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  • Articles  (115)
  • General Chemistry  (63)
  • Molecular Sequence Data  (52)
  • Astrophysics
  • SOLAR PHYSICS
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  • 11
    Electronic Resource
    Electronic Resource
    Cyclobis(paraquat-4,4′-biphenylene)-an organic molecular square(Molecular Meccano), Part 8: for Part 7, see P. R. Ashton, P. T. Glink, J. F. Stoddart, P. A. Tasker, A. J. P. White, D. J. Williams, Chem. Eur. J. 1996, 2, 729-736. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 877-893 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; second-sphere coordination ; self-assembly ; template syntheses ; topological stereoisomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Template-directed syntheses of cyclobis(paraquat-4,4′-biphenylene) (1)- a Molecular square-have been achieved by use of π-electron-rich macrocyclic hydroquinone-based and acyclic ferrocene-based templates. In particular, the use of a polyether-disubstituted ferrocene derivative as a template permits synthesis of 1 (which is accessible only in very low yields without templates) on a preparative scale. Furthermore, the use of a macrocyclic hydroquinone-based polyether template in corporating an ester function in one polyether chain-an (oriented) macrocycle-affords a 1 : 1 mixture of two topologically stereoisomeric [3]catenanes. Ester hydrolysis of the π-electron-rich macrocyclic components mechanically interlocked with 1 within the catenated structures releases the tetracationic cyclophane in quantitative yield as a result of the degradation of the [3]catenanes. The molecular square has been characterized by X-ray crystallography, FAB mass spectrometry, 1H NMR and 13C NMR spectroscopies, and elemental analysis. The binding properties of 1 and of the smaller cyclophane cyclobis(paraquat-p-phenylene) toward a series of π-electronrich guests have also been investigated with the above techniques and UV/VIS spectroscopy. The self-assembly of the resulting supramolecular complexes in solution and in the solid state is driven mainly by π-π stacking interactions and hydrogen-bonding interactions, as well as by edge-to-face T-type interactions. In particular, the complexation of ferrocene or a ferrocene-based derivative within the cavity of 1 suggests the possibility of constructing functioning ferrocene-based molecular and supramolecular devices that can be controlled electrochemically in the form of catenanes, rotaxanes, and pseudorotaxanes.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020718
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  • 12
    Electronic Resource
    Electronic Resource
    Linear, Divergent Molecular Receptors - Subtle Effects of Transition Metal Coordination Geometry (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 823-826 
    Details
    ISSN: 1434-1948
    Keywords: Thiacalixarene ; Trimetallic sandwich ; Cobalt ; Zinc ; Divergent receptors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction between deprotonated p-tert-butyltetrathiacalix[4]arene and CoII or ZnII under strictly defined conditions leads to the formation of sandwich species in which a trimetallic unit is held between two opposed, divergently oriented, staggered O- and S-bound calixarene ligands in the cone conformation. Despite the isomorphous nature of the crystalline compounds, there is a subtle difference in the coordination of CoII and ZnII, presumably related to the differences in metal radius and electron configuration combined with structural restrictions imposed by the calixarene framework, in that whereas all three Co atoms may be considered six-coordinate (and approximately octahedral), only two of the Zn atoms appear so, the third being five-coordinate and more nearly trigonal bipyramidal in its coordination geometry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Molecular Meccano, 48Probing Co-Conformational Changes in Chiral [2]Rotaxanes by 1H-NMR Spectroscopy (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 899-908 
    Details
    ISSN: 1434-193X
    Keywords: Co-conformation ; Molecular recognition ; Planar chirality ; Rotaxanes ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The template-directed syntheses of three [2]rotaxanes possessing either chiral centers or elements of planar chirality, in one of their two mechanically interlocked components, have been realized and their solid-state structures have been analyzed by X-ray crystallography. In one instance, an enantiomerically pure dumbbell-shaped component incorporating a 1,5-dioxynaphthalene recognition site and two (1R,2S,5R)-menthyl stoppers was employed to template the formation of the achiral tetracationic cyclophane, cyclobis(paraquat-p-phenylene). The resulting enantiomerically pure [2]rotaxane was isolated in a yield of 55%. In the other two instances, an achiral 1,5-dioxynaphthalene-based dumbbell-shaped component was employed to template the formation of bipyridinium-based cyclophanes possessing either one or two elements of planar chirality. The resulting [2]rotaxane, possessing one element of planar chirality, was isolated as a racemate in a yield of 24%. The related [2]rotaxane, possessing two elements of planar chirality, was isolated as a mixture of a meso form and an enantiomeric pair in an overall yield of 28%. The 1H-NMR-spectroscopic analysis of this mixture revealed a diastereoisomeric ratio of 4:1. A degenerate co-conformational change was identified by variable-temperature 1H-NMR spectroscopy in all [2]rotaxanes. The symmetry loss arising from the introduction of one or two elements of planar chirality enabled the elucidation of the mechanism of this dynamic process in two instances.
