J. Blomquist

X-ray photoelectron and mössbauer spectroscopy on a variety of iron compounds

Abstract A combination of X-ray photoelectron spectroscopy (ESCA) and Mossbauer spectroscopy has been used to study the chemical shifts of a series of iron complexes. Obtained experimental data will constitute a basis for comparison with theoretical studies.

Interpretation of the 57Fe Isomer Shift by Means of Atomic Hartree–Fock Calculations on a Number of Ionic States

The Hartree–Fock method is used to calculate the values of | Ψ(0) |2 for a number of configurations of different Fe ions. An interpolation formula for | Ψ(0) |2 as a function of the occupation number of valence electron orbitals (3d, 4s, 4p) is given. Experimental Mossbauer isomer shifts are correlated to estimated configurations which are compared to available MO calculations for a few cases.

Studies of some iron dithiolate complexes by the ESCA, Mössbauer and extended Hückel methods

Abstract Iron dithiolate complexes have been studied by Mossbauer and ESCA spectroscopy. Atomic charges and iron atom populations have been evaluated. Molecular orbital calculations have been made using the iterative extended Huckel method. The theoretical results are compared with the experimentally obtained charge distributions.

Electrochemical and mössbauer investigations of polymeric iron phthalocyanine oxygen electrodes

Abstract Polymeric iron phthalocyanine precipitated on activated carbon has been heated to temperatures in the range 200–500° C and the catalytic activity for the electrochemical reduction of oxygen has been investigated. The catalysts were tested in porous, hydrophobic electrodes. Mossbauer spectra have been obtained for the catalyst powders exposed to different heating temperatures. Heat treatment was found to give electrodes with a higher rate of deactivation for the electrochemical reduction. This was particularly the case for heat treatments at temperatures higher than 300°C. An increase in the intensity of a doublet in the Mossbauer spectra corresponding to oxidized iron was obtained for the heat treated samples. This increase of oxidized iron was found to be correlated to the increased rate of deactivation for the electrodes.

Mössbauer measurements on iron phthalocyanines

Abstract Monomeric and polymeric iron phthalocyanines (FePc) with and without carbon support and subjected to various heat treatments have been studied by Mossbauer spectroscopy. Dispersing FePc on carbon changes the electronic state of the monomer to low spin (S = 0) while the electronic state of the polymer remains unchanged (S = 1). It is suggested that the bonding between polymeric FePc and carbon takes place through the side groups present on the peripheral parts of the polymer and/or through suitable chemical groups present on the carbon surface. The electron-attracting ability of the side-groups deduced from the Mossbauer spectra is discussed. The results will form a basis for a comparison with data from electrochemical measurements.

Pyrolysis behaviour of metalloporphyrins. Part 2.—A mössbauer study of pyrolysed FeIIItetraphenylporphyrin chloride

FeIII tetraphenylporphyrin chloride (FeCITPP) has been pyrolysed at different temperatures (450–850 °C) for different lengths of time (10–260 min). Some of the samples were mixed with carbon black in a 50/50 (w/w) proportion. Mossbauer spectra were obtained for these catalyst powders. The spectra reveal a number of different sites, occurring with different relative abundance depending on the pretreatment. XPS and electrochemical measurements have also been performed using the same samples. The electrocatalytic properties can be described as a function of the abundance of the various sites and the XPS data were used to support the interpretation.

ESCA and Mössbauer spectra of some iron(III) betadiketonates and tetraphenylporphyrin iron(III) chloride

Abstract X-ray photoelectron spectra and Mossbauer spectra have been recorded for the complexes Fe(1-phenyl-1,3-butanedionate) 3 , Fe(1,3-diphenyl-1,3-propanedionate) 3 , Fe(3-phenyl-2,4-pentanedionate) 3 and meso-tetraphenylporphyrin iron(III) chloride. As an auxiliary tool in the study the IR absorption intensity of the ν CH vibrations of the phenyl groups present in the complexes was measured. By a combination of the XPS binding energies and the IR intensities with previously established relations between these entities and the effective charge of atoms and groups, a rather complete napping of the charge distribution of the complexes was achieved. By a combination of the XPS data with the Mossbauer data is was possible to describe the electron population in the (3rd, 4s, 4p) orbitals of the central iron atom.

Simultaneous electrochemical and mössbauer measurements on polymeric iron phthalocyanine oxygen electrodes

Abstract Mossbauer spectra have been obtained on porous, hydrophobic electrodes in situ when used as oxygen reduction electrodes in sulphuric acid electrolyte. The electrodes consisted of polymeric iron phthalocyanine precipitated on activated carbon. Mossbauer spectra were also obtained on the same kind of electrodes which had been used for different amounts of time. The polymeric iron phthalocyanine was prepared using iron enriched in 57 Fe to get resolvable spectra. The Mssbauer spectra are characterized by the increase of a signal corresponding to oxidized iron as the catalytic activity decreases. A correlation between the amount of iron dissolved into the electrolyte and the electrode potential is seen during the first 100 h of operation. It is suggested that Fe(II) is oxidized to Fe(III) which is dissolved into the electrolyte.

Esca, mössbauer and infrared spectroscopic investigations of a series of tin complexes

Abstract Core electron binding shifts have been measured for a series of tin complexes. From earlier proposed relations between binding energies, infrared intensities and the charge on the ligands we have estimated the effective charge on the tin atom. Also the isomer shifts of the central atom have been measured. By using a sample model for the interpretation of these data in terms of occupation numbers of the valence orbitals, an estimate of the electronic structure of the complexes is obtained.

Use of the Mössbauer isomer shift and the X-ray emission Kα shift to estimate the effective electronic population of iron in complexes

Abstract The Hartree-Fock method is used to calculate the K α transition energy for a number of configurations of different Fe ions. Experimental X-ray emission K α shifts are combined with Mossbauer isomer shifts to estimate the effective configurations of the iron ion.