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  • 1
    Digitale Medien
    Digitale Medien
    Theoretical studies on the photochromic processes of 4-bromo-N-salicylideneaniline (1995)
    Springer
    Theoretical chemistry accounts 92 (1995), S. 297-303 
    Details
    ISSN: 1432-2234
    Schlagwort(e): AM1 method ; Photochromism ; 4-bromo-N-salicylideneaniline
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary In the present paper, we carry out a semiempirical SCF MO AM1 investigation on the photochromic mechanism of 4-Br-N-salicylideneaniline (BrSA). Optimized equilibrium geometries and the nature of the excited-state potential energy surfaces are consistent with experimental findings. The calculated excited-state potential energy profiles can semiquantitatively explain the experimental facts. The photochromic processes which are initiated by excitation of the enol form to its first excited singlet state S1 involve the proton transfer from the hydroxyl oxygen to the imine nitrogen via six-membered ring transition states. Theoretical studies show that the proton transfer from the S1 state produces the keto form either on excited singlet state S'1 or on triplet state T'1 which may further decay to the ground state via radiative or nonradiative processes. The ultimate product of the photochromic reaction is mainlytrans-ketoamine with partial zwitterion character. All of these have been confirmed by the experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01113869
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  • 2
    Digitale Medien
    Digitale Medien
    Study of hydrolytic kinetics of the hexachlorostannate anion by two-dimensional 119Sn exchange spectroscopy (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 836-840 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 2D 119Sn EXSY ; Hexachlorostannate anion ; Hydrolysis ; Rate constants ; Equilibrium constants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two-dimensional 119Sn exchange spectroscopy was applied to study the hydrolytic kinetics of the hexachloro-stannate anion, SnCl62-. Two 119Sn exchange spectra for SnCl4 · 5H2O solutions with various HCl concentrations are presented. Magnetization exchanges, which are related to the hydrolysis processes, occur in the SnCl62- hydrolysis series. The exchange rate constants, the hydrolysis rate constants and the hydrolysis equilibrium constants were evaluated.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260270905
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  • 3
    Digitale Medien
    Digitale Medien
    Nuclear quadrupole coupling constants of halogenated hydrocarbons and their relation to the natural hybrid orbitals (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 36-39 
    Details
    ISSN: 0749-1581
    Schlagwort(e): NQR ; Natural hybrid orbitals ; Halogenated hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The natural hybrid orbitals of halogen atoms in various halogen-substituted alkanes and benzenes have been calculated by the Fenske-Hall MO SCF method and natural hybrid orbital theory. Four consistent parameters i, s, d and π are derived to describe the nuclear quadrupole coupling constant (QCC) of the halogen isotopes 35Cl, 81Br and 127I, with modification by the asymmetry parameter η. A semi-empirical expression is proposed from a different point of view.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260320108
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