Hyperfine Shifts of the 13C‐NMR. in low spin iron(III) porphyrin complexes

The 13C‐NMR. in Zn(II)(Porphin), Fe(III)(Porphin)(CN2), Zn(II)(Tetraphenyl‐porphin), and Fe(III)(Tetraphenylporphin)(CN2) have been identified, and the 13C hyperfine shifts in the iron complexes evaluated. It was found that dipole‐dipole coupling with the electron spin localized in the π‐orbitals of the aromatic carbon atoms makes an important contribution, to the 13C hyperfine shifts. In a preliminary analysis the experimental spin density distribution obtained from the combined 1H‐ and 13C‐NMR.‐data is compared with theoretical models of the iron porphyrin complexes.