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  • Organic Chemistry  (27)
  • Physical Chemistry  (1)
  • Polymer and Materials Science  (1)
  • Self-assembly  (1)
  • Supramolecular chemistry  (1)
  • molecular devices
  • 1990-1994  (18)
  • 1975-1979  (11)
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Keywords
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Crystal Structures of the Lanthanum(III), Europium(III), and Terbium(III) Cryptates of Tris(bipyridine) Macrobicyclic Ligands (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1163-1170 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of the LaIII, EuIII, and TbIII complexes of macrobicyclic [bpy.bpy.bpy] ligands, [La3+ ⊂ 1]3 Cl- ( = 3-La), [Tb3+ ⊂ 1]3 Cl- ( = 3-Tb), and [Eu3+ ⊂ 2]3 C1- ( = 3-Eu), have been determined. They confirm the cryptate nature of these species, the cations being bound to the eight N-sites of the ligand. The macrobicycle presents two open faces, thus allowing additional coordination of two species, Cl- ions or H2O molecules, to the bound cations. These data provide structural support for the photophysical studies of the luminescent properties of the EuIII and TbIII cryptates, which indicated residual coordination of H2O molecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740603
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  • 2
    Electronic Resource
    Electronic Resource
    Channel-Type Molecular Structures. Part 2Part 1: [1b].. Synthesis of Bouquet-Shaped Molecules Based on a β-Cyclodextrin Core (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 791-812 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new series of channel-type molecules presenting the features of potential transmembrane structures is described. They result from the grafting of amphiphilic side chains on a β-cyclodextrin derivative 3 that constitutes the organizing core. They belong to the ‘bouquet’ family (B). Compounds bearing poly(oxyethylene) side chains, BCDo16 and 17, and their polymethylene analogues BCDC18 and 19, were synthesized. The properties investigated emphasize the suitability of such molecules to be incorporated into lipid bilayer membranes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750315
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  • 3
    Electronic Resource
    Electronic Resource
    Caro-Cryptands: Tris-carotenoid macrobicyclic ligands-synthesis, crystal structure, and dinuclear copper(I) complexes (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 1069-1077 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tris-carotenoid macrobicycles 1 and 2 were obtained in good yields in a one-step macrobicyclisation condensation between the tripode N(CH2CH2NH2)3 and the polyolefinic dialdehydes 5 and 6. They form dinuclear cryptates by complexation of two CuI ions. The crystal structure of the tris-carotenoid compound 2 confirms that it contains three parallel polyolefinic strands. These substances may formally be considered as prototypes of molecular ‘cables’ formed by three electron-conducting molecular wires.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750410
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  • 4
    Electronic Resource
    Electronic Resource
    Stereoelectronic Properties, Stereospecificity and Stabilization of α-Seleno Carbanions. An ab initio StudyStereoelectronic Effects, Part 6; Part 5, see [2]. (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 1239-1246 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio study of α-seleno carbanions show that they are subject to appreciable polarization and stereoelectronic effects. Like in α-thia carbanions, the equatorial e forms are more stable than the axial a forms, one of the stabilizing contributions being the conformation dependent (C-lone pair, σ* Se—Z) interaction. The carbanion stabilizing effect of the α-Se atom is about 3 kcal/mol larger than that of the sulfur analog. As in the case of the sulfur no specific effect of the d orbitals is found.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600413
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  • 5
    Electronic Resource
    Electronic Resource
    Stereoelectronic Properties of Tetrahedral Species Derived from Carbonyl Groups. Ab initio study of aminodihydroxymethane, CH(OH)2NH2, a model tetrahedral intermediate in amide hydrolysis (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 1274-1286 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio theoretical study of all fifteen fully staggered conformations of aminodihydroxymethane, CH(OH)2NH2 has been performed. Optimization of the C—O and C—N bond lengths, population analyses and orbital localisation reveal the presence of marked conformation dependent stereoelectronic effects which influence bond lengths and overlap populations. These effects may be parametrized as a function of number and nature of antiperiplanar (app) oriented electronic lone pairs (1p) and polar bonds. In a Y—C—X fragment an app orientation between a lone pair on Y and the C—X bond increases the length and weakens the C—X bond, shortens and strengthens the C—Y bond. Thus a C—X (X = O, N) bond of CH(OH)2NH2 is longest and weakest when: (i) it is app to two vicinal lp's; (ii) the X 1p's are not app to a vicinal polar bond; (iii) the conformation of the molecule has as many axially oriented lp's as possible. Results (i) and (ii) agree with a simple hyperconjugation picture involving interaction between an electronic 1p and an app oriented antibonding bond orbital σ* (C—X). Bond properties, relative energies and effects on reactivity of the tetrahedral species are discussed, as well as their relations to experimental results on the cleavage of tetrahedral intermediates and to enzyme catalysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610410
