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  • 1
    Electronic Resource
    Electronic Resource
    Conformers of Saturated Chains: Matrix Isolation, Structure, IR and UV Spectra of n-Si4Me10Dedicated to Professor H.-D. Scharf on the occasion of his 65th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 529-538 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; conformation ; sigma conjugation ; matrix isolation ; oligosilanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared and ultraviolet spectra of the gauche and anti conformers of matrix-isolated permethyl-n-tetrasilane have been obtained separately by taking advantage of thermally induced gauche-to-anti conversion and of wavelength-selective photochemical destruction of either conformer. The resolved UV spectrum of the gauche conformer provides the first piece of experimental evidence in favor of the recently proposed reinterpretation of conformational effects on tetrasilane electronic states. According to this, it is not the energy but the intensity of the lowest singlet excitation that changes dramatically as the SiSiSiSi dihedral angle is varied, as a result of an avoided crossing between s̰s̰* and s̰π* states. Implications for the general understanding of sigma conjugation in simple terms are discussed. Unconstrained MP2/6-31 G* optimization predicts the existence of a third backbone conformer (ortho), with a dihedral angle of about 90°. Its predicted (HF/3-21 G*) mid-IR spectrum is indistinguishable from that of the gauche conformer, and the matrix-isolation spectra thus provide no evidence for or against its presence.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020512
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular and biomolecular electronics (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 237-238 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Optical recording by a 823-nm GaAlAs laser, based on stretched-polymer birefringence relaxation (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 2331-2336 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A ∼5-μm-thick stretched sheet of a vinyl chloride-vinyldene chloride copolymer containing a suitable polymethine dye providing an optical density of 1-2 at 823 nm has been used to record ∼3μm-diameter relaxed spots, produced with pulses of 250 μs or longer from a 5-mW GaAlAs laser operating at 823 nm. The spots have been observed under polarizing microscope. It is proposed that this demonstrates a principle that could be used for recording and retrieval of information by a laser beam, using a stretched polymer as the storage medium.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310730
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  • 4
    Electronic Resource
    Electronic Resource
    Design of a positive resist for projection lithography in the mid-UV (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 1004-1011 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The design, synthesis, formulation, and process optimization of a new mid-UV resist are described. The synthesis of a spectrally matched sensitizer was guided by semiempirical quantum mechanical calculations that predict the effect of structural changes on optical absorption characteristics. The formulation was guided by computer profile simulation studies and the process development by a response surface analytical procedure. These techniques allowed formulation optimization to be achieved on the basis of an understanding of the complex interactions between the resist dissolution response functions and the modulation transfer function of the exposure tool for which the resist was designed.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760231806
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  • 5
    Electronic Resource
    Electronic Resource
    Reactive Molecules. The Neutral Reactive Intermediates in Organic Chemistry. Von C. Wentrup. Wiley, Chichester 1984. XI, 333 S., geb. £ 33.20. - ISBN 0-471-87639-9 (1985)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 97 (1985), S. 1005-1005 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19850971140
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  • 6
    Electronic Resource
    Electronic Resource
    Neutrale und geladene Diradikale, Zwitterionen, Trichter auf der S1-Hyperfläche und Protonentranslokation; ihre Bedeutung für den Sehvorgang und andere photochemische und photophysikalische Prozesse (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 99 (1987), S. 216-236 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Um die Struktur von Photoprodukten verstehen zu können, ist es wesentlich, diejenigen Geometrien zu kennen, bei denen Moleküle aus angeregten Zuständen in den Grundzustand (S0) zurückkehren. In Frage kommen dabei vor allem Geometrien, die lokalen Minima auf den Potentialhyperflächen der S1- (energieärmstes angeregtes Singulett) oder T1-Zustände (energieärmstes Triplett) oder konischen Durchschneidungen („Trichter“, „Funnels“) der Hyperflächen der S0- und S1-Zustände entsprechen. Obwohl für ausreichend kleine Moleküle derartige Geometrien heute bereits, wenn auch mit großem