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  • 1
    Electronic Resource
    Electronic Resource
    Electron-Transfer Chemistry and Redox-Switching of Stilbene-Like Heteroaromatic Compounds  -  Syntheses, Optoelectrochemical and ESR/ENDOR StudiesDedicated to Prof. M. Hanack on the occasion of his 65th birthday. (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 2069-2077 
    Details
    ISSN: 0947-3440
    Keywords: Stilbenes ; Push-pull substitution ; Electron transfer ; (Z)/(E) Isomerisation ; Radical ions ; Cyclic voltammetry ; Spectroelectrochemistry ; ESR / ENDOR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Redox-active compounds, in which the electron donor and the acceptor subunits are covalently linked by a vinylene spacer group were synthesised and their properties were investigated by cyclovoltammetry, spectroelectrochemistry, and ESR/ENDOR spectroscopy.  -  10-Methylphenothiazinyl, 10-methylphenoxazinyl, and phenoxathiinyl were used as electron-donating groups whereas 9,10-anthraquinon-2-yl and phenyl groups were employed as acceptors. The synthesis of the push-pull-substituted stilbenes 1a, 1b, 1c, 2a, 2b and 2c was achieved by Wittig coupling of the heterocyclic aldehydes with the anthraquinoyl or phenyl phosphonium salts. The diastereoisomers were separated either by chromatography or by crystallization.  -  The redox potentials of the (Z) and (E) isomers differ only slightly. Spectroelectrochemical measurements indicate that the radical cations of the phenothiazine and phenoxazine derivatives undergo rearrangement from the (Z) to the (E) isomers. On the other hand, electron attachment leads to configurationally stable radical anions. This behaviour is rationalised in terms of the electron distribution reflected by the hyperfine data established by ESR/ENDOR spectroscopy.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961218
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  • 2
    Electronic Resource
    Electronic Resource
    Solution Structure of One-Electron Reduced and Oxidized Molecules with Twisted Donor and Acceptor Moieties (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1466-1474 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution structures of the radical anion and the radical cation of the donor-acceptor molecules 3,4-di(1,3-dithiol-2-ylidene)-4-phenylbut-1-ene-1,1-dicarbonitrile (1) and 3,4-di(1,3-dithiol-2-ylidene)-4-phenylbut-1-ene-1,1,2-tricarbonitrile (2) are discussed based on cyclovoltammetric and ESR/ENDOR measurements. It is shown that the spin population of the radical anions is limited to the di- and tricyanoethene moiety and the coplanar 1,3-dithiole at C(3), whereas that of the radical cations resides mainly inside the two 1,3-dithiole rings. The energies of the long-wave bands in the electronic-absorption spectra of 1 and 2 correspond to the differences between the oxidation and reduction potentials and thus point to a charge-transfer character of these transitions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770524
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of non-planarity on the spin distribution in the radical anions containing the stilbene or the azobenzene π-system: An ESR and ENDOR Study (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 307-318 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical anions of 5H-dibenzo[a,d]cycloheptene (9), 5 H-dibenzo[c,f][1,2]diazepine (10), 5,6-dihydrodibenzo[a,e]cyclooctene (11), 5,6-dihydrodibenzo[c,g][1,2]diazocine (12), and (E)-2,2,5,5-tetramethyl-3,4-diphenylhex-3-ene (13) were characterized by ESR and ENDOR spectroscopy. Their hyperfine data were compared with those previously reported for radical anions also containing the stilbene or the azobenzene π-system. Whereas the π-spin distribution in the radical anions of the stilbene series is only moderately sensitive to deviations of the π-system from planarity, the radical anions of the azobenzene series respond to steric strain by shifting the π-spin population from the benzene rings to the azo group. This finding is impressively demonstrated by the similar hyperfine data for 9· - and 11· - which contrast with the strongly highly hindered 13· -. A. plausible interpretation is readily provided by the electron affinities of the constituent π-moieties in stilbene and azobenzene. While those of benzene and ethene are both comparatively low, the azo group has a considerably higher electron affinity.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790130
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  • 4
    Electronic Resource
    Electronic Resource
    Radical Anions of Polyalkylazulenes: An ESR and ENDOR Study (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1458-1465 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton-hyperfine data are reported for the radical anions generated from azulene (1) and its alkyl derivatives 2-11 in 1,2-dimethoxyethane both ‘chemically’ with K and electrolytically. The alkyl derivatives are 1,3-dimethyl- (2), 5,7-dimethyl- (3), 1,3,5,7-tetramethyl- (4), 2-methyl- (5), 4,6,8-trimethyl- (6), 2,4,6,8-tetramethyl-(7), 1,3,4,6,8-pentamethyl- (8), 1,3,4,8-tetramethyl-6-propyl- (9), 6-(tert-butyl)-1,3,4,8-tetramethyl- (10), and 1,2,3,4,6,8-hexamethylazulene (11). Alkyl substituents at the odd-numbered centers μ = 1, 3, 5, and 7 partly shift the π-spin population from the seven- to the five-membered ring, whereas those at the even-numbered centers μ = 4, 6, and 8 exert an opposite effect on the π-spin distribution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770523
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of a p-Terphenoquinone and Paramagnetic Species Derived TherefromPart 12 of ‘Quinones’. Part 11: [1]. (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1739-1751 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,5,3″,5″-Tetra(tert-butyl)-p-terphenoquinone (12b) was synthesized and characterized by its spectroscopic and X-ray structural data. The ground state of 12b is singlet with a strong contribution of a biradical structure. Paramagnetic derivative of 12b, such as the semiquinone radical anion (12bτ) and its O-protonated form, the phenoxy radical (18), were studied by ESR and ENDOR spectroscopy.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760430
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  • 6
    Electronic Resource
    Electronic Resource
    Paramagnetic Redox Stages of a Bisphane: An ESR and ENDOR Study (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 2307-2316 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Seven redox stages, the dication 12+, the radical cation \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document}, the neutral 1, the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, the dianion 12-, the radical trianion \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document}, and the tetraanion 14-, are indicated by cyclic voltammetry for the bisphane 1, in which the benzene decks of two lateral paracyclophane moieties are orthogonal to the plane of anthracene framework. In \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, the unpaired electron is accommodated into the central anthracene subsystem, and the same statement holds for the two positive or negative charges in 12+ and 12-. Formation of \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document} and 1- occurs through admission of additional electrons one-by-one into the two paracyclophane moieties flanking the doubly charged anthracene subsystem in 12-. The above-postulated, successive release or uptake of electrons by the individual parts of the bisphane is in perfect accord with the hyperfine data determined by ESR and ENDOR spectroscopy for \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{+}\kern-4pt {.}\kern-2pt }}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$1^{\scriptstyle {3{\relbar}\kern-4pt {.}\kern-2pt }}$\end{document}\end{document}, as well as for radical ions of suitable reference compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750717
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  • 7
    Electronic Resource
    Electronic Resource
    Radical cations of precursor compounds for organic conductors derived from carbohydrates: An ESR study (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. S94 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; ENDOR ; organic conductors ; radical cation ; 1,3-dithiol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cations of two electron donors containing two 1,3-dithiol moieties were characterized by the use of ESR/ENDOR/general TRIPLE spectroscopy. The spin population resides mainly in the central part of the molecules. The g-factors are correlated with the 33S coupling constants, which are determined from satellite lines.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331315
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