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of the Copper(II) Complex of a Chiral Bis(dihydrooxazole) Ligand (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1-6 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bridged bis(dihydrooxazole) compound (-)-2 and its silylated derivative (-)-3 have been synthesised as building blocks for chiral ligands. The complex of (-)-3 with CuII has been obtained, and its crystal structure has been determined. The CuII ion is bound to two deprotonated ligands in a twisted tetracoordinated geometry.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740103
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and Properties of Sodium and Europium(III) Cryptates Incorporating the 2,2′-Bipyridine 1,1′-Dioxide and 3,3′-Biisoquinoline 2,2′-Dioxide Units (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 572-578 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sodium and europium cryptates of the new macrobicyclic ligands 2 and 3 incorporating the 2,2′-bipyri dine 1,1′-dioxide and 3,3′-biisoquinoline 2,2′-dioxide units, respectively, have been prepared. The EuIII complexes present characteristic 1H-NMR spectra, showing large shifts, and are strongly luminescent in aqueous solution. These markedly improved luminescent properties, compared to the europium cryptate of the parent macrobicyclic ligand 1, may be ascribed at least in part to a better shielding of the bound cation by the N-oxide sites.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740314
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  • 8
    Electronic Resource
    Electronic Resource
    Photo-Cleavable Cryptands: Synthesis and Structure (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 671-681 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four photo-cleavable ligands 1-4 of the macrobicyclic-cryptand type have been synthesized by introducing a photo-sensitive 2-nitrobenzyl- or 4,5-dimethoxy-2-nitrobenzyl-ether bond into one of the bridges. These compounds are expected to retain the selective binding features of the parent cryptands and to allow the photolytically induced release of alkali ions in aqueous solution. The crystal structures of the ligand 5-(2-nitro-phenyl)-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (3) and of its KSCN complex 13 have been determined. They are analogous to those of the corresponding parent species, confirming the macrobicyclic geometry and the cryptate nature of the complex. Spectroscopic properties are reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740402
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  • 9
    Electronic Resource
    Electronic Resource
    [M(bpy)3] (M = Fe, Ru, Os): New Crystalline Materials from the reductive electrocrystallization of [M(bpy)3](PF6)2 (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1222-1228 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reductive electrocrystallization at a constant current density (11.0-11.5 μA/cm2) of millimolar solutions of [M(bpy)3](PF6)2, where M = Fe, Ru, or Os, and bpy = 2,2′-bipyridine in acetonitrile containing 0.1M Bu4NPF6 results in the formation of dark crystals on the Pt cathode. The crystals grow as long, thin, and shiny needles having a hexagonal cross section of 0.1-0.5 mm in diameter. Combustion microanalyses results are consistent with the composition for [Fe(bpy)3], [Ru(bpy)3], and [Os(bpy)3]. In addition, the chromophores are conserved, as confirmed by recording both the electronic and the 1H-NMR spectra after reoxidation of the electrocrystals in humid air. The spectra are identical to those for authentic samples of [Fe(bpy)3]2+, [Ru(bpy)3]2+, and [Os(bpy)3]2+. A ratio of 2.0 ± 0.1 e-/molecule is observed upon completion of the controlled potential electrolysis of a solution of [M(bpy)3]2+, which results in the precipitation of a dark solid and the almost complete fading of the color of the original solution. Unexpectedly, the crystals do not exhibit an ESR signal. These data indicate the formation of novel materials, crystalline [Fe(bpy)3], [Ru(bpy)3], and [Os(bpy)3].
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770504
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and Metal-Binding Properties of Polybipyridine Ligands Derived from Acyclic and Macrocyclic Polyamines (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1149-1162 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic procedures have been developed for the preparation of ligands bearing two to six pendent, unsubstituted or substituted 2, 2′-bipyridine groups attached to acyclic (tripode, tetrapode) and macrocyclic (triazanonade-cane, cyclam, hexacyclen, bis(bipyrido)hexaazamacrocycle) polyamines. Ligands 1-5 have been obtained in high yield by condensation of 6-(bromomethyl)-2, 2′-bipyridine (9b) with the corresponding amines in the presence of NaOH, H2O, and MeOH. Ligands 6-8 have been prepared in good yield by condensation of 9b or the di- or tetrasubstituted mono (bromomethyl) bipyridine 10b or 11b, respectively, with the corresponding amines in the presence of Na2CO3 and MeCN. Ligand 1 forms hemi-cage complexes with RuII, FeI, CrII, and CrIII cations and trinuclear complexes with [RuCl2(bpy)2] and [ReCl(CO)5]. Tetrapode 2 and hexapode 4 gave tetranuclear and dinuclear complexes, respectively, by reaction with Fe11 salts. These complexes possess a variety of interesting physical and chemical properties.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730502
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