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  • 1985-1989  (9)
  • 1986  (9)
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  • 1985-1989  (9)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Thermal decomposition of pentacarbonyl iron in faujasite-type zeolite X: Quantitative and reversible formation of decomposition and recombination products (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1307-1310 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract After presenting at the Alma Ata Conference our first results on the thermal decomposition of pentacarbonyl iron in zeolites of the Faujasite-type we have continued our studies by quantitatively investigating the formation of decomposition and recombination products. Our present results clearly indicate that in the first step Fe(CO)5 in zeolite X is thermally decomposed by forming zerovalent as well as divalent iron adducts. Complete desorption of CO gas yields superparamagnetic iron particles and planar-coordinated ferrous high-spin iron within the zeolite. By adding CO gas to these products (i) the iron particles react with CO forming Fe(CO)5 and other iron carbonyls as well, and (ii) the planar-coordinated iron adsorbs CO yielding spacially coordinated ferrous high-spin iron. We found these reactions to be quantitative and reversible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399474
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  • 2
    Electronic Resource
    Electronic Resource
    Paramagnetic relaxation in high-spin ferrous compounds (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1347-1350 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of three high-spin FeIIS4 complexes at various temperatures and applied magnetic fields are reported and the results are compared with those of reduced rubredoxin. Simulations of the measured spectra by means of the fully developed stochastic theory of lineshape prove that intermediate relaxation behavior is present and is determined essentially by the phonon energy distribution and by one single parameter W0, the scaling factor, which contains the strength of spin-lattice coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399483
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Mössbauer characterization of the Fe−S center in the catalytic metal binding site of alcohol dehydrogenase (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1419-1422 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Iron in its divalent and trivalent form can be substituted in the catalytic zinc site of alcohol dehydrogenase from horse liver (HLADH). Fe-HLADH in either oxidation state does not show enzymatic activity in the oxidation of ethanol. Nevertheless, Mössbauer studies of this material are of considerable interest, because they elucidate the effect of pH and coenzyme-induced conformational changes of the protein on the metal ion. It is of importance to note that zinc itself due to the lack of suitable chromophoric and magnetic properties does not provide any comparable information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399500
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  • 4
    Electronic Resource
    Electronic Resource
    A comparative theoretical study of compounds of the heavy main-group Mössbauer isotopes Sn to I (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1543-1546 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Semiempirical molecular orbital calculations are applied to calculate electric field gradients Vzz and electronic charge densities ϱ(0) at the nucleus for a series of tin- and iodine-containing compounds. The results are related with experimental isomer shifts δ and quadrupole splittings ΔEq and enable an understanding of experimental Mössbauer spectra in terms of electronic structure theory. From this correlation new values for the fractional change δR/R of the nuclear radius and for the nuclear quadrupole moment Q can be derived. A careful analysis of the various contributions to Vzz and ϱ(0) determines the range of applicability of commonly used phenomenological fitting schemes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399529
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  • 5
    Electronic Resource
    Electronic Resource
    Ab initio, Xα and IEHT Mo calculations of Mössbauer spectroscopy parameters for iron carbonyls (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1303-1306 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculations of charge density and the electric field gradient tensor at the iron nucleus by means of ab initio LCAO SCF, MS-Xα, SCC-Xα and IEHT methods for iron carbonyls Fe(CO)n, n=1–5, are presented. The calculated EFG values for the closed-shell molecule Fe(CO)5 show reasonable agreement with experiment while the values obtained for the open-shell molecules Fe(CO)n, n=1–4, significantly depend on the calculational method. Ab initio results, though using a minimal basis set, are closer to experimental data than Xα and IEHT results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399473
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence for dynamic behavior of O2 in oxyheme model compounds (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1411-1414 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have performed Mössbauer studies on several oxy-heme model compounds, and for two of them we also have derived the threedimensional structure from X-ray studies; I: [Fe(O2) (SC6HF4) TPpivP] [Na⊂18C6] and II: [Fe(O2) (SC6HF4)TPpivP] [K⊂222]. Compound I shows a pronounced temperature-dependence of ΔEQ, i. e. 2.17 mms−1 at 4.2 K and 1.55 mms−1 at 295 K, while ΔEQ of compound II is practically temperature-independent, i.e. ca. 2.05 mms−1. The X-ray structure analysis of these model compounds provides us with the fact that O2 occupies three different sites in I and only two sites in II. From the experimentally known occupancies of these sites at specific temperatures we were able to apply relaxation calculations for the electric field gradient tensors in I and II, and we found for both compounds that our calculated ΔEQ(T)-data are in agreement with our experimental results. These findings imply that the dynamic jump behavior of O2 among the different sites in oxy-heme model compounds is responsible for the temperature-dependence (like in HbO2) or temperature-independence of ΔEQ (like in cytochrome P450).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399498
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  • 7
    Electronic Resource
    Electronic Resource
    A57Fe Mössbauer study of iron assimilation inN. crassa mediated by siderophores (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1415-1418 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The siderophore coprogen is tansported in N. crassa as an entity. Neither ligand exchange nor reduction is a rate limiting step for intracellular accumulation. Metabolized iron was found predominantly to exist as fast relaxing Fe(II) high-spin (σ=1.32 mm/s, ΔEQ=2.95 mm/s) and Fe(III) high-spin species (δ=0.35−0.42 mm/s ΔEQ=0.5−0.58 mm/s). Within 27 hours, no measurable amounts of iron are transferred to ferritin like storage forms. Rather, coprogen itself serves as an intermediate iron storage compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399499
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  • 8
    Electronic Resource
    Electronic Resource
    Approximations in the theoretical interpretation of Mössbauer spectra (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1547-1550 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An account is given how semiempirical molecular orbital calculations and accurate relativistic atomic calculations can be utilized to understand Mössbauer spectra of the heavy main-group elements Sn, Sb, Te and I. The various approximations are described and it is shown in which way experimental and semiempirical theoretical information can be combined consistently to gain insight into the electronic structure of the respective compounds. A set of qualitative correlations between calculated valence orbital occupations, effective charges, coordination numbers and measured isomer shifts is derived and the limited applicability of phenomonological models is elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399530
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic measurements on stable Fe(0) microclusters. Part 2 (1986)
    Springer
    The European physical journal 3 (1986), S. 303-308 
    Details
    ISSN: 1434-6079
    Keywords: 75 ; 76 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Zero valent iron microclusters were stabilized inside the pore structure ofA-type zeolites. The cage diameter of the matrix was 1.1 nm. Mößbauer spectra show superparamagnetic behaviour down to at least 77 K. Below 10 K, slow relaxation of most of the superparamagnetic moments was observed. Information on the magnetic properties was obtained from the Mößbauer spectra below 4.2 K and from measurements in an external magnetic field applied parallel to the gamma beam. Evidence has been found for both bulk-like and non-crystalline iron clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384820
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