Studying the coordination geometry of 3d transition-metal ions in complexes of crown-substituted porphyrins by EXAFS spectroscopy with allowance for multiple scattering

The structure of a series of complexes of 3d metals (Co, Ni, and Cu) with substituted porphyrins is studied by X-ray EXAFS spectroscopy. Together with complexes based on tetraphenylporphyrin and octaethylporphyrin with known crystalline structures, new complexes of asymmetrically substituted tetraphenylporphyrin, 5-(4-(((4′-hydroxy-benzo-15-crown-5)-5′-yl)diazo)phenyl)-10,15,20-triphenylporphyrin, are studied. Based on an analysis of experimental spectra with allowance for the contributions of multiple scattering, the coordination parameters of metal atoms at the center of the porphyrin ring are determined: the bond distances and valence angles between them for the first four coordination spheres around metal atoms. The EXAFS spectra are shown to be sensitive to the angular parameters. Differences in the geometric parameters in the series of studied metal-porphyrin complexes are analyzed.     

Cocatalytic effect of palladium and zinc in the condensation of alcohol carbon backbones into hydrocarbons

The results of the direct conversion of ethanol and its mixture with glycerol into a C₄–C₁₀₊ alkane and olefin fraction in the presence of Pd-, Zn-, and Pd-Zn-containing catalysts, which were prepared by supporting homo- and heterometallic acetate complexes onto the surface of γ-Al₂O₃, are reported. It was found that, in the presence of mono- and bicomponent Pd-ZnO (Pd; ZnO)/γ-Al₂O₃ systems, selectivity in the formation of alkanes, olefins, or their mixtures in the target fraction can be controlled as a result of the cocatalytic effect of active components that are responsible for the catalyst activity in condensation and hydrogenation reactions. The structures of the active components were studied and the genesis of the catalytic systems was characterized using XAFS, XPS, and XRD analysis. It was found that the addition of glycerol considerably increased the yield of the target hydrocarbon fraction.     

Magnetooptics and magnetic ordering in ferrite nanoparticles in glass doped with iron and rare-earth elements

Magnetic circular dichroism and X-ray diffraction were used to investigate the structure and magnetooptical properties of nanoparticles formed in potassium-aluminum-germanium-boron glass doped with iron and rare-earth elements. It is demonstrated that in thermally processed glass, the main magnetic phase of the formed nanoparticles is γ-Fe₂O₃ maghemite.     

Synthesis,Structural, and Physico-Chemical Study of Transition Metal Complexes with Schiff Base: A Product of Condensation of 2- N -Tosylaminobenzaldehyde and Tryptamine

A new Schiff base, the product of 2-N-tosylaminobenzaldehyde and tryptamine condensation, was synthesized and investigated. A physicochemical study and quantum chemical simulation of the azomethinee tautomerism were performed. Its complexes with Zn(II), Cu(II), Ni(II), Co(II), and Fe(III) were synthesized and studied.     

Cluster approach to the synthesis of ternary metal sulfides: Molybdenum disulfide single layers as a precursor

The reactivity of negatively charged (MoS₂) ^x? layers in aqueous single-layer dispersions resembles that of molecular Mo-S cluster compounds. These layers form covalent bonds with metal (M) cations (M=Cu, Ag, Pb, Cd, Hg, Pd), giving rise to ternary metal sulfides M _zMoS₂ whose Mo network contains direct Mo-Mo bonds.     

Study of the physicochemical properties and film structure of ternary graft copolymers of aromatic polyimide, ɛ-caprolactam,and ω-dodecanelactam

The microstructure of films of ternary graft copolymers of aromatic polyimide, ?-caprolactam, and ω-dodecanelactam has been studied by atomic force microscopy. It is shown that an increase in the content of ω-dodecanelactam units in copolymers leads to an increase in the diameter of spherulites composed of fibrils. Simultaneously, water absorption decreases and the mechanical properties and crystallinity of copolymer films change.     

Ultrafast core-hole-induced dynamics in water probed by x-ray emission spectroscopy

The isotope effect and excitation-energy dependence have been measured in the oxygen K-edge x-ray emission spectrum (XES). The use of XES to monitor core decay processes provides information about molecular dynamics (MD) on an ultrafast time scale through the O1s lifetime of a few femtoseconds. Different nuclear masses give rise to differences in the dynamics and the observed isotope effect in XES is direct evidence of the importance of such processes. MD simulations show that even the excitation-energy dependence in the XES is mainly related to differences in core-excited-state dynamics.     

Laser-electron x-ray generator

The possibility of developing a laser-electron x-ray generator based on the Thomson scattering of laser radiation by relativistic electrons and prospects for its application are considered. In its specifications (brightness, average intensity, and dimensions), as well as its construction and operation cost, such a generator is intermediate between x-ray tubes and synchrotron sources. The configuration of channels and experimental stations intended for applications of an x-ray laser-electron generator in studies of the elemental composition and structure of materials is discussed.     

Binuclear metallochelates of 2-(N-tosylamino)benzal-2’-(hydroxymethyl)aniline: Syntheses,structures, and magnetic properties

Binuclear complexes of Co(II), Сu(II), and Pd(II) with 2-(N-tosylamino)benzal-2’-(hydroxymethyl)aniline are synthesized. The compositions and structures of the ligand and complexes are determined from the data of elemental analysis, IR spectroscopy, ¹Н, ¹³С, and ¹⁵N NMR spectroscopy, X-ray absorption spectroscopy, and magnetochemical measurements in a temperature range of 294–77.4 K. All complexes are dimeric. The Cu…Cu and Cо…Cо distances equal to 3.03 and 2.99 Å, respectively, are obtained for the Cu(II) and Co(II) complexes. These complexes are characterized by the antiferromagnetic exchange interaction with 2J = –630 and –42 cm^–1, respectively.     

X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure study of water adsorption on pyridine-terminated thiolate self-assembled monolayers

Adsorption of water on self-assembled monolayers (SAMs) of 4-(4-mercaptophenyl)pyridine on gold at low temperatures under ultrahigh vacuum conditions is studied by synchrotron radiation X-ray photoelectron and absorption spectroscopy. Water adsorption induces a strong modification of the chemical state of the pyridine N atoms at the SAM/ice interface, indicative for strong H bonding and partial proton transfer between water molecules and pyridine moieties. Additionally, the initial molecular orientation within the SAM is changed upon formation of an adsorbed water multilayer.