    Additional Material: 12 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Zur elektrophilen Substitution an Sechsring-HeteroaromatenNach Vorträgen in den Jahren 1964 und 1967 vor: „Heterocyclic Conference for College Teachers“, Bozeman, Montana; I.C.I. Petrochemical and Polymer Laboratory, Runcorn; Los Angeles, Groningen, Warschau, Berlin, Rom und Exeter. (1967)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 79 (1967), S. 629-636 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Im folgenden wird ein Überblick über die noch recht lückenhaften quantitativen Ergebnisse zur elektrophilen Substitution an Heteroaromaten gegeben. In erster Linie tut not, mehr über die in die Reaktion eintretenden Spezies selbst zu wissen; in zweiter Linie interessiert, inwieweit das Heteroatom den aromatischen Ring - verglichen mit dem entsprechenden Benzolderivat - aktiviert oder desaktiviert. Hat man genügend experimentelle Daten, so läßt sich hoffen, diese mit Hilfe von MO-Berechnungen oder im Sinn einer Hammettschen Substituentensystematik zu ordnen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19670791402
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  • 15
    Electronic Resource
    Electronic Resource
    Chemisch erzeugte angeregte Zustände (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 86 (1974), S. 292-307 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bei vielen chemischen Reaktionen entstehen organische Moleküle in elektronisch angeregten Zuständen. Solche chemisch erzeugten angeregten Zustände stimmen (mit einer Ausnahme) mit den angeregten Zuständen überein, die durch Lichtabsorption entstehen, und sie unterliegen den molekularen Umwandlungen, die man von solchen Zuständen erwartet („Photochemie ohne Licht“). Die angeregten Moleküle können auch in Energieübertragungs-Experimenten verwendet werden. Dieser Fortschrittsbericht befaßt sich mit der chemischen Erzeugung angeregter Zustände, ihren chemischen Reaktionen sowie mit der Rolle, die chemisch erzeugte angeregte Zustände möglicherweise in der Biologie spielen.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19740860803
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  • 16
    Electronic Resource
    Electronic Resource
    Symposium über nicht-silicatische Keramik 11. bis 13. Juli 1962, Stoke-on-Trent. Herstellung und Eigenschaften hitzebeständiger Uranverbindungen (1962)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 74 (1962), S. 879-879 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19620742130
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  • 17
    Electronic Resource
    Electronic Resource
    Gärungsröhrchen (1927)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 40 (1927), S. 1341-1341 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19270404517
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  • 18
    Electronic Resource
    Electronic Resource
    Self-Assembly and Self-Organization of Self-Recognizing Cyclophanes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 969-981 
    Details
    ISSN: 1434-193X
    Keywords: Crystal engineering ; Host-guest chemistry ; Nanotubes ; Sandwich complexes ; Self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis is presented of the different contributions that give rise to the packing observed in the crystal structures of a wide range of bipyridinium-based molecular assemblies and supramolecular arrays. It is demonstrated how the various interactions - electrostatic, van der Waals, and π-π interactions - that contribute to the solid-state arrangement of these molecules and supermolecules can be utilized in order to design a series of tetracationic cyclophanes that can potentially self-organize in a highly ordered way in the solid state by virtue of the fact that they contain π-electron donors as well as π-electron acceptors. The syntheses of these cyclophanes is outlined and the tunability of the self-assembly methodology in their construction is demonstrated. One of these tetracationic cyclophanes - comprising π-electron-rich hydroquinone rings and π-electron-deficient bipyridinium units - has been shown to pack as highly ordered two-dimensional, mosaic-like sheets in the solid state. Its dicationic precursor also forms extended π-π-stacked layers in the solid state. An analogous cyclophane - containing two π-electron-rich resorcinol rings in place of the two hydroquinone rings - forms, in the solid state, one-dimensional arrays wherein the component resorcinol rings interact through their parallel π-π stacking. It has also been established that the first of the aforementioned tetracationic cyclophanes forms a 1:1 adduct with ferrocene in both the solution and solid states. X-ray crystallography, performed on the 1:1 adduct, reveals that not only is the ferrocene molecule complexed in a π-π stacking sense within the tetracationic cyclophane, but the 1:1 adduct also packs in a manner that is remarkably similar to the supramolecular organization of the free cyclophane in the crystalline state.
