Molecular structure of tris(acetylacetonato)scandium Sc(C5H7O2)3

Molecular structure of tris(acetylacetonato)scandium, Sc(C₅H₇O₂)₃, is investigated by gas-phase electron diffractometry. The main structural parameters of the molecule are evaluated. The average internuclear distances and angles correspond to C₃ symmetry. The chief structural motif is trigonal antiprisms of six oxygen, carbon, and hydrogen atoms with a scandium atom at the center. It is found that r_g(Sc-O) = 204.1(8) pm and r_g(C-O) = 124.7(4) pm. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 633–639, July–August, 1998.     

Formation of spatial spiral light structures by a polymer nanocylinder

The observation of spiral spatial structures of light formed by an unmetallized nanoobject is reported. It is shown experimentally that a single polymer nanocylinder is capable of forming single and double spirals in two-dimensional cross sections of the spatial intensity distribution of cw laser radiation in the space above the nanocylinder top.     

Ketene organoelement derivatives. Synthesis of bis(l-R-2-oxovinyl)silanes and germanes (R = SiMe3, GeMe3, SnMe3)

Earlier unknown 1,3-bisketene organoelement derivatives RMeE(C(E ’Me₃)=C=O)₂ (E = Si, Ge; E’ = Si, Ge, Sn) have been synthesized by the reaction of bis(alkoxyethynyl)silanes and -germanes with Me₃E’Hal. Bis(1-trimethylsilyl-2-oxovinyl)silane is also formed by the reaction of trimethylsilyl- and (dimethylsilylene)bisketenes with dimethylsilylene bistriflate and trimethylsilyl triflate, respectively. Addition of nucleophiles to the ketene fragment of compounds synthesized has been studied.     

Non-local symmetries of first-order equations

It is shown how one can transform scalar first-order ordinarydifferential equations which admit non-local symmetries of theexponential type to integrable equations admitting canonicalexponential non-local symmetries. As examples we invoke theAbel equation of the second kind, the Riccati equation and naturalgeneralizations of these. Moreover, our method describes howa double reduction of order for a second-order ordinary differentialequation which admits a two-dimensional Lie algebra of generatorsof point symmetries can be affected if the second-order equationis first reduced in order once by a symmetry which does notspan an ideal of the two-dimensional Lie algebra.     

Synthesis of amino-containing meso-aryl-substituted porphyrins and their conjugates with the closo-decaborate anion

Amphiphilic meso-aryl-substituted porphyrins containing an amino group and long-chain hydrophobic substituents were synthesized. Two strategies of the synthesis of asymmetric amino-containing porphyrins using p-acetamidobenzaldehyde and p-nitrobenzaldehyde were developed and investigated. A series of new substituted porphyrin-containing closo-decaborates were prepared based on the synthesized porphyrins and nitrilium derivatives of the closo-decaborate anion [B₁₀H₁₀]^2?.     

Preferential oxidation of carbon monoxide on supported gold catalysts

Catalyst precursors containing 1% Au were synthesized by the impregnation of Al₂O₃ and CeO₂-Al₂O₃ supports with an aqueous solution of HAuCl₄ followed by drying, treatment with aqueous ammonia for the removal of chlorine residues, and final drying at 90°C. The oxidation of CO in gas containing ～1 vol % O₂, ～1 vol % CO, 60 vol % H₂, and the balance N₂ on the activated catalysts was studied. In a number of experiments, to 18 vol % water was added to the gas mixture. The activation of precursors by the initial gas was studied. It was found that the prolonged storage of a precursor in air made its activation difficult to perform. The 1%Au/Al₂O₃ catalyst activated by the gas mixture stably operated in the preferential oxidation of CO at room temperature with the occurrence of the reaction in the mode of catalyst surface ignition (a hot spot at the bed inlet) under a change in the feed gas flow rate by a factor of 3. The effect of the presence of additional CO₂ (to 39 vol %) on the oxidation of H₂ was studied: the catalyst activity decreased. Because the reaction of CO₂ reduction to CO did not occur, the effect can be due to the adsorption of CO₂ on gold. The effect of the addition of water vapor to the feed gas was studied with the use of 1%Au/CeO₂-Al₂O₃ as an example. The exo/endo effects related to the adsorption/desorption of water on the catalyst surface were detected upon steam supply and shutoff at a bed temperature of 100–150°C. It was noted that the addition of water vapor to a certain level favorably affected the selectivity (decreased the residual concentration of CO). The boundary water concentration, at which the effect became negative, depended on catalyst bed temperature. The higher was the bed temperature, the greater amount of water could be added until the manifestation of a negative effect.     

On the distribution of the maximum of the difference of independent renewal processes with discrete time

We find the distribution of the maximum of the difference of two renewal processes with discrete time that is semicontinuous in discrete topology. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 10, pp. 1426–1432, October, 1998.     

Use of Equivalent Reactant Feeding in Deposition of Ni–Mn–O Coatings by Molecular Layering

Russian Journal of Applied Chemistry - The deposition of Ni–Mn–O thin films by molecular layering with equivalent feeding of organometallic reactants was studied....