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  • Computational Chemistry and Molecular Modeling  (1)
  • General Chemistry  (1)
  • chromium oxide CrO x  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of porous materials 3 (1996), S. 175-180 
    ISSN: 1573-4854
    Keywords: chromium oxalate ; chromium oxide CrO x ; nitrogen adsorption-desorption ; porosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The porosity of oxides has an influence on their catalytic activity. An accurate knowledge of the effects of thermal treatments on the textural characteristics of oxides obtained by precursors decomposition is therefore an essential step. The porosity of the studied chromium oxides was analyzed by nitrogen adsorption-desorption measurements. Decomposition under air at 310–340°C of chromium oxalate allowed us to obtain more or less microporous X-ray amorphous chromium oxides, CrO x (x ≈ 2), according to the heating and cooling rates and the treatment temperatures used. The oxides obtained from chromium hydroxides were mesoporous and had lower specific surface areas. Using high heating and cooling rates for the oxalate decomposition, the prepared chromium oxides were more microporous. By this way, the control of the textural properties of the resulting oxides is possible.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-1948
    Keywords: Chromium ; Carboxylate complexes ; Metal-metal multiple bonds ; Molybdenum ; Rhenium ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Re2{μ-O2CC(CH3)3}4Cl2 with [(CO)5M-CN]Na (M = Cr, Mo, W) leads to tetranuclear complexes of formula Re2{μ-O2CC(CH3)3}4[-NC-M(CO)5]2 (M = Cr, Mo, W). These complexes were characterized by 1H-, 13C-, and 95Mo-NMR, IR and Raman spectroscopy, elemental analysis and examined by cyclic voltammetry. The applied methods show the donor capabilities of the [(CO)5M-CN]- ligands which shift electron density towards the Re centers weakening the Re-Re quadruple bond. The Re-Re bond lengths and the ν(Re-Re) force constants are estimated based on the FT-IR and Raman examinations. Photochemical examinations and TG/MS experiments have also been conducted. The latter method shows that the product complexes decompose around 100 °C, by first loosing their carbonyl substituents; as do the Cr, Mo, W precursor compounds. The dirhenium tetrapivalate unit decomposes only at higher temperatures in a distinct second step.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 313-323 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Using the dressed molecule picture of molecule radiation interactions (A.D. Bandrauk et al., J. Chem. Phys., 79, 3256; 80, 4926; 83, 2840) one can deduce multiphoton processes (absorption, scattering, nonlinear optical properties, etc.) amplitudes from coupled second-order differential equations with electronic surfaces and transition moments as input data obtainable from quantum chemical calculations. The present approach enables one to include in the calculation bound and continuum states simultaneously by the use of appropriate boundary conditions for the numerical solutions of these coupled equations. In the case of weak radiative couplings, one recovers the usual Fermi-Golden rule expressions for electronic absorption, raman scattering, etc. The method is thus quite general, bridging the weak field (traditional photochemistry) and the strong field (laser chemistry) regimes which are attainable with today's lasers. The numerical solutions of the coupled equations give us the stationary states of the molecule + radiation system, called dressed molecule. Preparation of the initial state can be mimicked in the coupled equations by an artificial channel method for processes involving a final-state dissociation. Examples of such calculations will be presented in the diatomic Cl2 for which several ab initio electronic states and transition moments were available.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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