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  • 19
    Electronic Resource
    Electronic Resource
    Simple Mechanical Molecular and Supramolecular Machines: Photochemical and Electrochemical Control of Switching Processes“Molecular Meccano”, Part 14: for Part 13, see D. B. Amabilino, P. R. Ashton, V. Balzani, C. L. Brown, A. Credi, J. M. J. Fréchet, J. W. Leon, F. M. Raymo, N. Spencer, J. F. Stoddart, M. Venturi, J. Am. Chem. Soc., in press. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 152-170 
    Details
    ISSN: 0947-6539
    Keywords: luminescence ; photochemistry ; redox chemistry ; self-assembly ; self-complexation ; template syntheses ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical control of a self-assembled supramolecular 1:1 pseudorotaxane (formed between a tetracationic cyclophane, namely the tetrachloride salt of cyclobis(paraquat-p-phenylene), and 1,5-bis[2-(2-(2-hydroxy)ethoxy)ethoxy]naphthalene) has been achieved in aqueous solution. The photochemical one-electron reduction of the cyclophane to the radical trication weakens the noncovalent bonding interactions between the cyclophane and the naphthalene guest - π-π interactions between the π-electron-rich and π-electron-poor aromatic systems, and hydrogen-bonding interactions between the acidic α-bipyridinium hydrogen atoms of the cyclophane and the polyether oxygen atoms of the naphthalene derivative - sufficiently to allow the guest to dethread from the cavity; the process can be monitored by the appearance of naphthalene fluorescence. The radical tricationic cyclophane can be oxidized back to the tetracation in the dark by allowing oxygen gas into the system. This reversible process is marked by the disappearance of naphthalene fluorescence as the molecule is recomplexed by the tetracationic cyclophane. This supramolecular system can be chemically modified such that the π-electron-rich unit, either a naphthalene derivative or a hydroquinone ring, and the tetracationic cyclophane are covalently linked. We have demonstrated that the π-electron-rich residue in this system is totally “self-complexed” by the cyclophane to which it is covalently attached. Additionally, the self-complexation can be switched “off” and “on” by electrochemical two-electron reductions and oxidations, respectively, of the tetracationic cyclophane component. Thus, we have achieved the construction of two switches at the nanoscale level, one driven by photons and the other by electrons.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030123
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  • 20
    Electronic Resource
    Electronic Resource
    Molecular and Supramolecular Synthesis with Dibenzofuran-Containing SystemsMolecular meccano, part 18; for Part 17, see D. B. Amabilino, P. R. Ashton, S. E. Boyd, M. Gómez-López, W. Hayes, J. F. J. Org. Chem. 1997, 62, 3062-3075. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1136-1150 
    Details
    ISSN: 0947-6539
    Keywords: crystal engineering ; dibenzofuran ; molecular quadrilaterals ; supra-molecular chemistry ; template synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The template-directed syntheses of two new tetracationic cyclophanes, cyclobis(paraquat-2,8-dibenzofuran) and cyclobis(paraquat-3,7-dibenzofuran), incorporating dibenzofuran subunits has been accomplished. Initially, the cyclophanes were self-assembled around a macrocyclic polyether template, bis-p-phenylene[34]crown-10 (BPP34C10), to form catenanes: the mechanical bond order of the catenane formed determined the requisite “amacrocyclic” templates for synthesis of the free cyclophane. X-ray crystallography shows that both of the cyclophanes possess rectangular covalent frameworks. Furthermore, these cyclophanes form self-assembled tapes in the solid state, since the dibenzofuran moieties have a tendency to associate with each other through crossed ∞-∞ stacks. The dibenzofuran-containing catenanes also form two-dimensional supramolecular arrays in the solid state on account of extended ∞-∞ stacking interactions. In addition, the serendipitous discovery of a plerotopic tecton (consisting of a dibenzofuran nucleus covalently linked from the 2- and 8-positions by methylene groups to 4,4′-pyridylpyridinium (hydrogen bond acceptor) and protonated bipyridinium (hydrogen bond donor) units) has been made. The tecton dimerizes in the solid state to form a supramolecular macrocycle, since its complementary hydrogen bonding sites are oriented in a horseshoelike fashion by the 2,8-disubstituted dibenzofuran unit. However, this superstructure is not retained in the 1:1 complex of the tecton with BPP34C10: cocrystallization of the tecton with this crown ether opens the macrocyclic two-component supermolecule to afford a hydrogen-bonded pseudopolyrotaxane.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030720
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