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

The magnetic Mossbauer 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 Mossbauer 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 Mossbauer spectra. These correlations should be useful to future workers in the field of heme-containing enzymes.