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  • 1
    Electronic Resource
    Electronic Resource
    Intramolecular Electron Transfer between Terminal 1,4-Dimethoxybenzene Units in Radical Cations with a [2.2](1,4)Naphthalenophane, [2.2](1,4)Anthracenophane, and Pentacene Skeleton (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1161-1170 
    Details
    ISSN: 1434-193X
    Keywords: [2.2](1,4)Naphthalenophanes ; [2.2](1,4)Anthracenophane ; Pentacene ; Cyclic voltammetry ; Radical cations ; ESR/ENDOR spectroscopy ; Intramolecular electron transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various radical cations, in which two terminal 1,4-dimethoxybenzene units are anellated to [2.2]paracyclophane (2b•+, 3b•+), [2.2](1,4)naphthalenophane (4d•+), and anthracene bridges (5•+), have been studied by ESR and ENDOR spectroscopy. In the syn- and anti-naphthalenophane radical cations 2b•+ and 3b•+ the delocalization of the unpaired electron over both π-moieties and the distinct difference between the first and second oxidation potentials, ΔE = E20 - E10, are evidence for a substantial intramolecular electronic interaction between the two electrophores. Extension of the bridge in 4d•+ and 5 by benzo anellation results in a localized radical cation. Strong intramolecular electronic interaction between the two electrophores is found in the 1,4,8,11-tetramethoxy-pentacene radical cation (5•+). The syntheses of 4d are described.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    [2.2]Paracyclophane-4,7,12,15-tetrone, [2.2](1,4)Naphthalenophane-4,7,14,17-tetrone, and 1,4,8,11-Pentacenetetrone Radical Anions - A Comparative ESR Study (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 221-227 
    Details
    ISSN: 1434-193X
    Keywords: 1,4-Benzoquinones ; [2.2]Paracyclophanes ; 1,4,8,11-Pentacenetetrones ; Cyclic voltammetry ; Radical anions ; ESR/ENDOR spectroscopy ; Intramolecular electron transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three types of tetrone radical anions in which two 1,4-benzoquinone units are connected by ethano (1·-, 2·-), [2.2]paracyclophane (3·-, 4·-), and anthracene bridges (5·-, 6·-) have been studied by ESR and ENDOR spectroscopy. The displacement of the unpaired electron over the two π moieties in the [2.2]cyclophane radical anions 1·--4·- and the marked difference between the first and second reduction potentials, ΔE = |E20 - E10| ≥ 0.20 V, are evidence for a substantial intramolecular electronic interaction between the two electrophores. Similar ΔE data for the syn- (3) and anti-naphthalenophanes (4) indicate that most of the intramolecular electronic interaction takes place through the [2.2]paracyclophane bridge. When ion pairing is inhibited by complexation of the cation, the unpaired electron in 5·- and 6·- is also delocalized over the whole pentacenetetrone system at temperatures as low as 160 K.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Intramolecular Electron Transfer between 2,5-Dimethoxy-1,4-phenylene Units in [n.n]Paracyclophane Radical Cations (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 139-148 
    Details
    ISSN: 1434-193X
    Keywords: Paracyclophanes ; Cyclic voltammetry ; Radical cations ; ESR/ENDOR spectroscopy ; Intramolecular electron transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A range of [n.n]paracyclophane radical cations (4·+-12·+), in which two 2,5-dimethoxy-1,4-phenylene units are connected by alkano bridges of varying length, have been studied by ESR and ENDOR spectroscopy. In the [2.2]- and [3.3]paracyclophane radical cations 4·+-6·+, 10·+ and 11·+ the delocalization of the unpaired electron over both π-moieties and the distinct difference between the first and second oxidation potentials, ΔE = E20 - E10, are evidence for a strong intramolecular electronic interaction between the two electrophores. The [5.5] and [7.7] species (8·+ and 9·+) are localized radical cations at low temperature (ca. 220 K). At room temperature, the higher molecular flexibility leads to a significant increase in the number of internal collisions between the electrophores, resulting in a fast (ESR time scale) intramolecular electron transfer. The intermediate [4.4]paracyclophane radical cations 7·+ and 12·+ are apparently also localized radical cations. The close interplanar distance between the two π-moieties, however, facilitates their mutual contacts. In 7·+, the intramolecular electron transfer becomes fast on the ESR time scale at room temperature; in 12·+ the transfer is fast over the temperature range 200-300 K.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    ENDOR and triple resonance studies of 1,4-dihydro-1,2,4-benzotriazinyl radicals and 1,4-dihydro-1,2,4-benzotriazine radical cations (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 595-600 
    Details
    ISSN: 0749-1581
    Keywords: ENDOR ; Triple resonance spectroscopy ; 1H NMR ; 1,4-Dihydro-1,2,4-benzotriazinyl radicals ; 1,4-Dihydro-1,2,4-benzotriazine radical cations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ESR, ENDOR and triple resonance studies of 1,4-dihydro-1,3-diphenyl- (1a) and 3-tert-butyl-1,4-dihydro-1-phenyl-1,2,4-benzotriazinyl (2a) and of the corresponding radical cation 3a (2a protonated at N-4) yielded the magnitude and the sign of almost all of the 1H and 14N hyperfine coupling (HFC) constants. Their assignment was performed using various 2H labelled and/or methyl substituted derivatives. Both radical groups show major hyperfine coupling to the three 14N nuclei. In the uncharged species 1a and 2a, the spin density at N-4 apparently directs the 1H HFC pattern in the 1,2,4-benzotriazinyl component, a(H-5) and a(H-7) being larger than a(H-6) and a(H-8). In the radical cation, on the other hand, N-1, with an unusually large splitting of 9.9 G, is the position of highest spin density which determines the 1H HFC pattern, a(H-6) and a(H-8) being larger than a(H-7).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260712
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