Synthesis of Structurally Varied 1,3‐Disiloxanediols and Their Activity as Anion‐Binding Catalysts

A series of new 1,3‐disiloxanediols has been synthesized, including naphthyl‐substituted and unsymmetrical siloxanes, and demonstrated as a new class of anion‐binding catalysts. In the absence of anions, diffusion‐ordered spectroscopy (DOSY) displays self‐association of 1,3‐disiloxanediols through hydrogen‐bonding interactions. Binding constants determined for 1,3‐disiloxanediol catalysts indicate strong hydrogen‐bonding and anion‐binding abilities with unsymmetrical siloxanes displaying different hydrogen‐bonding abilities for each silanol group.     

Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.     

Study on hydrogen sulfide plasma passivation of 790-nm laser diode cavity surface

In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes(LDs) by means of H2S plasma passivation technology,H2S plasma passivation treatment is performed on the GaAs(110) surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces axe treated under the optimum passivation conditions.Consequently,compared with unpassivated lasers with only AR/HR-coatings,the catastrophic optical damage (COD) threshold value of the passivated lasers by H2S plasma treatment is increased by 33%,which is almost the same as that of (NH4)2Sx treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH4)2Sx solution wet-passivated treatment.     

Quantitative Modelization of Hydrogen-Bonding in Polyoxometalate Chemistry

The PACHA (Partial Atomic Charges and Hardnesses Analysis) formalism is applied to polyoxometalate chemistry. Using the Ca₂(H₃O)₂[V₁₀O₂₈]16H₂O crystal structure, it was shown that the relative affinity for protons of the various oxygen sites may be quantitatively determined. The charge distribution was also found to be in good agreement with ¹⁷O and ⁵¹V NMR measurements. The H-bond energy in this kind of compound was found to be about –17 kJmol^–1, i.e., about 20% lower than in hexagonal ice. Finally, the 57 H-atom coordinates characterizing this structure were successfully recovered from a crystal structure optimization in the solid-state through electrostatic balance minimization. The importance of considering neutral clusters for a good modelization was demonstrated not only in the case of the decavanadate structure, but also in polysilicate chemistry. For the first time a clear picture emerges explaining the widespread occurrence of four- and five-membered rings in zeolite and silicate chemistry. The possibility of forming much larger polyanions with transition metal cations, is well explained using the crystal structure of the superfullerene keplerate [Mo₁₃₂O₃₇₂(HCO₂)₃₀(H₂O)₇₂]^42– as a benchmark compound. The possibility of performing an ab-initio retrosynthetic analysis of this cage is demonstrated.     

Hydrogen-Peroxide Epoxidation of Natural Olefins Catalyzed by a Dinuclear Manganese Complex

The complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L) [L₂Mn₂O₃](PF6)2 catalyzes epoxidation of (+)-limonene in CH₃CN solution at room temperature. Adding CH₃COOH accelerates the reaction. The products are isomers of limonene epoxide with predominance of that with an epoxified ring double bond. Epoxidation of - and -pinene by this system is less effective, apparently due to extensive steric shielding of the double bonds in the pinenes.     

Hydrothermal Synthesis of the Blue Potassium Molybdenum Bronze, K0.28MoO3

Blue potassium molybdenum bronze, K_0.28MoO₃, was prepared by hydrothermal heating hydrogen molybdenum bronze in KCl solution at 431 K. Hydrated molybdenum bronze was found formed as an intermediate during the conversion from hydrogen molybdenum bronze to blue bronze. The hydrothermal method proved itself an easy and effective for synthesis of mixed-valence compounds.     

Unusual Behavior of Nanocrystalline Strontium Oxide Toward Hydrogen Sulfide

The thermodynamically favored reaction of solid strontium oxide with gaseous hydrogen sulfide is kinetically enhanced to a large degree by the use of higher surface area nanocrystalline SrO in the form of brush-like collections of metal oxide fibers. An unusual feature is that the reaction SrO + H₂S SrS + H₂O proceeds stoichiometrically at room temperature, but at higher temperatures the reaction efficiency goes down, apparently due to rapid temperature induced crystal growth of the nanocrystalline SrO. The samples studied vary in crystallite size from 20 to 27nm, while average particle size (nanocrystal aggregates) varies in the following order; aerogel prepared SrO (100nm) 相似文献   

Solution calorimetry of organic nonelectrolytes as a tool for investigation of intermolecular interactions

The paper is mainly the review and generalization of the previous publications of the authors. It demonstrates that solution calorimetry method gives the opportunities of more detailed understanding of various aspects of intermolecular interactions in solution. We are assured that prerequisite to such an understanding is the successive analysis of various solute–solvent systems from the simplest ones which include alkanes as a solute or as a solvent to the most complex systems with solvent self‐association via hydrogen bonding. Particular findings discussed in this paper are (i) an inconspicuous contribution of electrostatic solute–solvent interaction to the solvation enthalpy and, accordingly, the dominating contribution of dispersion interactions for nonspecifically solvated solutes; (ii) new, very general method for the extraction of specific interaction enthalpy from the enthalpy of solvation; (iii) new method of determination of self‐association enthalpies for the solvents associated via hydrogen bonding; (iv) new method for determination of cooperative hydrogen bonding enthalpies of proton acceptors with associated species of alcohols; (v) the unique method of experimental determination of the hydrophobic effect enthalpy. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparison of solubility of gases and vapours in wet and dry alcohols,especially octan‐1‐ol

Equations for the solubility of gases and vapours into dry alcohols from methanol to decan‐1‐ol and into water‐saturated alcohols from butan‐1‐ol to decan‐1‐ol have been compared through the use of the Abraham solvation equation. It is shown that there are noticeable differences in solvation into the dry and wet alcohols, and that these differences become larger as the alcohols become smaller and take up more water. The two main factors that lead to the differences in solvation are the solute hydrogen‐bond basicity, B, and solute size, L. Increase in solute hydrogen‐bond basicity favours the wet alcohols and increase in solute size favours the dry alcohols. Solute hydrogen‐bond acidity plays no part, because the hydrogen‐bond basicity of water, wet alcohols and dry alcohols is almost the same. Copyright © 2008 John Wiley & Sons, Ltd.     

4-(1,4-Dimethoxy-2-naphthyl)-4- hydroxycyclohexanone and its ethylene ketal

Intramolecular hydrogen bonding in the solid state is reported for the title compound and its ethylene ketal. The title compound crystallizes in the triclinic space group, with a = 9.590(3), b = 9.620(3), c = 9.844(2) Å, = 97.67(2), = 105.25(2), = 115.47(2), and Z=2. The ethylene ketal crystallizes in the monoclinic space group, P2₁/c, with a = 7.230(2), b = 22.639(3), c = 10.839(2) Å, = 101.47(2), and Z = 4. The intramolecular hydrogen bond length of 1.79 Å is the same for the ketone and ketal, but the O—H---O valence angle is 144° for the ketone and 165° for the ketal.