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  • 1
    Electronic Resource
    Electronic Resource
    Electronic States of Phenylene and Naphthylene Bicyclobutanes. Linear Dichroism in Stretched Polyethylene (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 676-686 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Excited singlet states of bicyclobutylene-benzene (2), 1,2:4,5-bis (bicyclo-butylene)benzene (3), 2,3-bicyclobutylene-naphthalene (4), and 1,8-bicyclobutylene-naphthalene (5) are investigated by means of linear dichroic absorption spectroscopy of molecules oriented in stretched polyethylene films and by semiempirical model calculations. The results indicate a strong hyperconjugative impact of the bicyclobutylene group on the aromatic chromophores in these compounds. Valence isomerization to aromatic products is predicted as the preferred photochemical pathway.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19830660231
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  • 2
    Electronic Resource
    Electronic Resource
    On Excited States of Alkyl Bridged [14] Annulenes (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 2999-3013 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The linear dichroic absorption spectrum of 1,3,6,8-trans-15, 16-hexamethyl-dihydropyrene has been measured in stretched polyethylene at 77K, and CNDO-CI calculations with inclusion of singly and doubly excited configurations have been carried out on a series of alkyl bridged [14] annulenes with pyrene- and anthracene-shaped perimeters. Transitions to e3g → e4u type 1B states are well described, and the results indicate that additional low-energy excited states originate from e3g→ e5g and e2u → e4u type configurations interacting strongly with doubly excited configurations of the e3g, e3g → e4u, e4u type. The second excited singlet state responsible for the weak transition observed between the 1L bands may be assigned to one of these additional states, but it is probably of complex nature, similar to the ‘phantom’ state in linear polyenes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610825
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic and Molecular Structure of Simple 3,3′-Bicyclopropenyls. Photoelectron Spectroscopy and Model Calculations (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 968-982 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic and molecular structure of 3,3′-bicyclopropenyl (1) and its alkyl derivatives 3,3′-dirnethyl-3,3′-bicyclopropenyl (2), dispiro [2.0.2.3]nona-1,5-diene (3), dispiro[2.0.2.4]deca-1,5-diene (4), dispiro [2.0.2.5]undeca-1, 5-diene (5), and dispiro [2.0.2.6]dodeca-1, 5-diene (6) are studied by means of photoelectron spectroscopy and model calculations. Through-bond' effects in model compound 1 are analyzed in detail, illustrating a general difficulty with NDO models. Low-energy photoelectron bands of 2-6 can be assigned to ejection of electrons from cyclo-propenyl π- and Walsh-orbitals. Strong ‘through-bond’ coupling leads to splitting of the π-bands in the range 1.0-1.5 eV, while the strongly conformation-dependent splitting of the Walsh-bands allows conclusions concerning the preferred torsional angles. The preference of a gauche-conformation is predicted for 2 in the gas phase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650329
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  • 4
    Electronic Resource
    Electronic Resource
    The Electronic Structure of Phenylene and Naphthylene Bicyclobutanes. Photoelectron spectroscopy and model calculations (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1312-1321 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoelectron (PE.) spectra of 1,2,3-methenoindane (2), 1,2,3-metheno-2,3-dihydro-1H-cyclopenta [b]naphthalene (3) and 1,2,3-metheno-2,3-dihydro-1H-phenalene (4) are investigated. The PE. spectrum of 1,3-methano-2,3-dihydrophenalene (7) is reported and compared with that of 4. The experimental results are analyzed in terms of empirical correlation diagrams and the results of semiempirical MINDO/3 and CNDO/S calculations. The analysis indicates that the strong impact of the bicyclobutylene group on the spectroscopic properties of the aromatic π-systems in 2, 3 and 4 is due to hyperconjugative interactions involving bicyclobutane Walsh orbitals.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640508
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  • 5
    Electronic Resource
    Electronic Resource
    Photoelectron Spectra of Some Reduction Products of [2.2]Paracyclophane (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1987-1990 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoelektronenspektren einiger Reduktionsprodukte von [2.2]ParacyclophanAnhand des He(I)-Photoelektronen(PE)-Spektrums von 2,3′,5,6′-Tetrahydro[2.2]paracyclophan (2) wird gezeigt, daß die Through-Bond-Wechselwirkung zwischen den Sechsringen klein, innerhalb der Cyclohexadienringe aber groß ist. Über die PE-Spektren der weiteren Hydrierungsprodukte 3 und 4 wird berichtet.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170530
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  • 6
    Electronic Resource
    Electronic Resource
    Bicyclofulvene, XI. Zur Frage der Spirokonjugation bei Spiro[cycloheptatrien-7,7′-norbornadien] (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 1000-1007 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bicyclofulvenes, XI. On the Question of Spiroconjugation in Spiro[cycloheptatriene-7,7′-norbornadiene]The title compound 4 as well as the derivatives 5 und 6 have been prepared. The first band in the UV spectrum of 4 in n-heptane is blue-shifted by ca. 20 nm with respect to those of 5 and 6. Model calculations with the CNDO/S-CI method indicate that this hypsochromic shift as well as the bathochromic shift of the corresponding band of 2 relative to that of 3, cannot be explained by spiroconjugation. The thermolysis of 4 yields benzene, heptafulvalene (15), and fulveneallene (16). The latter products are probably derived from cycloheptatrienylidene (14) as an intermediate.
