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  • Inorganic Chemistry  (1)
  • Key words Carbonmonoxy-Myoglobin  (1)
  • Key words Chlorites  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Mössbauer and molecular orbital study of chlorites (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 258-269 
    Details
    ISSN: 1432-2021
    Keywords: Key words Chlorites ; Iron lattice sites ; Mössbauer spectroscopy ; Molecular orbital calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  The different Fe2+ lattice sites in iron-rich chlorites have been characterized by Mössbauer spectroscopy and molecular orbital calculations in local density approximation. The Mössbauer measurements were recorded at 77 K within a small velocity range (±3.5 mm s−1) to provide high energy resolution. Additionally, measurements were recorded in a wider velocity range (±10.5 mm s−1) at temperatures of 140, 200, and 250 K in an applied field (7 T) parallel to the γ-beam. The zero-field spectra were analyzed with discrete Lorentzian-shaped quadrupole doublets to account for the Fe2+ sites M1, M2, and M3 and with a quadrupole distribution for Fe3+ sites. Such a procedure is justified by the results obtained from MO calculations, which reveal that different anion (OH−) distributions in the first coordination sphere of M1, M2, and M3 positions have more influence on the Fe2+ quadrupole splitting than cationic disorder. The spectra recorded in applied field were analyzed in the spin-Hamiltonian approximation, yielding a negative sign for the electric field gradient (efg) of Fe2+ in the M1, M2, and M3 positions. The results of the MO calculations are in quantitative agreement with experiment and reveal that differences in the quadrupole splittings (ΔE Q ), their temperature dependence and in the isomer shifts (δ) of Fe2+ in M1, M2, and M3 positions can theoretically by justified. Therefore, the combined Mössbauer and MO investigation shows that the three Fe2+ lattice sites in the chlorites investigated here can be discriminated according to their ΔE Q -δ parameter pairs. With the calculated average iron-oxygen bond strength, the MO study provides an explanation for the observed trend that the population of the three lattice sites by Fe2+ increases according to the relation M1 〈 M2 〈 M3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050255
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  • 2
    Electronic Resource
    Electronic Resource
    Low temperature study of myoglobin-ligand rebinding kinetics with Mössbauer spectroscopy (1997)
    Springer
    European biophysics journal 26 (1997), S. 227-237 
    Details
    ISSN: 1432-1017
    Keywords: Key words Carbonmonoxy-Myoglobin ; Recombination kinetics ; Mössbauer spectroscopy ; Scaling law ; Activated tunneling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have studied the recombination kinetics of carboxymyoglobin (after photodissociation of the CO ligand) by Mössbauer spectroscopy for temperatures in the range 4.2 – 60 K. The observed kinetics display non-exponential behaviour which was monitored over periods of a few days. It is shown that the time dependence of the kinetics can be reduced to a single universal function of the temperature-dependent variable (t/τ 1/2(T)) β(T) . The half-decay time τ 1/2(T) and the scaling parameter β(T) are analysed for the presence of tunneling effects. The non-Arrhenius temperature dependence of the half-decay time below 60 K is interpreted as activated tunneling in models with an Eckart barrier or a fluctuating barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050075
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  • 3
    Electronic Resource
    Electronic Resource
    Darstellung von Metall-Schwefel-Clustern durch einfache Reaktion von Metallsalzen mit H2S: R2(NH4)[Cu3S12], R2[Cu4S12] · CH3CN, R2[Cu4S12,8], R2[Fe2S2(S5)2], R2[Fe4S4Br4], R2[Fe4S4Br2Cl2], R2[Fe4S4Cl4], R2[Fe2S2Cl4] (R = PPh4) und [Fe(DMF)6][Fe2S2Cl4]Professor Friedo Huber zum 60. Geburtstage am 4. Juni 1989 gewidmet (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 570 (1989), S. 7-36 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Metal-Sulfur-Clusters by Simple Reaction of Metal-Salts with H2S: R2(NH4) [Cu3S12], R2[Cu4S12] · CH3CN, R2[Cu4S12,8], R2[Fe2S2(S5)2], R2[Fe4S4Br4], R2[Fe4S4Br2Cl2], R2[Fe4S4Cl4], R2[Fe2S2Cl4] (R = PPh4) and [Fe(DMF)6][Fe2S2Cl4]Simple preparation methods for metal sulfur clusters from simple metal salts and H2S in solution are reported (for the systems Cum+/H2S and Fen+/H2S). The compounds R2(NH4)[Cu3S12], R2[Cu4S12] · CH3CN, R2[Cu4S12,8], R2[Fe2S2(S5)2], R2[Fe4S4Br4], R2[Fe4S4Br2Cl2], R2[Fe4S4Cl4], R2[Fe2S2Cl4] (R = PPh4) and [Fe(DMF)6][Fe2S2Cl4] were characterized spectroscopically (IR, Raman, Fe-Mössbauer) and by complete crystal structure analyses (except R2[Fe2S2(S5)2] and R2[Fe2S2Cl4]).For structural data see Inhaltsübersicht.
