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  • 1
    Electronic Resource
    Electronic Resource
    Small and Medium Rings, 75. Syntheses, Photoelectron Spectra, and Photoreactivity of Polycyclic 1,5-Diketones: Transannular Interaction in the Cyclooctane-1,5-dione Fragment (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 803-813 
    Details
    ISSN: 0009-2940
    Keywords: PE spectroscopy ; Lone-pair interaction ; Orbitals, localized ; Orbitals, precanonical ; 1,5-Diketones, polycyclic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five polycyclic 1,5-diketones 1 - 4 and 6 are synthesized and studied by means of He(Iα) PE spectroscopy. Comparison of the spectra indicates significant differences in Orbital Interaction Through Bond, which is explained by computational methods, especially by analyses of the precanonical MOs. The lone pair splitting observed in diketone 1, ΔI(n)=0.75 eV, seems to be the largest one ever found in a 1,5-diketone, obviously due to a favourable zigzag topology of the σ frame. In addition, coupling reactions and photoreactivity are studied in compound 6, which seemed to be well suited for Orbital Interaction Through Space. The crystal structure of 6 and its photoproduct 21 is solved by X-ray crystallography.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240421
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  • 2
    Electronic Resource
    Electronic Resource
    Chromophore Systeme, 1. Konformation und Lichtabsorption von Hexa-1,5-dien-3,4-dion (Divinylglyoxal) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 821-826 
    Details
    ISSN: 0009-2940
    Keywords: α-Diketones, unsaturated ; Conformers, stable ; UV-Vis transition energies ; PE Spectroscopy ; 13C-NMR chemical shifts, correlation with dihedral angles CO/CO ; Calculations, STO-3G, MMP1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chromophoric Systems, 1.  -  Conformation and Absorption of Light in Hexa-1,5-diene-3,4-dione (Divinylglyoxal)Divinylglyoxal (1) is investigated by several spectroscopic and theoretical methods in order to set up a correlation between the CO/CO dihedral angle and the transition energies in unsaturated α-diketones. According to the experimental (UV, IR, 13C-NMR, PE spectroscopy and dipole moment) and theoretical (ab initio and molecular mechanics) results, 1 exists predominantly as a C2h conformer (Θco/co=180°, ΘVinyl/co=0°). The dependence of transition energies on CO/CO dihedral angles is similar in shape to that for saturated α-diketones, but is significantly shifted to lower transition energies. 13C chemical shifts respond sensitively to CO/CO dihedral angles, and the ab initio calculated curve is supported by a few experimental results.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240423
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  • 3
    Electronic Resource
    Electronic Resource
    Small and Medium Rings, 74. Syntheses and Photoelectron Spectra of 7-Azanorbornadiene and Related Compounds An Analysis with Fragment Orbitals (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 791-801 
    Details
    ISSN: 0009-2940
    Keywords: Lone-pair orientation ; Lone pair interaction ; Precanonical orbitals ; Orbitals, localized ; Calculations, ab initio STO-3G, MNDO, MM2 force field ; PE Spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He(I) photoelectron spectra (PE) of 7-azanorbornane (5), 7-azanorbornene (6), and 7-azanorbornadiene (7) as well as of related urethanes have been recorded. The syntheses of these bicyclic compounds are described in detail. A most convenient analysis of the PE spectroscopic results is based on the procedure of Heilbronner-Schmelzer on an ab initio STO-3G level. This method allows to construct fragment orbitals elucidating the orientation of the nitrogen lone pair, the through-space interaction with π bonds, and the participation of σ bond orbitals. The result is remarkable: whereas the direct interaction of localized lone-pair and π orbitals is significant in both syn;- and anti-orientation, the interaction of a localized lone pair with a precanonical fragment π orbital is completely different in the two geometries. In 6;-syn a considerable interaction matrix element FantiΨnπ=-0.71 eV comes to the fore, whereas the corresponding parameter in 6;-anti turns out to be almost zero, FantiΨnπ=+ 0.09 eV. Since 6;-syn is calculated to be more stable than 6;-anti, it is this invertomer, 6;-syn, which is likely to be responsible for the main bands in the PE spectrum of 6. The comparatively large experimental split between the first two PE bands of 6 (0.98 eV) is in accord with the 6;-syn geometry and compares well with the calculated band separation of 1.26 eV for 6;-syn.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240420
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