L. N. Mazalov

Thiacalix[4]arenes: Extraction of palladium and the electronic structure

The extractability of palladium nitro complexes with the charge state of sulfur and oxygen atoms in thiacalix[4]arenas in the cone and 1,3-alternate conformations are compared. The results of X-ray photoelectron and X-ray emission studies indicate the presence of considerable electron density on the bridging sulfur atoms, which is due to the contribution of the sulfur 3p AO to the upper occupied MOs of molecules. A series of changes in the electron density on sulfur atoms in the order calixarene thioethers > thiacalixarenes > dialkylsulfides ((C10H21)2S) > (C6H5)2S not completely coincide with changes in their extrability, which can be caused by different nature and stoichiometry of the formed palladium complexes.

Interpretation of X-ray photoelectron spectra of free nitroxyl radicals

N1s and O1s X-ray photoelectron spectra of stable nitroxyl radicals (substituted piperidine-1-oxyl, 2-imidazoline-1-oxyl, and 2-imidazoline-3-oxide-1-oxyl) and also diamagnetic derivatives with a {ONCNO} fragment are measured. It is shown that the structure of N1s and O1s X-ray photoelectron spectra of nitroxyls is determined by charge transfer processes between different parts of the molecule to screen the X-ray hole and the spin-spin interaction of unpaired electrons on the HOMO and 1s level.

XPS, XES, and quantum chemical investigation of the electronic structure of thiacalix[4]arenes and calix[4]arene thioesters

The X-ray photoelectron and X-ray emission spectra as well as the charge state of thiacalix[4]arenes in the cone and 1,3-alternate conformations and calix[4]arene thioesters were studied. The donor ability of sulfur bridging atoms in the studied compounds was shown to be close to that in dialkyl sulfides. The internal X-ray transitions (Kα and Kβ) were described by the energy of Kohn-Sham orbitals calculated by DFT method with relaxation corrections.

XPS spectra of free nitroxyl radicals and their electronic structure

The N(1s) and O(1s) XPS spectra of stable nitroxyl radicals and molecules with a related heterocycle structure: 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(3-nitrophenyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(2-hydroxyphenyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(2-hydroxy-3-nitrophenyl)-4,5-dihydro-1Himidazole-3-oxide-1-oxyl, and 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-3-oxide were studied. The possibility to apply X-ray electron spectra for investigation of the charge electron and spin density distribution on free radical atoms and at their coordination by a metal is considered.

X-ray emission study of the electronic structure of binuclear niobium complexes with (S 2 ) 2 –disulfide bridging ligands

The electronic structure of binuclear niobium complexes [Nb2S4(acac)4] and K4[Nb2S4(ox)4] is studied by X-ray emission fluorescent spectroscopy and quantum chemistry techniques. Data on the partial atomic composition of highest occupied molecular orbitals of the complexes are obtained. The energy positions of bonding and antibonding frontier molecular orbitals observed in the X-ray emission spectra of binuclear [Nb2((S2)2–)2]4+ clusters are determined by the analysis of overlap populations.

EFFECTS OF THE NEAREST-NEIGHBOR ENVIRONMENT OF COPPER ATOMS ON THE XANES SPECTRA OF LAYERED CHROMIUM-COPPER DISULFIDES

In the present work, the K absorption spectra of copper, chromium, and vanadium of layered chromiumcopper disulfides CuCr1–xVxS2 (x = 0–0.4) are studied. Based on the comparison of the experimental and theoretical spectra obtained by simulation with the FDMNES program package, it is shown that copper atoms occupy tetrahedral sites, and chromium atoms and substitutional vanadium atoms occupy octahedral sites in the whole set of the samples studied.

X-ray spectral and quantum chemical study of the electronic structure of thiacalix[4]-arenes and their acyclic analogs

An X-ray photoelectron and X-ray emission study of the charge state of thiacalix[4]arenes is performed with a comparison with the data of quantum chemical calculations. Relaxation corrections between the Kohn-Sham orbital energies calculated by the DFT method and experimental parameters of the X-ray emission and photoelectron spectra of the studied compounds are estimated. It is shown that the formation of a cyclic aromatic system in thiacalixarenes results in a decrease in the energy of orbitals involving p-π interactions of the bridging sulfur atoms and aromatic moieties, which determines the features of the X-ray emission spectra of the studied compounds.

XES investigation of the layered vanadium-substituted copper-chromium disulfides

XRD data on the layered vanadium-substituted copper-chromium disulfides (CuCr1−xVxS2, x = 0−0.4) are compared with the data obtained by X-ray emission and photoelectron spectroscopies.

X-ray photoelectron and X-ray emission study of the electronic structure of hexanuclear Mn(II,III) pivalate complexes

The electronic structure of hexanuclear Mn(II,III) pivalate complexes with tetrahydrofuran and isonicotinamide are studied by X-ray photoelectron spectroscopy and X-ray emission spectroscopy. It is shown that when isonicotinamide substitutes for tetrahydrofuran the spin state of manganese ions is retained; the electron density increases on the manganese and oxygen atoms of the [Mn6(O)2Piv10] core.

Electronic structure of calix[4]arene thioethers and their complexes with palladium, as studied by X-ray emission spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry

The charge state of calix[4]arene thioethers and their complexes with palladium was studied by X-ray emission spectroscopy and X-ray photoelectron spectroscopy. Experimental data were compared with the results of quantumchemical calculations. The involvement of the sulfur lone electron pairs in the coordination to Pd atoms causes a decrease in the energies of the corresponding MOs having contributions from the sulfur 3p AOs and, consequently, a decrease in the intensity of the maximum A on going from the S(Kβ) spectra of free ligands to the spectra of complexes. The binuclear nature of the complexes does not lead to the onset of significant additional interactions between two metal centers.