    Notes: Es wird über eine einfache Darstellungsmöglichkeit von Metall-Schwefel-Clustern aus einfachen Metall-Salzen und H2S in Lösung berichtet und zwar für die Systeme Cum+/H2S und Fen+/H2S. Die Verbindungen R2(NH4)[Cu3S12], R2[Cu4S12] · CH3CN, R2[Cu4S12,8], R2[Fe2S2(S5)2], R2[Fe4S4Br4], R2[Fe4S4Br2Cl2], R2[Fe4S4Cl4], R2[Fe2S2Cl4] (R = PPh4) und [Fe(DMF)6][Fe2S2Cl4] wurden spektroskopisch (IR, Raman, Fe-Mößbauer) sowie durch vollständige Kristallstrukturanalyse charakterisiert (mit Ausnahme von R2[Fe2S2(S5)2]).(PPh4)2(NH4)[Cu4S12]: P1, a = 1266,0(5), b = 1 489,6(6), c = 1 493,6(6) pm, α = 74,72(3), β = 86,40(3), γ = 77,52(3)°, V = 2 652,9 · 106 pm3, Z = 2; R = 0,057 für 8377 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).(PPh4)2(NH4)[Cu4S12] · CH3CN: P1, a = 1 062,2(3), b = 1 336,2(4), c = 2 137,8(6) pm, α = 102,42(2), β = 90,60(2), γ = 110,16(2)°, V = 2 769,8 · 106 pm3, Z = 2; R = 0,076 für 4312 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).(PPh4)2[Cu4S12,8]: P21/n, a = 1 245,2(8), b = 1 306,9(10), c = 3348,7(22) pm, β = 98,90(5°), V = 5383,9 · 106 pm3, Z = 4; R = 0,094 für 4814 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).(PPh4)2[Fe4S4Br4]: C2/c, a = 1585,8(6), b = 1440,6(4), c = 2419,7(9) pm, β = 112,74(3)°, V = 5 098,1 · 106 pm3, Z = 4; R = 0,068 für 3 247 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).(PPh4)2[Fe4S4Br2Cl2]: C2/c, a = 1592,3(3), b = 1432,9(3), c = 2325,0(5) pm, β = 106,43(2)°, V = 5 088,1 · 106 pm3, Z = 4; R = 0,084 für 1982 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).(PPh4)2[Fe4S4Cl4]: C2/c, a = 1593,9(3), b = 1420,8(2), c = 2316,9(4) pm, β = 106,65(1)°, V = 5026,9 · 106 pm3, Z = 4; R = 0,069 für 3 902 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).[Fe(DMF)6][Fe2S2Cl4]: P1, a = 923,5(4), b = 941,4(4), c = 1123,9(5) pm, α = 75,29(4), β = 71,17(3), γ = 87,27(4)°, V = 893,9 · 106 pm3, Z = 1; R = 0,067 für 1832 unabhängige Reflexe (Fo 〉 3,92 σ(Fo)).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895700102
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