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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 749-754 
    ISSN: 0947-6539
    Keywords: clathrates ; host-guest chemistry ; hydrogen bonds ; macrocyclic ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterisation of eleven new macrocyclic ethers (up to 96-membered [6+6] gigantocycle) with well-defined cavities are described. Syntheses of the macrocycles M1-M7 were performed under high-dilution conditions. A “supramolecular” purification method was used for the small [2+2] macrocycles M3-M7, which separated selectively from the reaction mixture on recrystallisation from a dichloromethane/diethyl ether solution mixture. This proved to be an excellent method for purifying [2+2] macrocyclic ethers containing 1,1-diphenylmethane moieties, and the separation was nearly quantitative. Molecular inclusion of dichloromethane in the cavities of noncovalently bonded macrocyclic ethers M2-M5 was studied by X-ray diffraction in the solid state. Additionally, clathrate formation was found for macrocycles M1 (including diethyl ether), M2 (including water), M6 (including benzene) and M7 (including benzene).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1611-1615 
    ISSN: 0947-3440
    Keywords: Macrocycles ; Inclusion compounds ; Piperazines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New piperazine-based macrocycles with single small cavities were prepared by using high dilution technique. The inclusion of acetonitrile into the cavity (7, 8) or clathrate formation (3) was studied by 1H-NMR spectroscopy in solution and by X-ray diffraction in the crystalline state. The cycle 3 forms a molecular cleft, a molecular pocket, where the acetonitrile molecule is held by four weak N…H interactions reinforcing the clathrate formation. The cycles 7 and 8 contain a rigid cavity for an exact sterical fit with the methyl group of a linear compound like acetonitrile. The acetonitrile inclusion complex with 7 proved to be stable under normal conditions and was studied by means of thermogravimetry. It is stable up to 80°C and the breakdown is complete when the temperature is raised over 120°C. Solid-state IR studies show a shift of the cyano band of 5 cm-1 to smaller wave numbers when compared with free acetonitrile. The acetonitrile methyl group is shielded and in the 1H-NMR spectrum its signal is shifted to δ = 1.85.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1515-1519 
    ISSN: 0947-3440
    Keywords: Macrocycles ; Recognition ; Piperazines ; Self-assembly ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New large, up to 45-membered macrocycles were synthesised from piperazine and m- and p-2,6-bis(bromomethyl)xylene under high dilution conditions. X-ray structures of compounds 3a, 4a, 5a, and 8b were determined. Surprisingly, none of the macrocycles prepared showed any inclusion properties towards small guest molecules. Instead, the compounds were found to self-organize during the packing process into larger structures due to the complementary of the molecular skeletons. In the crystalline state 3a forms nets, where the macrocycles are bound by H—C—H…N interactions to each other. 4a exits in a dimeric structure, which, in turn, further extends to a sheet structure. The positively charged phane 8b (di-dihydrochloride salt) adopts a chair-chair conformation, confirming that protonation of the N atoms does not change the conformation.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. e216-e217 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: (Cyclohexylmethyloxymethyl)(1H-imidazol-4-iomethyl)-(S)-ammonium dichloride, C13H25N3O+·2Cl−, and (4-bromobenzyl)(1H-imidazol-4-iomethyl)-(S)-ammonium dichloride, C13H18BrN3O+·2Cl−, are model compounds with different biological activities for evaluation of the histamine H3-receptor activation mechanism. Both title compounds occur in almost similar extended conformations.
    Type of Medium: Electronic Resource
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