Aufwand, numerisch bestimmt werden können, wären qualitativere, damit aber zugleich allgemeinere Aussagen über diejenigen Geometrien photochemischer Systeme, bei denen sich die Hyperflächen der S0- und S1-Zustände nähern, von Interesse. Viele dieser Geometrien sind mit einem diradikaloiden Charakter des Systems verknüpft, so daß es sinnvoll ist, die Eigenschaften von Diradikalen und verwandten Spezies eingehender zu untersuchen. Nach einem Überblick über das Zweielektronen-Zweiorbitale-Modell für Moleküle mit Diradikaloid-Geometrien werden die Bedingungen für eine Berührung von S0- und S1-Hyperflächen formuliert. Gestützt werden die Ergebnisse des einfachen Modells durch die umfangreicher ab-initio-Konfigurationswechselwirkungs(CI)rechnungen für die Verdrillung von Ethylen im polarisierenden Feld einer positiven Ladung, für die Verdrillung um geladene Doppel-bindungen und um Einfachbindungen zwischen π-Donor und π-Acceptor, sowie durch die Ergebnisse ähnlicher Rechnungen für „push-pull“-substituierte Cyclobutadiene. In einigen Fällen werden nahezu entartete S0-, S1- und T1-Zustände vorhergesagt. Die naheliegenden Konsequenzen, die aus diesen Befunden für die mechanistische Beschreibung der cis-trans-Isomerisierung, der Bildung von TICT-Zuständen (Twisted Intramolecular Charge Transfer), der Protonentranslokation und - möglicherweise - des ersten Schritts beim Sehvorgang zu ziehen sind, werden zusammengefaßt. Darüber hinaus sind die Ergebnisse wichtig für das Verständnis der Regiospezifität von Singulett-Photocycloadditionen.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19870990308
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  • 7
    Electronic Resource
    Electronic Resource
    Triazoles. XIVFor Part XIII, see Ref. 1. - 15N NMR study of substituted 5-amino-1,2,4-triazolesPresented in part at the Annual Conferenc of the Hungarian Chemical Society, Debrecen, Hungary, 1987, and at the 9th Symposium on the Chemistry of Heterocyclic Compounds, Bratislava, Czechoslovakia, 1987. (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 1-3 
    Details
    ISSN: 0749-1581
    Keywords: 15N NMR ; 5-Amino-1,2,4-triazoles ; Tautomerism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N NMR chemical shifts were measured for a series of substituted 5-amino-1,2,4-triazoles. The assignment of isomeric structures agrees with earlier results obtained with the use of proton-coupled 13C NMR.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260270102
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  • 8
    Electronic Resource
    Electronic Resource
    Book Review: Reactive Molecules. The Neutral Reactive Intermediates in Organic Chemistry. By C. Wentrup (1986)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 25 (1986), S. 295-296 
    Details
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198602951
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  • 9
    Electronic Resource
    Electronic Resource
    Neutral and Charged Biradicals, Zwitterions, Funnels in S1, and Proton Translocation: Their Role in Photochemistry, Photophysics, and Vision (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 26 (1987), S. 170-189 
    Details
    ISSN: 0570-0833
    Keywords: Free radicals ; Zwitterions ; Diradicals ; Quantum chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A knowledge of the geometries at which excited molecules return to the electronic ground state (S0) is essential for the understanding of the structures of photoproducts. Particularly good candidates are geometries corresponding to local minima on the S1 (lowest excited singlet) and T1(lowest triplet) surfaces, as well as S0-S1 conical intersections (funnels). Given sufficient effort, such geometries can nowadays be found numerically for small enough molecules. Still, it is interesting to ask whether more approximate, but also more general, statements can be made concerning the geometries at which the S0 and S1 surfaces closely approach each other. Since many of these are biradicaloid geometries, it is logical to examine the properties of biradicals and related species at some length. After reviewing the two-electron two-orbital model for molecules at biradicaloid geometries, we formulate the conditions under which the S0 and S1 surfaces touch. The results obtained for the simple model are supported by ab initio large-scale configuration interaction (CI) calculations for the twisting of ethylene in the polarizing field of a positive charge and for the twisting of charged double bonds and π-donor-to-π-acceptor single bonds, and by similar calculations for “push-pull” perturbed cyclobutadienes, some of which are predicted to have nearly degenerate S0, S1, and T1 states. The likely consequences of these results for the detailed description of the mechanisms of cis-trans isomerization, the formation of twisted internal charge-transfer (TICT) states, proton translocation, and possibly of the initial step in vision, as well as for the understanding of the regiospecificity of singlet photocycloaddition, are summarized.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198701701
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