Investigation of electron interaction in adsorption by static skin effect method

The reflection of the conduction electrons from surfaces of a thin (d = 100 μm) monocrystalline plate of tungsten [(110) face] is investigated by the method of static skin effect. It is found that by heating the crystal in vacuum up to 2500 °K, the oxide layer is removed and the specular reflection of the conductive electrons increases. The adsorption of the monomolecular layers of barium and copper atoms markedly increases diffuse reflection. A resonance mechanism of carrier interaction in the metal with adsorbed atoms is discussed.     

Use of imaging plates (IPs) in the gas-phase electron diffraction (GED) experiments on the EG-100 M apparatus. The tetrachloromethane molecule as a test object

The gas-phase electron diffraction (GED) experiment at the Moscow State University was carried out for the first time using imaging plates (IPs). The response of the Fuji BAS-MP IPs calibrated by means of ¹⁴C standard sources was found to be linear in a broad dynamic interval (larger than 10⁴). The GED study of tetrachloromethane was carried out in order to test the applied technique (IP reader FLA7000) and the developed software. The determined structural parameters of the CCl₄ molecule are in excellent agreement with those obtained in experiments with photographic registration.     

Tritium planigraphy and nanosized biological particles

Advances in studies of protein and complex biological systems by tritium planigraphy are considered. Particular attention is paid to detailing the structural organization of the protein components of the influenza virus. The structure of the M1 protein in a solution, virion, and crystal is analyzed. The specific features of this protein identified using tritium planigraphy and computer simulation are indicative of significant changes in its conformation depending on the “phase” state. Models of the spatial structure of the M1 protein in solution and in the virion are proposed. Structural disorder is observed in one of the three domains of this protein. Ideas on the importance of this structure for the multifunctional properties of the protein, such as binding to the membrane and a ribonucleoprotein complex, as well as the transfer of genetic material during viral infection of healthy cells, were suggested.     

Conformational composition of meta- and ortho-fluoro(trifluoromethoxy)benzene as studied by vibrational spectroscopy

The IR spectra of o- and m-F-C₆H₄OCF₃ in the gas, liquid, and solid (glass and crystal) phases were analyzed along with the Raman spectra of these compounds in the liquid and solid (glass and crystal) phases. This investigation includes both experimental and theoretical studies of the spectra. Vibrational frequencies and normal modes for all possible stable conformers of m- and o-fluoro(trifluoromethoxy)benzene were calculated using B3LYP/cc-pVTZ harmonic quantum-chemical force fields. It was found that m-F-C₆H₄OCF₃ exists as a mixture of the orthogonal and two planar conformers in the gas, liquid, and amorphous solid (glass) phases and as one orthogonal conformer in the crystal state, while o-F-C₆H₄OCF₃ exhibits only one orthogonal conformer in every phase.     

Disulphides of dithiophosphinic acids as analytical reagents-I Extractive spectrophotometric determination of palladium with some bis(dialkylthiophosphoryl)- and bis(diarylthiophosphoryl)disulphides

The disulphides of dithiophosphinic acids (DS) with the general formula R(2)P(S)SSP(S)R(2), where R = C(2)H(5), C(3)H(7), C(5)H(11), C(6)H(5) (I-IV) form coloured complexes of 1:3 stoichiometry with Pd(II). The absorption maxima and molar absorptivities are: a lambda(I) = 302 nm, epsilon(I) = 2.04 x 10(4) 1.mole(-1).cm(-1); lambda(II) = 305 nm, epsilon(II) = 2.58 x 10(4); lambda(III) = 303 nm, epsilon(III) = 2.60 x 10(4); lambda(IV) = 315 nm, epsilon(IV) = 3.25 x 10(4). The reaction takes about 3 min at room temperature, and the colour is stable for 24 hr. The influence of time, pH, reagent concentration, organic solvents and interferences have been studied. An extractive photometric method of determination of Pd(II) is described and applied to the determination of Pd(II) in a mixture of platinum metals.     

Molecular structure and conformation of nitrobenzene reinvestigated by combined analysis of gas-phase electron diffraction,rotational constants,and theoretical calculations

The molecular structure and conformation of nitrobenzene has been reinvestigated by gas-phase electron diffraction (GED), combined analysis of GED and microwave (MW) spectroscopic data, and quantum chemical calculations. The equilibrium r _e structure of nitrobenzene was determined by a joint analysis of the GED data and rotational constants taken from the literature. The necessary anharmonic vibrational corrections to the internuclear distances (r _e ? r _a) and to rotational constants (B _e ⁽ⁱ⁾  ? B ₀ ⁽ⁱ⁾ ) were calculated from the B3LYP/cc-pVTZ quadratic and cubic force fields. A combined analysis of GED and MW data led to following structural parameters (r _e) of planar nitrobenzene (the total estimated uncertainties are in parentheses): r(C–C)_av = 1.391(3) Å, r(C–N) = 1.468(4) Å, r(N–O) = 1.223(2) Å, r(C–H)_av = 1.071(3) Å, \({\angle}\)C2–C1–C6 = 123.5(6)°, \({\angle}\)C1–C2–C3 = 117.8(3)°, \({\angle}\)C2–C3–C4 = 120.3(3)°, \({\angle}\)C3–C4–C5 = 120.5(6)°, \({\angle}\)C–C–N = 118.2(3)°, \({\angle}\)C–N–O = 117.9(2)°, \({\angle}\)O–N–O = 124.2(4)°, \({\angle}\)(C–C–H)_av = 120.6(20)°. These structural parameters reproduce the experimental B ₀ ⁽ⁱ⁾ values within 0.05 MHz. The experimental results are in good agreement with the theoretical calculations. The barrier height to internal rotation of nitro group, 4.1±1.0 kcal/mol, was estimated from the GED analysis using a dynamic model. The equilibrium structure was also calculated using the experimental rotational constants for nitrobenzene isotopomers and theoretical rotation–vibration interaction constants.     

Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

Reaction of [Pd(PPh(3))(4)] with 1,1-dichloro-2,3-diarylcyclopropenes gives complexes of the type cis-[PdCl(2)(PPh(3))(C(3)(Ar)(2))] (Ar = Ph 5, Mes 6). Reaction of [Pd(dba)(2)] with 1,1-dichloro-2,3-diarylcyclopropenes in benzene gave the corresponding binuclear palladium complexes trans-[PdCl(2)(C(3)(Ar)(2))](2) (Ar = Ph 7, p-(OMe)C(6)H(4)8, p-(F)C(6)H(4)9). Alternatively, when the reactions were performed in acetonitrile, the complexes trans-[PdCl(2)(NCMe)(C(3)(Ar)(2))] (Ar = Ph 10, p-(OMe)C(6)H(4)11 and p-(F)C(6)H(4)) 12) were isolated. Addition of phosphine ligands to the binuclear palladium complex 7 or acetonitrile adducts 11 and 12 gave complexes of the type cis-[PdCl(2)(PR(3))(C(3)(Ar)(2))] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C(6)H(4), R = Ph 14, Ar = p-(F)C(6)H(4), R = Ph 15). Crystal structures of complexes 6·3.25CHCl(3), 10, 11·H(2)O and 12-15 are reported. DFT calculations of complexes 10-12 indicate the barrier to rotation about the carbene-palladium bond is very low, suggesting limited double bond character in these species. Complexes 5-9 were tested for catalytic activity in C-C coupling (Mizoroki-Heck, Suzuki-Miyaura and, for the first time, Stille reactions) and C-N coupling (Buchwald-Hartwig amination) showing excellent conversion with moderate to high selectivity.