Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III)(TPP):Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III)(TPP):Cl molecule leads to signifi cant shortening of Fe-N distances at the fi rst stage of the reduction Fe(III)(TPP):Cl →Fe(II)(TPP) and lengthening of these bonds at the second stage Fe(II)(TPP)→Fe(I)(TPP). Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II) and Fe(I)(TPP) with tetrahydrofuran (THF) solvent is considered. Electron configuration of Fe(II)(TPP) corresponds to intermediate-spin (S = 1) state and in the case of Fe(I)(TPP) low-spin state (S = ½) is observed. Electron density distribution in Fe(II)- and Fe(I)(TPP) complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained

Spectroscopic characteristics of FeI-phthalocyanine

Results of Mössbauer and EPR study of a univalent-iron phthalocyanine complex (FeIPc) are presented in this paper. FeIPc has been obtained from FeIIPc by the chemical reduction method in tetrahydrofuran (THF) and dimethoxyethan (DME) solutions. Like in the case of FeI-porphyrin complexes, Mössbauer and EPR data as well as quantum calculations of electronic absorption spectra confirm in this case a low-spin configuration of FeI ions with an unpaired electron located at dz2 orbital. Interaction between FeIPc and THF molecules does not change significantly the electron configuration of FeI ions coordinated to phthalocyanine ligand

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III)(TPP):Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III)(TPP):Cl molecule leads to signifi cant shortening of Fe-N distances at the fi rst stage of the reduction Fe(III)(TPP):Cl →Fe(II)(TPP) and lengthening of these bonds at the second stage Fe(II)(TPP)→Fe(I)(TPP). Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II) and Fe(I)(TPP) with tetrahydrofuran (THF) solvent is considered. Electron configuration of Fe(II)(TPP) corresponds to intermediate-spin (S = 1) state and in the case of Fe(I)(TPP) low-spin state (S = ½) is observed. Electron density distribution in Fe(II)- and Fe(I)(TPP) complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained

Mechanism of Rotational Hysteresis Energy in Sm-Fe-N Permanent Magnets

Investigations were carried out on Sm-Fe-N permanent magnet produced by the reactive diffusion method with different grain sizes (from 8.6 to 0.97μm). The rotational hysteresis energy has been measured as a function of the applied field. The proposed model of rotational hysteresis energy is in good agreement with the experimental results. It is shown that the magnetization reversal process in Sm-Fe-N magnet is controlled by the nucleation of reversed domains

Effect of nitrogen substitution in porphyrin ring on Mössbauer parameters of iron ions

Electron configuration changes of Fe(III) ions in porphyrin complexes with chloride axial ligands caused by the successive nitrogen substitution of CH methine bridges at meso positions of the porphyrin ring is discussed on the basis of Mössbauer spectroscopy results. It was shown that increase of a number of nitrogen atoms at the meso positions changes the character of quantum-mechanically mixed spin state of Fe(III) ions (S = 5/2 + 3/2) by the increase of the intermediate-spin (S = 3/2) contribution. This feature is reflected in Mössbauer spectra by an increase of quadrupole splitting values and the decrease of the asymmetry of quadrupole doublets, when the number of nitrogen atoms at the meso positions increases. Isomer shifts remain practically unchanged. These peculiarities are discussed in the light of spin relaxation mechanisms and the occupancy of d orbitals in Fe(III) ions coordinated to the porphyrin ring and chloride ligand. It has been noticed that Mössbauer parameters correlate qualitatively with EPR data

Comment on “Stabilization of low-valent iron(I) in a high-valent vanadium(V) oxide cluster”

A recent Communication in this journal reported the stabilization of low‐valent iron(I) in a fully oxidized polyoxovanadate. With no ligand‐field argument to support such an assignment, a re‐evaluation of the data accompanied by detailed computational analysis reveals the redox chemistry is localized to the polyoxovanadate, and when reduced, instigates a spin transition at iron

Univalent iron monoazaetioporphyrin complexes studied by Mössbauer spectroscopy

Results of Mössbauer and EPR studies of univalent-iron monoazaetioporphyrin complexes [Fe(I)(MAEP)] are presented in this paper. Fe(I)(MAEP) were generated using the chemical reduction method. Three forms of the univalent-iron monoazaetioporphyrin complexes were observed: (I) typical Fe(I)(MAEP), (II) with an additional electron on the porphyrin ligand [Fe(I)(MAEP•)]- and (III) the Fe(I)(MAEPh) phlorin structure. Electron configuration of Fe(I) ions in these complexes is (dxy)2(dxz ,dyz)4(dz 2)1. The [Fe(I)(MAEP•)]- structure is stable only in solution and it is transferred into Fe(I)(MAEP) in the solid state. Mössbauer parameters for all products of the reduction reaction are given

Mössbauer Study of a Reduction Process in Iron Azaporphyrins

Electronic structure of the Fe(II)- and Fe(I)-complexes of mono- and diazaporphyrins studied by the Mössbauer spectroscopy is considered in this paper. It was found that in the presence of tetrahydrofuran molecules, the electron configuration of Fe(II) ions in the studied complexes corresponds to the intermediate spin state (S = 1) and the complexation of tetrahydrofuran solvent does not change this state. Interaction of tetrahydrofuran solvent with Fe(I)-azaporphyrins does not influence the electronic structure of Fe(I) ions coordinated to the porphyrin ligand, either. Electron configuration of Fe(I) ions in Fe(I)-octaethylporphyrins and Fe(I)-azaporphyrins is the same: ($d_{xy})^{2}(d_{xz},d_{yz})^{4}(d_{z}^2)^{1}$. The aza substitution is reflected in the values of the Mössbauer parameters. Increasing number of nitrogen atoms at meso positions causes the increase in the quadrupole splittings within the range 1.49-2.24 mm/s for the Fe(II) complexes and within the range 1.35-1.85 mm/s for the Fe(I)-porphyrins. Values of the isomer shifts are decreased from 0.51 to 41 mm/s for the same sequence of the Fe(II) complexes. For the Fe(I) reduced forms the isomer shifts are nearly constant and equal to about 0.37 mm/s. The Mössbauer results are discussed in association with EPR data for Fe(I)-porphyrins

Mössbauer Study of a Reduction Process in Iron Azaporphyrins

Electronic structure of the Fe(II)- and Fe(I)-complexes of mono- and diazaporphyrins studied by the Mössbauer spectroscopy is considered in this paper. It was found that in the presence of tetrahydrofuran molecules, the electron configuration of Fe(II) ions in the studied complexes corresponds to the intermediate spin state (S = 1) and the complexation of tetrahydrofuran solvent does not change this state. Interaction of tetrahydrofuran solvent with Fe(I)-azaporphyrins does not influence the electronic structure of Fe(I) ions coordinated to the porphyrin ligand, either. Electron configuration of Fe(I) ions in Fe(I)-octaethylporphyrins and Fe(I)-azaporphyrins is the same: ($d_{xy})^{2}(d_{xz},d_{yz})^{4}(d_{z}^2)^{1}$. The aza substitution is reflected in the values of the Mössbauer parameters. Increasing number of nitrogen atoms at meso positions causes the increase in the quadrupole splittings within the range 1.49-2.24 mm/s for the Fe(II) complexes and within the range 1.35-1.85 mm/s for the Fe(I)-porphyrins. Values of the isomer shifts are decreased from 0.51 to 41 mm/s for the same sequence of the Fe(II) complexes. For the Fe(I) reduced forms the isomer shifts are nearly constant and equal to about 0.37 mm/s. The Mössbauer results are discussed in association with EPR data for Fe(I)-porphyrins