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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes, 8 Conformational Mobility and Crystal Structures of Porphyrin-Quinone Cyclophanes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 811-821 
    Details
    ISSN: 0009-2940
    Keywords: Porphyrin-quinone cyclophanes ; Photoinduced electron transfer ; Porphyrin cyclophanes, conformational mobility of, crystal structures of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to correlate photoinduced electron-transfer in porphyrin-quinone cyclophanes to specific molecular conformations, the internal mobility of single-and double-bridged porphyrin-quinone cyclophanes was studied by low-temperature 1H-NMR measurements. The dynamic processes observed are discussed in terms of N-H/N tautomerisation, of the rotation of the rings in the bridges, and of a specific “swinging bridge” process back and forth between two equivalent unsymmetrical conformations with a tilted orientation of the porphyrin and quinone ring planes. For comparison with the conformational situation in solution the results of X-ray structure analyses of 3(X=OMe) and 6, as representative examples of single-bridged quinone-porphyrin cyclophanes, and of the corresponding tetramethoxybenzene-bridged octamethylporphyrin cyclophane 4(X=OMe) are reported and discussed. In contrast to the previously solved crystal structure of the quinone-porphyrin-quinone cyclophane 1(X=H), all three X-ray structure analyses of the single-bridged porphyrin cyclophanes proved the existence of unsymmetrical, tilted-plane structures similar to those discussed as the stable conformations in the “swinging bridge” process.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260336
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  • 5
    Electronic Resource
    Electronic Resource
    Syntheses and Properties of New Quinone-Bridged Diphenyl- and Tetraphenylporphyrins (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 223-229 
    Details
    ISSN: 0009-2940
    Keywords: Porphyrin-quinone cyclophanes ; Photoinduced electron transfer ; Absorption and emission spectra of porphyrin-quinone cyclophanes ; Photosynthesis models ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses and spectroscopic properties of the porphyrin-quinone cyclophanes 1, 2 and 3 of which structural and/or conformational studies have recently reported[1] are described. Physical properties related to photoinduced electron-transfer reactions like redox potentials, absorption and emission spectra were determined for these compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270132
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  • 6
    Electronic Resource
    Electronic Resource
    Zinc Complexes of Porphyrin-Quinone Cyclophanes: Syntheses, Structures and Electron-Transfer-Related Properties (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 231-236 
    Details
    ISSN: 0009-2940
    Keywords: Zinc porphyrin complexes ; Porphyrin-quinone cyclophanes ; Photoinduced electron transfer ; Electron-transfer mechanism in metalloporphyrin-quinone cyclophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to increase the driving force for photoinduced electron-transfer reactions of porphyrin-quinone cyclophanes, the zinc complexes 3a-e and 4a-e were prepared from the corresponding cyclophanes of the 1 and 2 series. Electron-transfer-related properties like redox potentials and fluorescence spectra were determined for 3a-e and 4a-e. The X-ray structure analysis of 4a indicates that for the very fast and solvent-independent electron transfer in these systems a specific mechanism involving an interaction of a quinone carbonyl group with the zinc might be considered as an alternative to through-space electron-transfer.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270133
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  • 7
    Electronic Resource
    Electronic Resource
    Photoinduced electron transfer in porphyrin-quinone cyclophanes, 5. Quinone-porphyrin-quinone and quinone-porphyrin-donor cyclophanes: Syntheses, structures and electron-transfer-related properties (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2275-2283 
    Details
    ISSN: 0009-2940
    Keywords: Photosynthesis models ; Photoinduced electron transfer ; Porphyrin-quinone cyclophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To study the structure dependence of photoinduced electron transfer between porphyrins and quinones the concept of a new family of porphyrin-quinone cyclophanes with vertical arrangements of porphyrin and quinone units is presented. The syntheses of the quinone-porphyrin-quinone cyclophane 1, the prototype of this series, and of the quinone-porphyrindonor cyclophanes 12 and 14 are described. Spectroscopic data are discussed with regard to the structures involved and in relation to electron-transfer reactions occurring in these systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251016
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  • 8
    Electronic Resource
    Electronic Resource
    Photoinduced electron transfer in porphyrin-quinone cyclophanes, 6. Porphyrin-quinone cyclophanes with gradually varied acceptor strength: Syntheses and characterizations (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2285-2301 
    Details
    ISSN: 0009-2940
    Keywords: Porphyrin-quinone cyclophanes ; Photoinduced electron transfer ; Porphyrin cyclophane syntheses ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For studying intramolecular electron-transfer reactions, three groups of double- and single-bridged porphyrin-quinone cyclophanes 1-4, 5-9, and 11-14, resp., with gradual variation of quinone acceptor strengths were synthesized. As key intermediates for building up the porphyrin-cyclophane skeleton the correspondingly 3,6-substituted 1,4-bis[4-(2-formylphenyl)-butyl]-2,5-dimethoxybenzenes 15-20 were synthesized. Condensation with pyrrole yielded the doubly bridged porphyrin cyclophanes 42-45; via the bis(dipyrrolylmethyl) derivatives 46-51 and 64-67 the single-bridged porphyrin cyclophanes 58-63 and 72-75 were obtained by acidic condensation with triethyl formate. Cleavage of the methoxy groups and oxidation yielded the corresponding porphyrin-quinone systems. Some magnesium and zinc complexes of these cyclophanes are described. Spectroscopic data (MS, 1H NMR) are reported in support of the proposed structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251017
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