazole axial ligands [Fe(III)(OEP)(Im)2]+ has been investigated by electron paramagnetic resonance (EPR) and Mössbauer spectroscopies. It was found that the ground spin state corresponds to the electron configuration (dxy)2 (dxz, dyz)3 and planes of the imidazole axial ligands have a parallel mutual orientation. Ethyl groups bonded to pyrrole rings, as peripheral substituents, effect on the ground electron spin state of the complex studied and the relative orientation of the the imidazole axial ligands in a similar way like the phenyl substituents bonded to meso-carbon atoms of the porphyrin macrocycle. The temperature dependence of the Mössbauer spectra is discussed in terms of magnetic relaxation processes.