title: Carbon-13 and proton nuclear magnetic resonance spectroscopy of water-soluble porphyrins and metalloporphyrins.
abstract: Carbon-13 and proton nuclear magnetic resonance (NMR) spectra have been recorded for porphyrins, zinc porphyrins, and iron(III) porphyrin complexes in aqueous media. Spectra of porphyrin-c and hemin-c confirm the structure with thioether linkages at positions alpha to the porphyrin ring. The pattern of NMR isotropic shifts has implications regarding electron transfer in cytochrome-c. Free-base porphyrin-c and meso-substituted porphyrins have been examined for pyrrole nitrogen-hydrogen tautomerism and possible aggregation in aqueous solution. Zinc porphyrin 13C NMR spectra were recorded in order to provide diamagnetic references for paramagnetic iron(III) derivatives. Low-spin iron(III) porphyrin-biscyano complexes in aqueous solution exhibit NMR isotropic shift patterns similar to those previously observed for related compounds in non-aqueous media. The first 13C NMR spectra are reported for mu-oxo-bridged iron(III) porphyrin dimers. A partially resolved spectrum of a high-spin iron(III) porphyrin has also been obtained. Patterns of 13C and proton isotropic shifts are compared, and unpaired spin delocalization mechanisms for 13C resonances are discussed in a qualitative manner.
mesh_terms: D002247:Carbon Isotopes; D006418:Heme; D007501:Iron; D009682:Magnetic Resonance Spectroscopy; D008665:Metalloporphyrins; D011166:Porphyrins; D012995:Solubility; D015032:Zinc
chemical_list: D002247:Carbon Isotopes; D008665:Metalloporphyrins; D011166:Porphyrins; D006418:Heme; D007501:Iron; D015032:Zinc