Comment: NMR investigation of the electronic properties and magnetic states of hemes and hemoproteins: the S = 2 state in ferrous porphyrins.
The analysis of 1H NMR spectra of the high spin ferrous porphyrin with the axial base inserted in a chain bridged over one of the porphyrin face through opposite phenyl groups has been made. The possible conformational equilibria between rotamers with respect to the Fe- N axial ligand bond have allowed to account for all parameters of NMR spectra including the number of pyrrole resonances and the deviation from the Curie behaviour of the isotropic shift. The conformational model has not allowed to conclude decisively about the electronic ground state. The advantages and restriction of the previously proposed model with the settled position of the pyridine ring where the in-plane rhombic distortion splits the 5E level has also been considered. The influence of the axial ligand position on the spin density distribution has been discussed.
D004563:Electrochemistry; D006418:Heme / Q000032:analysis*; D006420:Hemeproteins / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011789:Quantum Theory
D006420:Hemeproteins; D006418:Heme