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Kuz'Micheva G.M.,Lomonosov Moscow University of Fine Chemical Technology | Ivleva L.I.,RAS A.M. Prokhorov General Physics Institute | Kaurova I.A.,Moscow State University | Rybakov V.B.,Moscow State University
Acta Materialia

Crystals of strontium barium niobate solid solutions, both nominally pure Sr0.61Ba0.39Nb2O6 and doped with transition metal (Cr3+ and Ni3+) ions, have been investigated by X-ray diffraction. The chemical composition of the undoped crystal was determined taking into consideration vacancies in niobium Nb(2) and oxygen sites and the statistical distribution of strontium in two (Sr(1) and Sr(2)) sites in the tetragonal tungsten bronze type crystal structure. It was established that the introduction of chromium or nickel oxides into the melt initial composition greatly influences the strontium and barium content in the crystals obtained and the distribution of these species in the crystallographic structure. The probability of finding the transition metal ions in regular and interstitial positions depending on their concentration and valence state is discussed. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Avakyan V.G.,Russian Academy of Sciences | Shapiro B.I.,Lomonosov Moscow University of Fine Chemical Technology | Alfimov M.V.,Russian Academy of Sciences
Dyes and Pigments

Quantum-chemical calculations for monomers, dimers, and tetramers of 3-ethyl-2-[(1E,3E)-3-(3-ethyl-1,3-thiazol-2(3H)-ylidene)prop-1-en-1-yl]-1, 3-thiazol-3-ium chloride and 3-ethyl-2-[(E)-(3-ethyl-1,3-benzothiazol-2(3H)- ylidene)methyl]-1,3-benzothiazol-3-ium chloride were performed. Both dyes were found capable of forming two kinds of π-stacking-dimers with various degree of overlap. Three kinds of tetramers: four-deck ladder, three-deck brickwork, and two-deck linear, can be formed without destruction of the dimers of the cyanine dyes. The energy of tetramer formation was found to decrease in the order brickwork > linear > ladder configurations. For dimers of the first dye and its tetramer (brickwork, ladder and linear) configurations, the energies of the first S0 → S1 singlet transitions, oscillator strengths, and structures of frontier MO have been calculated. The spectral shifts in dimers and tetramers were found to depend only on mutual orientation of components: brickwork and linear tetramers show red shift (+Δλ) while ladder tetramers, blue shift (-Δλ) of absorption bands (with respect to monomer). © 2014 Elsevier Ltd. All rights reserved. Source

Pestryakov A.N.,Tomsk Polytechnic University | Lunin V.V.,Moscow State University | Bogdanchikova N.,National Autonomous University of Mexico | Temkin O.N.,Lomonosov Moscow University of Fine Chemical Technology | Smolentseva E.,National Autonomous University of Mexico

(Graph Presented) Role of small and big gold particles in CO oxidation and methanol selective oxidation to formaldehyde has been studied by the methods of diffuse reflectance electron spectroscopy, XRD, XPS, HRTEM and catalytic testing. By comparison of catalytic and spectroscopic data it was concluded that states Auδ+ with certain effective charge (δ < 1) are active sites in low-temperature CO oxidation as well as in alcohol partial oxidation. These states can be formed under the action of different factors, such as metal-support interaction, redox treatments, and modifying additives. Modifiers stabilizing the ionic states of gold (Ce and Zr oxides) increase the selectivity of the catalyst in alcohol partial oxidation, whereas electron-releasing additions (La and Cs oxides) impair the catalyst properties. © 2012 Elsevier Ltd. All rights reserved. Source

Temkin O.N.,Lomonosov Moscow University of Fine Chemical Technology
Kinetics and Catalysis

The state-of-the-art in the theory of routes for multi-route reactions in the homogeneous catalysis with metal complexes is reviewed. Key problems and the possible approaches to their solution based on the Horiuti-Temkin theory of steady-state reactions, which are useful in constructing the kinetic algebraic mod- els of multi-route processes, are discussed. A classification of the mechanisms of real processes involved in the homogeneous catalysis with metal complexes is presented. The chain mechanisms of catalytic processes, conjugated and associated reactions, and critical phenomena in the dynamics of homogeneous reactions are considered. © Pleiades Publishing, Ltd., 2012. Source

Temkin O.N.,Lomonosov Moscow University of Fine Chemical Technology
Kinetics and Catalysis

Three possible mechanisms of the direct hydration of α-olefins under conditions of catalysis with metal complexes in solution are considered, and information that confirms the possible realization of the reaction steps of various types is presented. Factors determining the regioselectivity of reaction steps are considered in the framework of various mechanisms, and the available published data about catalytic systems capable of ensuring the direct hydration of α-olefins are analyzed. New approaches to organization of the synthesis of n-alcohols from olefins and dienes are discussed, which are based on the systems of consecutive reactions, conjugated, and combined (associated) processes. © 2014 Pleiades Publishing, Ltd. Source

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