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  • 1
    Electronic Resource
    Electronic Resource
    Das gelbe Isomere der (1,5-Diphenylformazanyl)glyoxylsäure (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1477-1479 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Yellow Isomer of (1,5-Diphenylformazanyl)glyoxylic AcidThe yellow isomer is shown to be 4,4-dihydroxy-l-phenyl-3-phenylazo-2-pyrazolin-5-one (3), the hydrate of the pyrazolin-4,5-dione 4. Treatment of 4 with a solution of potassium -tert- butoxide in dimethylsulfoxide leads to the formation of a radical anion identified as 5 by ESR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120443
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  • 2
    Electronic Resource
    Electronic Resource
    1,4-Dihydro-1,2,4-benzotriazin-Radikalkationen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2423-2430 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,4-Dihydro-1,2,4-benzotriazine Radical Cations1,4-Dihydro-1,2,4-benzotriazinyl radicals (4) are protonated in the presence of strong acids. The structure of the radical cations was confirmed by ESR studies of deuterated derivatives.
    Notes: 1,4-Dihydro-1,2,4-benzotriazinyl-Radikale (4) werden in Gegenwart starker Säuren protoniert. Die Konstitution der Radikalkationen wurde durch ESR-spektroskopische Untersuchung deuterierter Derivate gesichert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19811140709
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  • 3
    Electronic Resource
    Electronic Resource
    2,3-Diphenyl-2,3-diazabicyclo[2.2.2]octan (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1076-1079 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,3-Diphenyl-2,3-diazabicyclo[2.2.2]octaneThe title compound 5 was synthesized by twofold arylation of 2,3-diazabicyclo[2.2.2]oct-2-ene (1). The conformational features of 5 are discussed using 1H NMR and PE data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120332
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  • 4
    Electronic Resource
    Electronic Resource
    Verdazyls, 27. 1,1′,5,5′-Tetraphenyl-3,3′-biverdazyl, the Primary Bisverdazyl (1980)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 2049-2051 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Verdazyle, 27. 1,1′,5,5′-Tetraphenyl-3,3′-biverdazyl, das primäre BisverdazylDie Titelverbindung 3 wurde dargestellt. Die gefundenen Nullfeldaufspaltungsparameter |D′| = 305 G und |E′| ≍ 0 G entsprechen der Struktur.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19801130543
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  • 5
    Electronic Resource
    Electronic Resource
    On the Homoconjugation of Two Acceptor Groups (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1615-1623 
    Details
    ISSN: 1434-193X
    Keywords: Homoconjugation ; Cyclovoltammetry ; ESR spectroscopy ; Diketones ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclovoltammetric investigations have been carried out on 3,3,6,6-tetramethylcyclohexane-1,2,4,5-tetrone (4), bicyclo-[3.2.2]nonane-6,7,8,9-tetrone (5), and several of their congeners, such as 6,13-dihydro-6,6,13,13-tetramethylquin-oxalino[2.3-b]phenazine (13), 5,10-dihydro-5,5,10,10-tetra-methylpyrazino[2,3-g]quinoxaline (17), and 6,13-dihydro-6,13-propanoquinoxalino[2,3-b]phenazine (20). For 5 and 20 a large difference (ΔE° ≥400 mV) between the first and second reduction potentials was found. The ESR results of the radical anion 20•- are in support of a strong homoconjugation. ESR studies of 4•-, 13•-, and 17•- also reveal a symmetrical displacement of the unpaired electron over both acceptor groups on the ESR time scale which, however, based on the small potential difference ΔE° ≤ 200 mV can be most likely described to a fast electron exchange.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Phenazin-5(10H)-yls, 5Part 4: Ref[1].. - Intermolecular π-π Interactions (Pimerization) of tert-Butyl-Substituted Phenazin-5(10H)-yl Radicals in The Solid State: Syntheses, Crystal Structures and Magnetic Susceptibility Measurements (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 473-483 
    Details
    ISSN: 0947-3440
    Keywords: Phenazin-5(10H)-yl ; ESR spectroscopy ; Radical pairs ; π Interactions ; Dimer absorption ; Magnetic susceptibility ; Nitrogen heterocycles ; Radicals ; Magnetic properties ; Solid-state chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Introduction of tert-butyl groups into the phenazine frame-work was accomplished by treatment of 5-acetyl-5,10-dihydrophenazine (2a) with tert-butyl chloride in the presence of AlCl3. Starting from the 2,8- or 3,7-di-tert-butyl-substituted derivatives 2c and 2b, a series of phenazin-5(10H)-yl radicals (1c-i) was synthesized and characterized by ESR and EN-DOR spectroscopy. With the exception of 1c, all phenazin-5(10H)-yls were obtained in crystalline form, and for 1d-f the long-wavelength absorption band at λ ≈ 870 nm indicates intermolecular π-π interactions in the solid state. For 1d, 1e and 1h the crystal structure could be determined. The unit cell of 1d consists of eight phenazin-5(10H)-yls. Surprisingly, four of them are arranged in radical pairs, whereas the other four lie independently in the lattice. In agreement with this structure, the magnetic susceptibility results correspond to a content of 50% monoradical and an almost complete spinpairing in the radical pairs up to T = 220 K. In 1e, the four phenazin-5(10H)-yls in the unit cell are arranged in two independent radical pairs, A and B, which are characterized by close interplanar distances and short intermolecular contacts between atoms with significant spin populations. Accordingly, the susceptibility data indicate strong spin-pairing at low temperature. Due to extensive steric shielding of the phenazin-5(10H)-yl framework, the crystal structure of 1h gives no evidence of any π-π interactions between adjacent radicals. As expected, the magnetic susceptibility of 1h corresponds to that of an ordinary monoradical.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970307
