Valence Electron Cloud Asymmetry from Two Points of View: A Correlation between Mössbauer Quadrupole Splittings and 57Fe NMR Chemical Shifts of Diamagnetic Iron(II) Porphyrinates
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- 作者：Jayapal Reddy Polam ; Joshua L. Wright ; Kenner A. Christensen ; F. Ann Walker ; Holger Flint ; Heiner Winkler ; Michael Grodzicki ; and Alfred X. Trautwein
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：June 5, 1996
- 年：1996
- 卷：118
- 期：22
- 页码：5272 - 5276
- 全文大小：126K
- 年卷期：v.118,no.22(June 5, 1996)
- ISSN：1520-5126
文摘
We have prepared a series of 94.5%-enriched57Fe(II) complexes of tetramesitylporphyrin andoctaethylporphyrin having various bis- or mixed axial ligation and investigatedthem by both NMR and Mössbauerspectroscopy. The results obtained, and literature values for MbCOand cytochrome c, show a rough correlationbetween 
EQ and 
Fe. Thiscorrelation suggested that the previously-reported chemical shifts ofthe complexes[TPPFeL2], L = pyridine-d5, andpyrrolidine (Nozawa, T.; Sato, M.; Hatano, M.; Kobayashi, N.; Osa, T.Chem.Lett. 1983, 1289) might be incorrect;we have thus used the rapid pulsing method of Schwenck to detect thesignalof the bis-pyridine-d5 complex at 11 715 ppm,within its predicted chemical shift range, based upon theFe vsEQcorrelation, and ~4,400 ppm to lower shielding than originallyreported. These findings emphasize the value of theMössbauer-NMR correlation in aiding the detection of57Fe NMR signals, as well as the perils of seekingtheseeasily "folded" signals without such a correlation.
EQ and Fe. Thiscorrelation suggested that the previously-reported chemical shifts ofthe complexes[TPPFeL2], L = pyridine-d5, andpyrrolidine (Nozawa, T.; Sato, M.; Hatano, M.; Kobayashi, N.; Osa, T.Chem.Lett. 1983, 1289) might be incorrect;we have thus used the rapid pulsing method of Schwenck to detect thesignalof the bis-pyridine-d5 complex at 11 715 ppm,within its predicted chemical shift range, based upon theFe vsEQcorrelation, and ~4,400 ppm to lower shielding than originallyreported. These findings emphasize the value of theMössbauer-NMR correlation in aiding the detection of57Fe NMR signals, as well as the perils of seekingtheseeasily "folded" signals without such a correlation.