ID and 2D1H NMR studies of iron(III) complexes on geoporphyrins of the deoxophylloerythroetio structural type derived from oil shale
作者:
Stanisaw Wototwiec,
Lechostaw Latos‐Gražyński,
Olga V. Serebrennikova,
Franciszek Czechowski,
期刊:
Magnetic Resonance in Chemistry
(WILEY Available online 1995)
卷期:
Volume 33,
issue 1
页码: 34-43
ISSN:0749-1581
年代: 1995
DOI:10.1002/mrc.1260330108
出版商: John Wiley&Sons, Ltd.
关键词: NMR;1H NMR;Oil shale geoporphyrin;Iron porphyrin complexes;Deoxophylloerythroetioporphyrin
数据来源: WILEY
摘要:
AbstractOne‐ and two‐dimensional1H NMR studies of low‐spin iron(III) geoporphyrins derived from the deoxophylloery‐throetioporphyrin series (the oil shale source) resulted in an unambiguous assignment of all resonances. Deoxophylloerythroetioporphyrin (DPEP) and its 17‐desethyl homologue were isolated from dictyonema shale as vanadyl complexes. They were demetallated and subsequently converted into iron(III) porphyrins under mild conditions. The 17‐propionic methyl ester analogue, i.e. deoxophylloerythrin methyl ester, was synthesized for comparative studies. A spectroscopic probe to identify iron(III) isocyclic porphyrins was established. The five‐membered isocyclic ring induced considerable asymmetry in the spin density distribution at the 3eπbonding orbitals, placing the unpaired electron on the dxzorbital located along the N‐21—N–23 axis. The temperature dependence of the hyperfine shift is consistent with the thermal equilibrium between two non‐degenerated electronic states (dxz)2(dyz)1↔(dxz)1(dyz)2. The new structural factor generating the asymmetric spin density distribution in low‐spin iron(III) porphyrin complex was determined. The hyperfine shift pattern of high‐spin iron(III) isocyclic geoporphyrins provided useful probes for their detection in iron geoporphyrin mixtures by1H NMR prior to their separation. Valuable information is derived from the number of observed signals ofmeso‐protons and characteristic, extremely downfield resonances of isocyclic ring hydrogens. Both features may be useful for the spectral identification of iron(III) porphyrins of the DPEP series from geological mate
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