title: Carbon-13 nuclear magnetic resonance spectroscopy of high-spin iron(III) porphyrin compounds.
abstract: 13C nuclear magnetic resonance spectra have been obtained for a variety of high-spin iron(III) porphyrin compounds and corresponding mu-oxo-bridged dimeric species. Large hyperfine shifts and significant line broadening are observed. The monomeric complexes exhibit hyperfine shifts which are downfield with the exception of an upfield shift for the meso-carbon atom. Possible unpaired spin delocalization mechanisms and prospects for observing 13C NMR porphyrin resonances in high-spin ferrihemoproteins are discussed. Spectra reported here provide strategy for incorporation of 13C labels in hemoproteins either by biosynthetic or chemical means. The vinyl-CH2 resonances of iron(III) protoporphyrin IX located 260 parts per million downfield from tetramethylsilane are especially attractive from the standpoint of chemical labeling.
mesh_terms: D002247:Carbon Isotopes; D005290:Ferric Compounds; D006420:Hemeproteins; D009682:Magnetic Resonance Spectroscopy; D011166:Porphyrins; D011524:Protoporphyrins
chemical_list: D002247:Carbon Isotopes; D005290:Ferric Compounds; D006420:Hemeproteins; D011166:Porphyrins; D011524:Protoporphyrins