TY - JOUR
T1 - 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
AU - Polam, Jayapal Reddy
AU - Wright, Joshua L.
AU - Christensen, Kenner A.
AU - Walker, F. Ann
AU - Flint, Holger
AU - Winkler, Heiner
AU - Grodricki, Michael
AU - Trautwein, Alfred X.
PY - 1996/6/5
Y1 - 1996/6/5
N2 - We have prepared a series of 94.5%-enriched 57Fe(II) complexes of tetramesitylporphyrin and octaethylpoiphyrin having various bis- or mixed axial ligation and investigated them by both NMR and Mössbauer spectroscopy. The results obtained, and literature values for MbCO and cytochrome c, show a rough correlation between ΔEQ and δFe. This correlation suggested that the previously-reported chemical shifts of the complexes [TPPFeL2], L = pyridine-d5, and pyrrolidine (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 the signal of the bis-pyridine-d5 complex at 11 715 ppm, within its predicted chemical shift range, based upon the δFe vs ΔEQ correlation, and ∼4,400 ppm to lower shielding than originally reported. These findings emphasize the value of the Mössbauer - NMR correlation in aiding the detection of 57Fe NMR signals, as well as the perils of seeking these easily "folded" signals without such a correlation.
AB - We have prepared a series of 94.5%-enriched 57Fe(II) complexes of tetramesitylporphyrin and octaethylpoiphyrin having various bis- or mixed axial ligation and investigated them by both NMR and Mössbauer spectroscopy. The results obtained, and literature values for MbCO and cytochrome c, show a rough correlation between ΔEQ and δFe. This correlation suggested that the previously-reported chemical shifts of the complexes [TPPFeL2], L = pyridine-d5, and pyrrolidine (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 the signal of the bis-pyridine-d5 complex at 11 715 ppm, within its predicted chemical shift range, based upon the δFe vs ΔEQ correlation, and ∼4,400 ppm to lower shielding than originally reported. These findings emphasize the value of the Mössbauer - NMR correlation in aiding the detection of 57Fe NMR signals, as well as the perils of seeking these easily "folded" signals without such a correlation.
UR - http://www.scopus.com/inward/record.url?scp=0029977389&partnerID=8YFLogxK
U2 - 10.1021/ja954096m
DO - 10.1021/ja954096m
M3 - Journal articles
AN - SCOPUS:0029977389
SN - 0002-7863
VL - 118
SP - 5272
EP - 5276
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 22
ER -
