Higher order spin resonances in a 2.1-GeV/c polarized proton beam

Spin resonances can depolarize or spin flip a polarized beam. We studied 1st and higher order spin resonances with stored 2.1 GeV/c vertically polarized protons. The 1st order vertical (ν(y)) resonance caused almost full spin flip, while some higher order ν(y) resonances caused partial depolarization. The 1st order horizontal (ν(x)) resonance caused almost full depolarization, while some higher order ν(x) resonances again caused partial depolarization. Moreover, a 2nd order ν(x) resonance is about as strong as some 3rd order ν(x) resonances, while some 3rd order ν(y) resonances are much stronger than a 2nd order ν(y) resonance. One thought that ν(y) spin resonances are far stronger than ν(x), and that lower order resonances are stronger than higher order; the data do not support this.     

Crystal and molecular structures of ZnPhen(C2H5OCS2)2 and Zn(2,2′-Bipy)(n-C4H9OCS2)2 mixed-ligand coordination compounds

ZnPhen(EtOCS₂)₂ (I) and Zn(2,2′-Bipy)(n-BuOCS₂)₂ (II) mixed-ligand complexes have been synthesized. The structures were solved from X-ray diffraction data (CAD-4 and X8-APEX diffractometers, MoK _α radiation, 1879 and 3637 F _hkl , R = 0.0374 and 0.0315). Crystals I are monoclinic with parameters a = 11.678(3) Å, b = 19.215(3) Å, c = 9.655(1) Å; β = 101.23(1)°; V = 2125.0(7) ų; Z = 4, space group P2₁/c; crystals II are triclinic with parameters a = 8.7875(3) Å, b = 11.833(1) Å, c = 13.3454(6) Å; α = 112.154(2)°, β = 108.503(1)°, γ = 92.787(2)°; V = 1196.2(1) ų; Z = 2, space group 1 $P\bar 1$ . The structures are composed of discrete mononuclear molecules. The polyhedra of the Zn atoms are distorted trigonal bipyramids N₂S₃ formed by coordination of the N atoms of Phen or 2,2′-Bipy molecules and sulfur atoms of the monodentate and cyclic bidentate xanthogenate ligand. In structures I and II, dimer assemblies are formed by π-π interactions of Phen or 2,2′-Bipy molecules.     

A study of cryostructuring of polymer systems. 46. physicochemical properties and microstructure of poly(vinyl alcohol) cryogels formed from polymer solutions in mixtures of dimethyl sulfoxide with low-molecular-mass alcohols

Poly(vinyl alcohol) (PVA) cryogels (PVACGs) are obtained and studied. The PVACGs are formed by freezing–defrosting of polymer solutions in dimethyl sulfoxide (DMSO) or its mixtures with one of the first members of the series low-molecular-mass aliphatic alcohols (methanol, ethanol, n-propanol, and n-butanol). PVA content in these solutions is 100 g/L, while the concentration of an aliphatic alcohol is varied in a range of 0.44–2.55 mol/L depending on its nature. The polymer solutions are subjected to the cryogenic treatment at temperatures 30, 40, or 50°C lower than the crystallization temperature of DMSO (+18.4°C). The frozen samples are defrosted at a heating rate of 0.03°C/min. It is shown that, in a certain range of lowmolecular-mass alcohol content in an initial system, its cryogenic treatment yields coarse-pored heterophase cryogels that have higher rigidity and heat endurance than those of DMSO–PVA cryogels. It has been shown that polymer cryoconcentration and phase separation play important roles in the formation of a cellular microstructure and an increase in the rigidity and heat endurance of PVACGs obtained in the presence of low-molecular-mass alcohols.     

Textural characteristics of sulphided hydrotreatment catalysts prepared using Co–Mo complex compounds

Sulphided Co–Mo catalysts prepared by supporting (CoL)₂[Mo₄(C₆H₅O₇)₂O₁₁]·xH₂O on γ-Al₂O₃ were studied. Pores with diameters less than 40 Å in the catalysts preliminary dried at 120 °C were observed. The volume of these pores is proportional to the amount of carbon-containing decomposition products of the citrate ligands. No narrow pores in preliminary calcined catalysts were observed, whereas a sulphided active component was uniformly distributed in pores with diameters greater than 50 Å, independent of the active-metal concentration. The morphology of the active component particles depends on the conditions of the heat pretreatment. Catalysts that contain particles with an average of 2.1 ± 0.2 layers in a stack and pores with diameters of 60–120 Å are the most active in the hydrotreatment of diesel fuels.     

