STRUCTURE INVESTIGATION OF METAL COMPLEXES BY MEANS OF X-RAY EMISSION AND PHOTOELECTRON SPECTROSCOPY

The ability of the Ni Lα, β, S Kβ, O Kα, and Ni 2p spectra to distinguish between chemical states of atoms and their various environments is applied for structural characterization of nickel coordination compounds. In addition to the well documented influences of metal oxidation state and the electronegativity, the dependence of the energy shifts and intensity ratios upon the coordination geometry and the chelate ligand structure is discussed

Characterization of the mercaptobenzothiazole bonding on cadmiumsulfide by MO interpretation of NK XANES results

The X-ray absorption near-edge structures (XANES) at the nitrogen K-edge of mercaptobenzothiazole (MBT), its anion, a chelate complex of this molecule, and its adsorbate on CdS(10 (1) over bar0) exhibit distinct qualitative differences and characteristic peak shifts. It is shown that density functional theory (DFT) calculations of the respective systems in their electronic ground state can lead to an understanding of these spectral features. Their interpretation in terms of excitations into virtual molecular orbitals allows the assignment of the signals to functional groups in the chemical systems. By this means, the spectroscopic information on the adsorbate structure is confirmed and rationalized on a theoretical basis. It is deduced from the spectra that MBT is definitely adsorbed in its anionic form. (C) 2002 Elsevier Science B.V. All rights reserved

Splitting of the 1s−13p\mathrm{1s^{−1}3p} resonance at the sulfur atom in planar sulfur gold complexes

Results of experimental and theoretical investigation of X-ray absorption S K near edge structure in gold complex compounds with isomaleonitrildithiolate and isomaleonitrilthioselenolate ligands are presented. In the framework of a quasi-atomic model the splitting of the 1s−13p resonance at the sulfur atom has been found to dominate the S K XANES. Approximating the surrounding effect by fragments which include all sulfur and gold atoms a threefold splitting of the resonance was obtained. The components may be attributed to particular σ and π antibonding electronic states of the complex molecule. Comparing the results for both complexes the strong influence of the local structure on the resonance splitting is elucidated

Nitrogen K-shell excitations in complex molecules and polypyrrole

Experimental and theoretical studies of nitrogen K-shell near-edge absorption in complex compounds such as thiourea, benzalaniline, pyrrole, polypyrrole, tetraethylammonium, tetrabutylammonium and substituted 2-hydroxy-3-methoxy-benzyl-idene-aniline compounds were carried out. The quasi-atomic model was used in order to calculate the spectral distribution of oscillator strengths for transitions from the N 1s level to excited discrete and continuum states, to explain general trends in the changes of K-shell excitation spectra and to reveal their relationships with chemical bonding of the N atom in the compounds. The performed analysis of theoretical and experimental spectra evidences the central role of splitting of an intense N 1s−12p resonance in N K XANES formation in all compounds under study. The influence of the electronic charge transfer, bond conjugation and localization on the energies and intensities of π∗ and σ∗ resonances are discussed in detail. The strong connection between interference and chemical bonding effects on the main resonance features of X-ray absorption in the compounds under study is revealed