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Model Fe(Iii) Porphyrin Systems: Axial Ligation In Oxidized Cytochrome P-450.S, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, S. C. Tang, S. Koch, R. H. Holm
Model Fe(Iii) Porphyrin Systems: Axial Ligation In Oxidized Cytochrome P-450.S, G. C. Papaefthymiou, Richard B. Frankel, S. Foner, S. C. Tang, S. Koch, R. H. Holm
Physics
In an effort to develop useful experimental criteria to distinguish among the viable axial ligation possibilities of O, N, and S coordination in oxidized cytochrome P-450. S (substrate-bound, high-spin), syntheticmodel compounds with O-(Fe(PPIXDME) (OEt) and Fe(PPIXDME) (OC6H4NO2)) and S-(Fe(PPIXDME) (S6H4NO2) and Fe(OEP) (SPh)) donor axial ligands were prepared and studied by Mössbauer spectroscopy. Ferric hemoglobin and myoglobin were used as model compounds with N-axial coordination. The isomer shifts (δ) and quadrupole splittings (ΔEQ) observed are typical of high-spin Fe(III) porphyrins and are comparable with results …
Synthetic Analogs Of The Active Sites Of Oxidized And Reduced Rubredoxin, Richard B. Frankel, G. C. Papaefthymiou, R. W. Lane, R. H. Holm
Synthetic Analogs Of The Active Sites Of Oxidized And Reduced Rubredoxin, Richard B. Frankel, G. C. Papaefthymiou, R. W. Lane, R. H. Holm
Physics
The bischelate monoanion [Fe((SCH2)2C6H4)2]1- contains an unconstrained, near-tetrahedral Fe(III)-S4 coordination unit (similar to the Fe-S4 coordinationunit occurring in rubredoxin proteins) and exhibits the Fe(III)/Fe(II) redox couple. Mossbauer parameters at 77 K are isomer shift δ = 0.13 mm/s (relative to iron metal) and electric quadrupole splitting ΔEQ = 0.57 mm/s. Application of an external magnetic field parallel to the direction of observation at 4.2 K induces a saturation magnetic hyperfine field of - 380 kOe. Upon reduction to the dianion [Fe((SCH2)2C …
Abstract: Mössbauer Spectroscopy Of Pdh Fe Alloys, M. Weber, C. R. Abeledo, Richard B. Frankel, Brian B. Schwartz
Abstract: Mössbauer Spectroscopy Of Pdh Fe Alloys, M. Weber, C. R. Abeledo, Richard B. Frankel, Brian B. Schwartz
Physics
Large changes in the electron susceptibility of PdH alloys have been observed with increasing H concentration, with important consequences for the magnetic and superconducting properties of these alloys. (1) To observe the effect of the changing spin susceptibility, we have studied PdH Fe alloys with 2, 1 and < 0.1 at. % Fe by Mössbauer spectroscopy in external magnetic fields. Mydosh (2) has reported spin glass behavior in the high Fe concentration alloys and Kondo phenomena in the dilute Fe alloys. For hydrogen-metal ratios < 0.5, α and β phases, with low and high hydrogen content respectively, coexist. For temperatures below Tc of the α phase but above Tc of the β phase, we observe a superposition of a six line spectrum and a single line corresponding to the α and β phases respectively. (3) In an applied field, the β phase magnetizes and both phases have hyperfine fields which extrapolate to …
Mössbauer And Nmr Studies Of Site Substitution And Magnetic Structure Of Fe3-XMnXSi Alloys, K. Raj, V. Niculescu, T. J. Burch, J. I. Budnick, Richard B. Frankel
Mössbauer And Nmr Studies Of Site Substitution And Magnetic Structure Of Fe3-XMnXSi Alloys, K. Raj, V. Niculescu, T. J. Burch, J. I. Budnick, Richard B. Frankel
Physics
The NMR measurements in Fe3−xMnxSi alloys show increasingly complex spectra for x > 0.75 due to overlapping signals from Fe, Si and Mn nuclei in various sites. Mössbauer experiments were undertaken to identify the Fe57 resonances. The combined NMR and Mössbauer results have been used to elucidate the site substitution and magnetic structure of these alloys for (0 < x < 1.75).
Metamagnetism In Single Crystal Γ-Co(Pyridine)2Cl2, S. Foner, Richard B. Frankel, W. M. Reiff, H. Wong, Gary J. Long
Metamagnetism In Single Crystal Γ-Co(Pyridine)2Cl2, S. Foner, Richard B. Frankel, W. M. Reiff, H. Wong, Gary J. Long
Physics
Small (≤1 mg) single crystals of γ-Co(pyr)2Cl2 have been grown and measurements of magnetic moment vs applied field H and temperature have been made for 0≤H≤54 kG and 1.25 K≤T≤4.2 K. At 1.25 K, metamagnetic transitions are observed along the a-axis at ~700 G; along the b-axis at both ~800 and ~1500 G; and along the c-axis at ~4 kG. The low field susceptibilities show a maximum at T≃3.4 K for each orientation. Magnetic saturation is not achieved at 54 kG; about 2.5 µB is achieved along the a*- or b-axes, whereas a lower moment is …
Hyperfine Interactions In Antiferromagnetic Eute Using The Te-125 Mossbauer Resonance, N. A. Blum, Richard B. Frankel
Hyperfine Interactions In Antiferromagnetic Eute Using The Te-125 Mossbauer Resonance, N. A. Blum, Richard B. Frankel
Physics
Europium telluride crystallizes in the NaCl structure and is antiferromagnetic with a Néel temperature TN of 9.6 K. We have used the 35.5 keV Møssbauer transition in Te-125 to examine the nature of the spontaneous magnetic moment which has been observed in conducting samples below TN. At 80 K the Mössbauer resonance spectrum consisted of a single absorption line comparable in width with the spectrum of nonmagnetic cubic ZnTe, indicating the absence of a significant quadrupole splitting at this temperature. At 4.2 K the line-width increased by a factor of 1.5, which is equivalent to a single magnetic hyperfine field …
Model System Studies Of Axial Ligation In The Oxidized Reaction States Of Cytochrome P-450 Enzymes, R. H. Holm, S. C. Tang, S. Koch, G. C. Papaethymiou, S. Foner, R. B. Frankel, J. A. Ibers
Model System Studies Of Axial Ligation In The Oxidized Reaction States Of Cytochrome P-450 Enzymes, R. H. Holm, S. C. Tang, S. Koch, G. C. Papaethymiou, S. Foner, R. B. Frankel, J. A. Ibers
Physics
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