Proton NMR dipolar relaxation by delocalized spin density in low-spin ferric porphyrin complexes

Stephen W. Unger, Thomas Jue, Gerd N. La Mar

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Abstract

The proton NMR spin-lattice relaxation of methyl groups in a series of low-spin ferric, S = 1 2 porphyrin complexes has been analyzed in terms of the paramagnetic influences. The differential porphyrin methyl spin-lattice relaxation rates and the dependence of the difference on the methyl contact shift patterns dictate that both ligand-centered as well as iron-centered dipolar relaxation by unpaired spin density must be considered. For the systems considered, the relaxation by delocalized spin density dominates methyl relaxation for contact shifts greater than 19 ppm. The study shows that delocalized dipolar relaxation must be included in any analysis of differential relaxation data in terms of structure in hemoproteins.

Original languageEnglish (US)
Pages (from-to)448-456
Number of pages9
JournalJournal of Magnetic Resonance (1969)
Volume61
Issue number3
DOIs
StatePublished - Feb 15 1985

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