Water adsorption on tin hydrodioxide and its effect on the contour of the infrared absorption band ν(OH)

Tin hydrodioxide SnO₂ · nH₂O (THO, n = 1.5) pellets in potassium bromide were studied by IR absorption spectroscopy. Water adsorption by tin hydrodioxide was shown to give rise to a prominent strong and broad band of stretching vibrations ν(OH) with a peak at 3430 cm^?1. Absorption intensity of this band decreases with distance from the peak rapidly toward higher frequencies and very slowly toward lower frequencies; therefore, the contour is distinguished by very high asymmetry. Analysis of the reasons for this asymmetry taking into account the computer decomposition of the contour into components implies that the unresolved bands from two types of water molecules in THO are superimposed onto the weak bands from two types of hydroxide groups. First type molecules are involved in physisorption to form, with one another, hydrogen bonds that are similar to weak bonds in zeolite and liquid water. Second type molecules are involved in chemisorption and are coordinated to tin ions. Coordination enhances the strengthening of acidic properties and promotes the appearance of strong H-bonds. The peak intensity of the THO ν(OH) band depends primarily on the contribution of vibrational transitions of first type molecules and to a lesser extent on the contribution of vibrational transitions of the first type hydroxide groups. The vibrational transitions in second type molecules and second type groups influence the curvature of the contour on the low-frequency side of the peak.     

Features of high-temperature behavior in NdCaCoO<Subscript>4</Subscript>—the catalyst of the partial oxidation of methane to syngas

The peculiarities of the high-temperature (373–1173 K) behavior and transport properties of NdCaCoO₄, which is a highly active and selective catalyst of the partial oxidation of methane to syngas, were considered. A relationship between its thermal and electrophysical properties and the structure and defectiveness of the oxygen sublattice was found. The electric conductivity of this compound, which is a two-dimensional analog of perovskite, was found to be almost independent of the oxygen pressure (\(p_{O_2 } = 10^{ - 4} - 1\) atm) and to increase with temperature, reaching ～100 S/cm at 1173 K. The temperature dependence of the conductivity of the n-type semiconductor NdCaCoO₄ has two thermoactivation regions (373–573 and 573–873 K), in which the activation energy is almost doubled (0.46 and 0.81 eV, respectively). The discovered tendencies that determine the unique catalytic properties of this material are probably due to the change in the energy spectrum of this compound. The hypothetical reasons for this change are discussed.     

On justification of Cu(II) environment in mononuclear complexes: Joint X-ray and AIM studies

Interaction of copper(II) acetate with benzoic acid (benzene-1,3,5-tricarboxylic acid = H₃-btc and 3,5-dinitro-benzoic acid = H-dnb) and pyridine (Py) resulted in two mononuclear square-planar complexes with the compositions [Cu(H₂-btc)₂(Py)₂] (1) and [Cu(dnb)₂(Py)₂] (2). The recrystallization of 2 from dimethylsulfoxide (DMSO) yielded the square-bipyramidal complex [Cu(dnb)₂(DMSO)₂(H₂O)₂] (3). Crystal structures of 1-3 were determined by single crystal X-ray diffraction at 100 K. The square-planar Cu(II) geometry with the Cu-O and Cu-N distances of 1.924(2), 1.925(2) and 2.024(3) and 2.025(3) Å in 1, and 1.930(4) and 2.033(5) Å in 2 was found. The extended H-bonding system in 1 built on the robust carboxylic synthons is giving rise to the high-ordered porous layered structure. Insight into metal center environment and stabilizing intramolecular short interactions is obtained through quantum theory of atoms in molecules (QTAIM). As revealed by QTAIM, in octahedral complex 3 Cu-dnb and Cu-DMSO bonds are stronger than Cu-N bonds in 1 and 2.     

Highly diastereoselective four-component synthesis of polysubstituted 2-piperidinones with three and four stereogenic centers

Research on Chemical Intermediates - A novel four-component diastereoselective synthesis of polysubstituted 2-piperidinones is reported. The Michael addition–Mannich cascade of...