Low-spin ferriheme models of the cytochromes: Correlation of molecular structure with EPR and Mössbauer spectral parameters

The magnetic Mössbauer spectra of a series of low-spin ferriheme complexes have been investigated and compared with their EPR spectral parameters and molecular structures. To date there has been little systematic analysis of either estimated or fitted values of the hyperfine coupling constants for low-spin ferriheme centers and no meaningful correlation has been established between the Mössbauer parameters and the axial ligands of such species. With the results of the present study, we have been able to find correlations of molecular structures with iron-orbital splittings, g-tensor values derived from EPR signals and magnetic hyperfine interaction components A_zz obtained from magnetic Mössbauer spectra. These correlations should be useful to future workers in the field of heme-containing enzymes.