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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and Structural Properties of Bridged 1,8-Diazacyclotetradeca-4,11-diynes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2803-2809 
    Details
    ISSN: 1434-193X
    Keywords: Alkynes ; Cyclizations ; Nitrogen heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 1,8-diazacyclotetradeca-4,11-diyne (4) was accomplished by reaction of 1,6-dibromo-3-hexyne (11) with ammonia. Similarly, the preparation of 1-azacyclotetradeca-4,11-diyne (5) was achieved from 1,13-dibromotrideca-3,11-diyne (10) and ammonia. The reaction of α,ω-diamines of linear hydrocarbons of the chain length C4 to C10 with 11 yielded the corresponding bicyclic diynes 23-29. The reaction of 4 with 11 yielded 1,8-diazabicyclo[6.6.6]icosa-4,11,16-triyne (14). Similarly, the reaction of 4 with 1,4-dibromo-2-butyne yielded 1,8-diazabicyclo[6.6.4]octadeca-4,11,16-triyne (31). The molecular structures of 1,8-diisopropyl-1,8-diazacyclotetradeca-4,11-diyne (13a), as well as of 14, 24, 27 and 31 were studied by means of the X-ray technique. It was found that 13a adopts a chair-like conformation (C2h) with an equatorial orientation of the isopropyl groups. In 14, 24, 27, and 31 the 14-membered rings adopt a twist-boat conformation. The distance between the nitrogen atoms varies between 4.662(2) and 5.189(2) Å. In the case of 14, 24 and 27 the nitrogen atoms are pyramidalized and point inside the cage while in 31 the substituents at each nitrogen atom and the nitrogen atoms are situated in one plane.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Phenazin-5(10H)-yls, 4Parts 1-3: Ref.. 10-Ethylphenazin-5(10H)-yl · H2O: Crystal Structure, Magnetic Susceptibility and Intermolecular π-π Interactions (Pimerization)Dedicated to Professor Rolf Gleiter on the occasion of his 60th birthday. (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1867-1870 
    Details
    ISSN: 0947-3440
    Keywords: Phenazin-5(10H)-yl radicals ; Radical pairs ; π-π-Interactions ; Pimerization ; Dimer absorption ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unit cell of 10-ethylphenazin-5(10H)yl · H2O consists of eight phenazin-5(10H)-yls that are arranged in four independent radical pairs A-D. All pairs show close interplanar distances (3.28-3.36 Å). Furthermore, A, B, and D are characterized by short intermolecular contacts between atoms with significant spin populations. This is not valid for the pair C with the closest interplanar distance of 3.28 Å. Magnetic susceptibility measurements as a function of temperature indicate complete spin pairing (“pimerization”) between 20 and 100 K. Therefore, the radical pair C provides evidence that unspecific close interplanar contacts together with a reasonable overlap of the π systems are sufficient to lead to pimerization.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961121
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  • 4
    Electronic Resource
    Electronic Resource
    Palladium-Catalyzed Synthesis of Alkynylated 1,4:5,8:11,14:15,18-Tetrasulfido[20]annulenes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 525-529 
    Details
    ISSN: 1434-193X
    Keywords: Tetrasulfido[20]annulenes ; Thiophenophanes ; Porphycenes ; Alkynes ; McMurry coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of tetraalkynylated tetrasulfido[20]annulenes 2a-d are described. Treatment of the corresponding brominated tetrasulfido[20]annulene 5a (easily available by McMurry coupling of the brominated 2,2′-bithiophene-5,5′-dicarbaldehydes, 3a) with various acetylenes in the presence of Pd(II) and Cu(I) in NH(iPr)2 yields acetylenic tetrasulfido[20]annulenes 2a-d.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    2,3-Dialkynyl-1,4-diazabuta-1,3-dienes as Novel π-Systems: Synthesis, Structure, and Electronic Properties (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 205-214 
    Details
    ISSN: 1434-193X
    Keywords: Alkynes ; Cyclic voltammetry ; Diazabutadienes ; Electronic structure ; UV/Vis spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The introduction of alkynyl groups into the 2,3-positions of the 1,4-diazabuta-1,3-diene (DAD) backbone succeeds along two complementary synthetic routes either by condensing triisopropylsilyl-terminated dialkynyl-1,2-diones with primary aromatic amines or by a palladium-mediated alkynylation of bis(imidoyl chlorides). X-ray crystallographic analyses of two dialkynyl DAD derivatives reveals their planar (E-s-trans-E) conformations in the solid state. However, the central CC bond of both DAD backbones investigated has a length of 1.491(2) Å, and is therefore too long to indicate efficient delocalization across the DAD core. The UV/Vis spectra of dialkynyl DADs demonstrate that their absorptions in comparison to those of non-alkynyl DADs are bathochromically shifted by more than 40 nm, thereby demonstrating the suitability of the title compounds for developing NIR chromophores. The electron absorption properties of differentially N,N′-disubstituted dialkynyl DADs gave no indication for a push-pull effect across the DAD skeleton and suggest the ynimine moiety as the active chromophore of dialkynyl DADs. The electrochemical properties of the title compounds were determined by cyclo- and steady state voltammetry and show that introducing alkynyl groups leads to more easily reducible DAD systems. Again, the perception of dialkynyl DADs as covalently linked, but electronically decoupled ynimine units is corroborated by the redox potential of a differentially N,N′-disubstituted dialkynyl DAD. Similar conclusions were drawn from semiempirical MO (PM3) calculations of dialkynyl DADs.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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