Study of electronic structure of spin-transition complexes by XPS and Mössbauer spectroscopy

Abstract

Two groups of iron(II) complexes with 1,2,4-triazoles have been studied by XPS and Mössbauer spectroscopy. In the first group, iron atoms in the high spin state ( S =2) were considered, and in the second group, atoms in the low spin state ( S =0). Essential changes in the Fe 2p and Fe 3s spectra were observed in going from the one group of complexes to the other, whereas the N 1s spectra were unchanged. The Fe 2p 3/2 binding energy for the low spin state complexes was shown to be 708.3–708.8 eV, and for the high spin state 710.2–711.0 eV. In the Fe 2p and Fe 3s spectra of the high spin complexes, multiplet and satellite structures are revealed. As a result of the analysis of experimental XPS and Mössbauer chemical shifts, we conclude that the ionicity of Fe–N chemical bonds in the high and low spin complexes is connected to the higher occupation of the 4s orbitals of the iron atom in the second group of compounds.