Börje Folkesson

On the core electron binding energy of carbon and the effective charge of the carbon atom

From Mulliken population data based on ab initio calculations of a series of substituted aromatic compounds and from well-calibrated XPS data (core electron binding energies, Eb) an empirical relation between Eb(C1s) and the charge on the carbon atoms, qc, has been found: Eb(C1s = 6.42qc + 4.52q2c + 285.8 (eV). It is also found that XPS data for other carbon-containing species, notably the cyanide ion, can be described by this relation.

An ESCA investigation of some copper complexes

Abstract A series of copper complexes have been investigated by ESCA. All complexes were salts of the tetraphenylphosphonium ion. The binding energies of all the atoms in the complexes were determined. From the binding energies of the ligand atoms we estimated the effective charges on these atoms. For this purpose we used linear relations of the form Eb = kq + EbO which had been established previously within our scheme of C 1s (phenyl) as internal standard. From the data thus obtained, the effective charge on the copper atom was estimated. A linear relation between binding energy and the effective charge on the copper atom was found, i.e., Eb(Cu) = 1.52qCu + 932.2 ESCA spectra were recorded for the complexes bis(1,3-diphenyl-1,3-propanediono) copper (II) and bis(3-phenyl-2,4-pentanediono) copper (II). By a combination of the XPS binding energies and IR intensities of the νCH vibrations of the phenyl groups in the complexes with empirical relations between these entities and the effective charges of the atoms and groups, a fairly complete mapping of the charge distributions of these complexes has been achieved.

A reinvestigation of the binding energy versus atomic charge relation for oxygen from X-ray photoelectron spectroscopy

Abstract An improved correlation between the binding energy of oxygen core electrons (Eb (Ols)) and the effective charge of the oxygen atom (qo) is proposed: Eb(01s) =4.23-qo +534.1.

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.

A relation between the atomic charge of carbon and the C1s core electron binding energy estimated from a comparison of gas phase and solid state data and the molar polarizabilities of the investigated molecules

Abstract A method for internal calibration of ESCA (XPS ) spectra is described that permits the use of a simple relation between binding energy (Eb) and atomic charge (q) : Eb = kq + Eb0. This relation has been shown to hold for a large number of elements. So far the relation for carbon has, however, not been very well established. A method is now described that allows the use of carbon charges determined from Eb, vs. q correlations for other elements and has also made it possible to establish a linear relation for carbon. The method does not use carbon charges determined directly from quantum chemical calculations. As an essential part of this procedure we investigated empirically the possible relation between the difference between the gas phase calibration standard and that for the same element in the solid state, “a”, and the molar polarizability of the substance, P. It was found that “a” decreases with increasing polarizability, tentatively as a=4.15+8.30 P− 1 3 . Therefore, knowledge of the polarizability of carbon-containing molecules from the literature made it possible to determine “a” and then the charge of all other atoms in the molecule. In this way a set of Eb and qc date was obtained. These data were complemented by another set using theoretical qc snd solid state Eb of phenyl compounds previously made. The results of the investigation show a linear relation between Eb(Cls) and qc valid for the solid state: Eb,(Cls) = 4.68 qc + 286.2 eV with a correlation coefficient of 0.945. This brings the previously obtained k value for carbon, which seemed anomalously high, down to a value of similar magnitude as for other light elements.

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.

A Correlation between Binding Energy and Atomic Charge for Oxygen from X-ray Photoelectron Spectroscopy Based on an Internal Standard for Calibration

Abstract X-ray photoelectron spectra (ESCA) for some compounds containing oxygen atoms have been measured. The Cls binding energy of the carbon atoms of phenyl groups has been used as an internal standard. The actual value of this binding energy has been determined from a previously found relation between Eb (Cls) and the infrared absorption intensity (ACH) of the C-H stretching vibrations of the phenyl group. In this way a correlation between the binding energy of the oxygen atom Eb (Ols) and its effective charge (q0) could be set up: Eb = 6.04. q + 535.6. The charges were quoted from quantum chemical calculations in literature or in some cases (e. g. triphenylphosphite and diphenylether) derived from a previously reported relation between the infrared absorption intensity (ACH) and total charge of the phenyl group in compounds of the type C6H5X.

On the kinetics of the oxidation of formic acid by vanadium(IV) in aqueous solution

Abstract The oxidation of formic acid by oxovanadium(IV) ions in sulphuric acid medium has been investigated spectrophotometrically. Platinum dispersed on titanium dioxide was used as a catalyst. The kinetics indicated a set of consecutive reactions, where the product of the first reaction, vanadium(III), was further reduced to vanadium(II) by formic acid. The rate constants were determined and a mechanism is proposed for the oxidation. The rate constants of both reactions were found to decrease with increasing hydrogen concentration.

An ESCA investigation of some dithiooxalato complexes

Abstract A series of dithiooxalato complex ions have been investigated as their tetraphenyl-phosphonium and potassium salts. Core-electron binding energies (Eb) of S, C, and O were determined, as well as those of the metals. From the first-mentioned data, effective charge values (q) were estimated for the atoms of the ligands. For this purpose linear relations (Eb = k · q + EbO) were used that had been previously derived within a scheme using C ls (phenyl) as the internal standard. From the data thus obtained the effective charge on the metal atoms could be estimated. The data is used to test if analogous linear relations also hold for the heavy elements; for example, we have found Eb(Pt) = 3.17 · qpt + 71.1 eV.

Oxidation of methanol, formaldehyde and formic acid by vanadium (IV) ions in sulphuric acid

Abstract The kinetics of the oxidation of methanol, formaldehyde and formic acid in sulphuric acid by vanadium(IV) ions have been followed spectrophotometrically. As catalyst a platinum/titanium dioxide system has been used. The methanol and formaldehyde reactions were hindered by the appearance of a slowly reacting intermediate on the catalyst surface. Contrary to this, the catalyst was only slightly affected when exposed to formic acid, and the oxidation reaction followed almost a first-order reaction. From the appearance of the kinetic curves in the first two cases it was possible to deduce the structure of the slowly reacting intermediate (HCOC), indicating that exactly 1.4 electrons per site are required for its complete oxidation.