Paramagnetic NMR spectroscopy is a unique technique for the study of the electronic structures of iron porphyrins.Under favorable conditions,the sign of contact shifts can differentiate between σand π spin delocalization mechanisms and provide important information about bonding interactions between iron and ligands and the electronic nature of iron porphyrin complexes.However it is not always an easy task to isolate contact term from paramagnetic shift especially for 13C NMR data.