ELECTRONIC STRUCTURE AND CHEMICAL BOND IN 9,9,10,10-TETRAETHYNYL-9,10- DIHYDRODISILAANTHRACENE

Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory....     

Electrodynamic properties of nanoporous silicon in the range from terahertz to infrared frequencies

The dielectric response (conductivity and permittivity) spectra of a series of nanoporous silicon samples prepared by anodization of low-resistivity single-crystal silicon are measured, for the first time, using terahertz and IR spectroscopy in the frequency range 7–4000 cm^?1 at room temperature. The spectra obtained are analyzed in terms of the effective medium theory with a size-dependent dielectric response function of nanoinclusions and averaged dielectric characteristics of the surrounding medium. The geometric and dielectric characteristics of silicon nanoinclusions are determined. The dielectric properties of inclusions are found to be affected by nanosize effects, namely, carrier scattering at crystallite boundaries and a broadening of the band gap due to quantum confinement. The spectra of the samples prepared by adding iodine to the electrolyte exhibit a resonance at frequencies of 150–300 cm^?1. The nature of the resonance can be associated with the presence of chemisorbed iodine on the surface of porous silicon. Possible mechanisms responsible for the changes in broadband conductivity and permittivity spectra of single-crystal silicon upon transformation into a nanoporous structure are discussed.     

The influence of glass coating on the single domain wall potential in amorphous glass-coated Fe-based microwires

The effect of the glass coating on the single domain wall potential in amorphous glass-coated Fe-based microwire has been studied by the switching field distribution technique. The thermoactivated mechanism model is used to describe the thermally activated switching through the complex energy barrier in amorphous FeSiB microwires. Glass removal leads to the increase of the probability of the thermally activated switching pointing to the decrease of the energy barrier.     

Asymptotics of solutions of a system of linear inhomogeneous singularly perturbed differential equations

Solutions with asymptotics in integral and fractional powers of the parameter ? are constructed for the vector differential equation $$\varepsilon ^h \dot X = A(t,\varepsilon ) X + \varepsilon ^{\alpha _1 } p(t,\varepsilon ) \exp \left( {\varepsilon ^{ - h} \int\limits_0^t {\lambda (\tau )d\tau } } \right)$$ in the case of resonance and multiple spectrum of the limit matrix. $$\varepsilon ^h \dot X = A(t,\varepsilon ) X + \varepsilon ^{\alpha _1 } p(t,\varepsilon ) \exp \left( {\varepsilon ^{ - h} \int\limits_0^t {\lambda (\tau )d\tau } } \right)$$      

Adsorption studies of organosubstituted laminated silicates

The hysteresis of sorptive deformation of sorbents has been studied for the first time. Based on the results obtained, it is assumed that the deformation of sorbents could be the universal reason for the sorptive hysteresis.For Part 1, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1477–1479, August, 1995.     

Interaction of Water and Methanol Molecules with the Surface of Carbonaceous Materials According to Gas Chromatographic Data

We have used gas chromatography to study the interaction of water and methanol molecules with active hydrophilic centers on the surface of thermally expanded graphite and graphitized thermal carbon black. We have determined the concentration of carboxyl and phenol hydroxyl groups on the surface of the sorbents and the heats of adsorption for adsorption of the studied substances on these groups. We have shown that water molecules are adsorbed as clusters on the hydrophilic centers of the studied sorbents at very low relative pressures, with n = 2 molecules in the cluster.     

Gas-Chromatographic Studies of the Interaction between Water and Methanol Molecules and the Surface of Carbon Materials

The gas-chromatographic method is used to study the interaction of water and methanol molecules with active hydrophilic centres existing at the surface of thermally exfoliated graphite and graphitized thermal carbon black. The concentration of carboxyl and phenol hydroxyl groups at the surface of these sorbents is determined, and heats of adsorption of the studied molecules are shown to be and 28−25 kJ/mol, respectively. It is also shown that adsorption of water at the hydrophilic centres at lowest relative pressure values takes place with formation of clusters consisting of n = 2 water molecules.     

The first tetranuclear vanadium(V) peroxo complex: Preparation, vibrational spectra and X-ray crystal structure of K6[V4O4(O2)8(PO4)]·9H2O

The vanadium(V) peroxo phosphato complex K₇[V₄O₄(O₂)₈(PO₄)]·9H₂O has been obtained from the KVO₃---KH₂PO₄---KOH---H₂O₂---H₂O---C₂H₅OH system. The X-ray structural analysis revealed a tetranuclear anionic structure in which two dinuclear [V₂O₂(O)₂)₂(μ-η¹ : η²-O₂)₂] units are connected by the μ₄-PO₄ group.     

Fused polycyclic nitrogen-containing heterocycles

The condensation of methyl phenylchloropyruvate with 1-phenyl-3-(2-pyridyl)thiourea and its 3-and 4-picolyl homologs affords the corresponding 4-hydroxythiazolidines, which react with o-phenylenediamine to give one of two possible thiazolo[3,4-a]quinoxalines containing the pyridyl-or picolylimine substituents at position 1. 3a-Hydroxy-3-phenylimino-1-(2-pyridyl)thiazolo[3,4-a]quinoxalin-4-(3H,5H)-one, which is a covalent hydrate of the final product, was isolated as an intermediate in this reaction.