⁵⁷Fe Mössbauer Spectroscopy in Chemistry and Biology

Cofactor composition and function of a H2-sensing regulatory hydrogenase as revealed by Mössbauer and EPR spectroscopy

“…This site exhibits a low isomer shift characteristic of low-spin Fe II centers, because shielding of the 57 Fe nucleus is less effective compared to the case of high-spin Fe II centers. 71 , 72 Furthermore, the quadrupole splitting parameter varies between the two different redox states. Upon transition from the oxidized Ni-SI to the one-electron more reduced Ni-C state, the quadrupole splitting Δ E Q decreases from 1.60 mm s –1 to 0.69 mm s –1 , reflecting significant changes in the ligand environment of the Fe II ion, whereas the isomer shift remains almost invariant.…”

Spectroscopic features of cytochrome P450 reaction intermediates

“…In addition, low temperatures and relatively high quantities of the material, i.e. ~0.5 ml of > 0.2 mM 57 Fe atoms [68] are needed for a manageable signal-to-noise ratio; hence, this method has mostly been limited to those microbial P450s where large quantities of material from bacterial expression are available.…”

Understanding Active Sites in Pyrolyzed Fe–N–C Catalysts for Fuel Cell Cathodes by Bridging Density Functional Theory Calculations and 57Fe Mössbauer Spectroscopy

“…Its two Mössbauer parameters are the isomer shift () and the quadrupole splitting energy (E QS ). [18][19][20] These two parameters originate from hyperfine interactions between the iron nucleus and the surrounding electronic environment, and vary therefore with the iron oxidation state, spin state, and its chemical surrounding. 21 Due to the clear different shape and Mössbauer parameters of the spectral signals arising from different Fe structures, the fitting of the experimental spectrum of any Fe-N-C catalyst with a number of spectral components (singlets, doublets and sextets) is usually relatively straightforward and gives direct quantitative information on the fraction of Fe present in different forms.…”

“…Namely, for spectra recorded in the absence of a strong external magnetic field, metallic iron and iron carbides result in sextets (except for the paramagnetic γ-Fe structure, leading to a singlet), whereas the fingerprint of FeN x C y moieties is a quadrupole doublet. Its two Mössbauer parameters are the isomer shift (δ) and the quadrupole splitting energy (Δ E QS ). − These two parameters originate from hyperfine interactions between the iron nucleus and the surrounding electronic environment and vary, therefore, with the iron oxidation state, spin state, and its chemical surrounding …”