Reaction of the [B<Subscript>10</Subscript>H<Subscript>9</Subscript>O<Subscript>2</Subscript>C<Subscript>4</Subscript>H<Subscript>8</Subscript>]<Superscript>–</Superscript> anion with C-nucleophiles

The reactions of 1,4-dioxane-substituted closo-decaborate anion ([B₁₀H₉O₂C₄H₈]^–) with metal acetylenides, diethyl malonate, ethyl acetoacetate, triethyl orthoformate, acetylacetone, and malonodinitrile were studied. The reactions were shown to be accompanied with substituent ring opening and attachment of the corresponding pendant functional group. The obtained compounds were characterized by various physicochemical methods (IR and polynuclear NMR spectroscopy, ESI mass spectrometry).     

The quantum-chemical estimation of the effect of phosphorus atoms on the electron acceptor properties of aluminum- and boron-containing zeolite clusters

The effect of a phosphorus atom introduced in a zeolite cluster involving ten silicon and aluminum atoms on the state of active catalytic structure sites is estimated. Zeolite clusters modified with boron are also considered. The effect of the electron density redistribution upon zeolite modification with boron and phosphorus, as well as the effect upon the coordination of probe water and ammonia molecules to the clusters, is analyzed. The bond energies of water or ammonia molecules coordinated to acceptor sites of phosphorus-containing zeolites are estimated. Experimentally discovered changes in the acidic properties of zeolites resulting from their modification with boron and phosphorus are interpreted.     

Chlorination of Sulfonium Derivatives of closo-Decaborate Anion with Carboxyl-Containing Substituents

Doklady Chemistry - The reaction of sulfonium closo-decaborate derivatives containing carboxyl groups with sulfuryl chloride SO2Cl2 as a halogenating agent was studied. The reaction gave fully...     

The effect of silicon-substrate orientation on the local piezoelectric characteristics of LiNbO<Subscript>3</Subscript> films

The domain structure of lithium-niobate thin films grown on Si(111) and Si(100) substrates coated with a native oxide layer with a thickness of no less than 2 nm is investigated by X-ray diffraction, scanning electron microscopy and piezoresponse force microscopy. The films are synthesized by the rf magnetron sputtering of a single-crystal lithium-niobate target. A high degree of grain orientation in the polycrystalline films is demonstrated. The piezoelectric coefficients d _zz of the lithium-niobate films on Si(111) and Si(100) substrates are calculated from the measured dependences of the amplitude of the piezoresponse signal on the ac voltage applied between the cantilever tip and the substrate. Piezoelectric hysteresis loops are obtained in the remanent piezoelectric response regime     

Lewis acid sites in boralites

This work is aimed at modeling a framework L-site of a boralite using DFT and a cyclic cluster including one B and two Si atoms. A similar cluster was used earlier as a successful model for an L-site of a zeolite, which allows for the direct comparison of the properties of the two L-sites. It is shown that the boralitic L-site is rather weak. Unlike its zeolitic counterpart, it cannot bind a molecule of ethene or carbon monoxide. Only a base as strong as ammonia can form a stable 1:1 complex with the boralitic L-site. Water is found to bind to the boralitic L-site only if not less than two of its molecules are interacting with the model cluster. As water loading increases, the geometry of the BO₃ fragment undergoes gradual changes indicative of facile hydrolysis of the boralite lattice.     

Simple molecules on a zeolite acceptor center: A quantum-chemical approach

The effectiveness and reliability of the cluster approach to modeling the interaction of several simple molecules (CO, water, ammonia, ethylene, and methanol) with zeolite acceptor centers was shown on the basis of various quantum-chemical methods and a comparison with the data of direct measurements. The Al···CO bonds were found to form in the complex of CO with three-coordinate aluminum. This allows the CO molecule to be used as a test for the acceptor properties of zeolites. A comparison of the calculation results and experimental data on the interaction of one to three RH-type molecules with a zeolite fragment led us to conclude that water, ammonia, ethylene, and methanol acquired proton-donor properties in the field of zeolite acceptor centers. These properties were similar to those of bridge OH groups in hydrogen zeolite forms. Probable schemes of catalysis on zeolites should be constructed taking into account the possible participation of acceptor centers in the conversions of molecules of the type specified.     

Adaptive X-Ray Optical Elements Based on Bending Piezoactuators: Possibilities and Prospects of Practical Application

Crystallography Reports - The possibilities of a new class of adaptive X-ray optical elements based on bending piezoelectric actuators for practical implementation of time-resolved experiments...     

Quantum-mechanical simulation of the interaction of aluminum- and boron-containing zeolite clusters with molecules of water and ammonia

Quantum-mechanical computations of zeolite clusters with molecules of water and ammonia have been carried out. The clusters consisted of ten atoms of silicon and aluminum, where one atom of aluminum was also replaced with an atom of boron. Values of the bond length and bond angles have been obtained; the geometry of adsorption complexes and the bond energy for molecules of water and ammonia with atoms of aluminum and boron of a zeolite fragment have been determined. The computed values of bond energy for molecule probes yield the quantitative strength characteristic of zeolite aprotic acid centers.