An ab initio mo study on the structure dependence of Mösssbauer spectra in iron porphyrin complexes

Abstract

For bis-pyridine(porphinato)iron (FeP(py) 2), the Mössbauer spectral parameters, the quadrupole splitting (QS) and isomer shift (IS), were calculated for various FeN py (N py: pyridine nitrogen) bond distances by using ab initio LCAO SCF MO wave-functions. At the equilibrium FeN py bond distances, QS and IS were in agreement with the experimental values for ferric and ferrous low-spin states. It was found that QS and IS are increasing functions of the FeN py distance for the main configurations of the ground states. From these results, the pressure dependence of the Mössbauer parameters for molecular crystals is qualitatively explained.