    Notes: Die Titelverbindung 4 sowie die Derivate 5 und 6 wurden dargestellt. Die erste Bande im UV-Spektrum von 4 in n-Heptan zeigt eine hypsochrome Verschiebung um ca. 20 nm verglichen mit den Banden in 5 und 6. Modellrechungen mit der CNDO/S-CI-Methode zeigen, daß, sowohl diese hypsochrome Verschiebung als auch die bathochrome Verschiebung der entsprechenden Bande von 2 im Vergleich zu 3 nicht auf Spirokonjugation beruht. Die Thermolyse von 4 ergibt neben Benzol Heptafulvalen (15) und Fulvenallen (16). Diese Produkte machen eine Spaltung von 4 in Benzol und Cycloheptatrienyliden (14) wahrscheinlich.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180316
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  • 7
    Electronic Resource
    Electronic Resource
    Conjugative, Exciton and Charge-Resonance Interactions in D2d-9,9′-Spirobifluorene and D2d-Tetrabenzotricyclo [5.5.0.02,8]dodeca-3,5,9,11-tetraene. Photoelectron and Polarized Absorption Spectra (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 1441-1455 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoelectron spectroscopy, polarized electronic absorption spectroscopy in stretched polymer sheets, and semiempirical theoretical methods have been applied to investigate the valence electronic structures of the two title compounds 1 and 2, considering fluorene (3) as a reference compound. The results are analyzed in terms of ‘through space’ and ‘through bond’ conjugative effects and exciton and charge-resonance interactions. Spiro-conjugation in 1 is found to play a similar role as ‘through bond’ interaction via the cyclobutane ring in 2. In contrast to the results of a recent investigation, exciton coupling is found to be relatively insignificant, while charge-resonance effects are important. The transition close to 41 000 cm-1 in the absorption spectra of 1 and 2 has no obvious counterpart in the spectrum of 3; it is assigned to a 1E- state with large charge-resonance character, involving promotion of an electron from the HOMO of one half-chromophore to the LUMO of the other.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19830660513
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  • 8
    Electronic Resource
    Electronic Resource
    Photoelectron spectra of pteridine and its 4-methyl and 2,4,6,7-tetramethyl derivatives (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 1275-1280 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoelektronen-Spektren von Pteridin, 4-Methyl- und 2,4,6,7-TetramethylpteridinDie He(Iα)-Photoelektronen-Spektren der drei Titel-Verbindungen 1-3 wurden aufgenommen und mit Hilfe des Hückel-Modells und semiempirischer Rechnungen interpretiert. Für Pteridin (1) wird ein pKa-Wert von -2 vorausgesagt, mit einer bevorzugten Protonierung im Pyrimidinring.
    Notes: The He(Iα) photoelectron spectra of the three title compounds 1-3 have been recorded and analyzed in terms of a simple Hückel-model and of semiempirical calculations. The pKa value of pteridine (1) is predicated to be of the order of -2, with preferred protonation in the pyrimidine ring.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861190416
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  • 9
    Electronic Resource
    Electronic Resource
    Das Photoelektronen- und Elektronenspektrum des 1,3,5-Tri-tert-butylpentalens. Hinweis auf Bindungsalternanz im Grundzustand (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 932-938 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Photoelectron and Electron Spectrum of 1,3,5-Tri-tert-butylpentalene. Evidence for bond Alternance in the Ground StateThe photoelectron spectrum (He(I)) and the absorption spectrum (UV-VIS) of 1,3,5-tri-tert-butylpentalene (1) are discussed. The first four bands in the spectra are assigned by comparison with calculated orbital energies and transition energies, respectively. In the case of the absorption spectrum of 1, a good agreement between measured and calculated results is possible only if bond alternance in 1 is assumed.
    Notes: Das Photoelektronenspektrum (He(I)) und das Absorptionsspektrum (UV-VIS) von 1,3,5-Tri-tert-butylpentalen (1) werden diskutiert. Die Zuordnung der ersten vier Banden erfolgt aufgrund eines Vergleichs mit den berechneten Orbitalenergien bzw. Übergängen. Beim Absorptionsspektrum von 1 ist nur dann eine gute Übereinstimmung zwischen Experiment und Rechnung zu erzielen, wenn Bindungsalternanz bei 1 angenommen wird.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110314
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  • 10
    Electronic Resource
    Electronic Resource
    Umlagerung von Tris-σ-homobenzolen zu 1,4,7-CyclononatrienenDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft und vom Fonds der Chemischen Industrie unterstützt. (1978)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 471-472 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19780900611
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