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  • 7
    Electronic Resource
    Electronic Resource
    [2.2](2,5)Pyrimidinophanes: Synthesis and molecular structure (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1885-1889 
    Details
    ISSN: 0009-2940
    Keywords: Pyrimidine derivatives ; Sulfur extrusion, photolytic ; Pyrimidinophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds 1 and 2 are synthesized by photolytic sulfur extrusion from the 2,11-dithia[3.3](2,5)pyrimidinophane 17. The molecular structures of 1 and 2 are determined by X-ray structure analysis and are discussed with regard to the steric strain in these molecules. Thermolysis of [(5-methyl-2-pyrimidinyl]methyl]- or [(2-methyl-5-pyrimidinyl)methyl]-trimethylammonium hydroxide (10 or 11) does not generate 1 and 2. α-Chlorination of 2,5-dimethylpyrimidine (3) with N-chlorosuccinimide provides the required precursors 4-6.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230921
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  • 8
    Electronic Resource
    Electronic Resource
    6-Oxo- und 6-Thioxoverdazyle (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 815-822 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 6-Oxo- and 6-ThioxoverdazylsA series of persistent 6-oxo- (4a-P) and 6-thioxoverdazyls (5a-g) could be obtained by dehydrogenation of corresponding 1,4,5,6-tetrahydro-1,2,4,5-tetrazin-3(2H)-ones (2a-p) and thiones (3a-g). This reaction can also be used for the preparation of diradicals, e.g. 7 and 10. Reduction, oxidation, and spectra of the radicals were investigated. The ESR results are discussed in detail.
    Notes: Eine Reihe beständiger 6-Oxo- (4a-p) und 6-Thioxoverdazyle (5a-g) konnten durch Dehydrierung der 1,4,5,6-Tetrahydro-1,2,4,5-tetrazin-3(2H)-one (2a-p) bzw. der Thione (3a-g) erhalten werden. Diese Reaktion läßt sich auch auf die Darstellung von Diradikalen, z.B. 7 und 10, übertragen. Reduktion, Oxidation und Spektren der Radikale wurden und Spektren der Radikale wurden Untersucht. ESR-Ergebnisse werden eingehend diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210502
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  • 9
    Electronic Resource
    Electronic Resource
    [2.2](2,6)- and [2.2](2,5)Pyrazinophanes: Synthesis and Molecular Structure (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 523-533 
    Details
    ISSN: 0009-2940
    Keywords: Hofman 1,6-elimination / Pyrazine derivatives / [2.2]Pyrazinophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds 1-3 and their methyl derivatives 4-7 were synthesized 2,11-dithia[3.3]pyrazinophanes 24-26 or by Hofmann 1,6-elimination of the appropriate [(5-methyl-2-pyrazinyl)methyl]trimethylammonium hydroxides followed by dimerization of the generated 2,5-dihydro-2,5-dimethylenepyrazines. α-Chlorination of the methylpyrazines 8-10 with N-chlorosuccinimide gave the required precursors 11, 12, 14, 17 and 18. The results of the X-ray structure determinations for 1-4 and 7 which indicate an unequivocal isomer assignment are discussed with regard to steric strain in these molecules. The electronic spectra of the pyrazinophanes 7-7 are reported and compared with those of the parent methylpyrazines.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230319
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  • 10
    Electronic Resource
    Electronic Resource
    Darstellung, ESR- und ENDOR-Untersuchung von Radikalkationen des Tetraphenylhydrazins, des 5,6-Dihydro-5,6-diphenylbenzo[c]cinnolins und des Benzo[c]benzo[3,4]cinnolino[1,2-a]cinnolins (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 980-990 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Generation, ESR and ENDOR Study of Radical Cations Derived from Tetraphenylhydrazine, 5,6-Dihydro-5,6-diphenylbenzo[c]cinnoline, and Benzo[c]benzo[3,4]cinnolino[1,2-a]cinnolineRadical cations of the title compounds (1a·+, 2·+, 3·+) and of a series of derivatives (1b·+, 1ċ+, 6a·+ - ċ+) representing hydrazine radical cations were generated by oxidation. ENDOR studies of the tetraarylhydrazine radical cations 1a·+ - ċ+ confirm the hindered rotation of the aryl groups and yield a partial assignment of the hyperfine splitting constants. According to the ESR-ENDOR results of 1a·+ and 3·+ linkage of the N,N′-phenyl groups through their o-positions does not considerably flatten the conjugation system.
    Notes: Die Hydrazin-Radikalkationen der Titelverbindungen (1a·+, 2·+, 3·+) sowie einer Reihe von Derivaten (1b·+, 1c·+, 6a·+ - e·+) wurden durch Oxidation erzeugt. ENDOR-Untersuchungen der Tetraarylhydrazin-Radikalkationen 1a·+ - c·+ bestätigen die gehinderte Rotation der Arylreste und liefern eine partielle Zuordnung der HFS-Kopplungskonstanten. Nach den ESR- und ENDOR-Ergebnissen von 1a·+ und 3·+ führt die Verknüpfung der N,N′-Phenylreste über ihre o-Positionen zu keiner beträchtlichen Einebnung des Konjugationssystems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861190321
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