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  • 1
    Electronic Resource
    Electronic Resource
    Controlling Self-AssemblyFrom a lecture delivered by J. F. S. at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. This paper is Part 26 in the series “Molecular Meccano” for Part 25, see S. Menzer, A. J. P. White, D. J. Williams, M. Belohradsky, C. Hamers, F. M. Raymo, A. N. Shipway, J. F. Stoddart, Macromolecules, in press. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1933-1940 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; molecular recognition ; pseudorotaxanes ; supramolecular chemistry ; translational isomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a result of cooperative noncovalent bonding interactions (namely, π-π stacking, [CH…O] hydrogen bonding, and [CH…π] interactions) supramolecular complexes and mechanically interlocked molecular compounds - in particular pseudorotaxanes (precatenanes) and catenanes - self-assemble spontaneously from appropriate complementary components under thermodynamic and kinetic control, respectively. The stereoelectronic information imprinted in the components is crucial in controlling the extent of the formation of the complexes and compounds in the first place; moreover, it has a very significant influence on the relative orientations and motions of the components. In other words, the noncovalent bonding interactions - that is, the driving forces responsible for the self-assembly processes - live on inside the final superstructures and structures, governing both their thermodynamic and kinetic behavior in solution. In an unsymmetrical [2]catenane, for example, changing the constitutions of the aromatic rings or altering the nature of substituents attached to them can drive an equilibrium associated with translational isomerism in the direction of one of two or more possible isomers both in solution and in the solid state. Generally speaking, the slower the components in mechanically interlocked compounds like catenanes and rotaxanes move with respect to each other, the easier it is for them to self-assemble.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031208
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  • 2
    Electronic Resource
    Electronic Resource
    Self-Assembly of Novel [2]Catenanes and [2]Pseudorotaxanes Incorporating Thiacrown Ethers or Their Acyclic AnaloguesMolecular meccano, part 19; for part 18, see: M. Asakawa, P. R. Ashton, C. L. Brown, M. C. T. Fyfe, S. Menzer, D. Pasini, C. Schever, N. Spencer, J. F. Stoddart, A. J. P. White, D. J. Williams, Chem. Eur. J. 1997, 3, in press. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 772-787 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; molecular devices ; pseudorotaxanes ; self-assembly ; translational isomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of π electron rich macrocyclic polythioethers and their acyclic analogues have been synthesized in good yields. The association constants for the complexation of the π electron deficient bis(hexafluorophosphate) bipyridinium-based salt, paraquat, by these macrocycles, as well as those for the complexation of corresponding acyclic compounds by the bipyridinium-based tetracationic cyclophane, cyclobis(paraquat-p-phenylene), are significantly lower than those observed in the case of the “all-oxygen” analogues. Nonetheless, yields as high as 86% were recorded in the template-directed syntheses of [2]catenanes composed of cyclobis(paraquat-p-phenylene) and the macrocyclic polythioethers. Single-crystal X-ray crystallographic analyses of the [2]catenanes incorporating constitutionally unsymmetrical π electron rich macrocyclic polythioethers revealed that, in all cases, the dioxyaromatic units are located inside the cavity of the tetracationic cyclophane component in preference to the dithiaaromatic units. A similar selectivity was observed in solution by variable-temperature 1H NMR spectroscopy. However, inversion of the ratio between the two translational isomers of the two [2]catenanes bearing 1,5-dithi-anaphthalene, as one of their π electron rich ring systems, and either 1,4-dioxy-benzene or 1,5-dioxynaphthalene, as the other, occurs upon increasing the temperature from -30 to +30 πC. These [2]catenanes can be viewed as temperature-responsive molecular switches.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030518
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  • 3
    Electronic Resource
    Electronic Resource
    Anthracene-Containing [2]Rotaxanes: Synthesis, Spectroscopic, and Electrochemical Properties (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 591-602 
    Details
    ISSN: 1434-193X
    Keywords: Cyclophanes ; Molecular recognition ; Molecular shuttles ; Rotaxanes ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two dumbbell-shaped compounds (8 and 11), each composed of two polyether chains intercepted by a 1,4-dioxybenzene recognition site, terminated by tetraarylmethane-based stoppers, and emanating from a central 9,10- or a 2,6-dioxyanthracene unit, have been synthesized. Two [2]rotaxanes (9 · 4 PF6 and 12 · 4 PF6) have been prepared by interlocking these dumbbell-shaped compounds (8 and 11) with a bipyridinium-based tetracationic cyclophane (15 · 4 PF6) - namely, cyclobis(paraquat-p-phenylene). A [3]rotaxane (10 · 8 PF6) incorporating two cyclophane components (15 · 4 PF6) was also obtained when the 9,10-dioxyanthracene-containing dumbbell-shaped compound (8) incorporating two 1,4-dioxybenzene recognition sites was employed. The 1H-NMR spectroscopic investigation of the [2]rotaxanes (9 · 4 PF6 and 12 · 4PF6) revealed that the cyclophane component encircles one of the two 1,4-dioxybenzene recognition sites in the 9,10-dioxyanthracene-containing [2]rotaxane (9 · 4 PF6) and the 2,6-dioxyanthracene unit in the other [2]rotaxane (12 · 4 PF6). These structures have been confirmed by UV/Vis and electrochemical experiments. Comparison with the spectroscopic properties of simple model compounds shows the presence of electronic interactions which lead to (i) the occurrence of very efficient energy transfer processes in the dumbbell-shaped components and (ii) perturbations in the absorption spectra with appearance of two charge-transfer absorption bands and complete luminescence quenching in the [2]rotaxanes. For the 2,6-dioxyanthracene-containing [2]rotaxane (12 · 4 PF6), it has been demonstrated that the cyclophane can be displaced from the dioxyanthracene to the 1,4-dioxybenzene station upon electrochemical oxidation.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Template-Directed Syntheses, Spectroscopic Properties, and Electrochemical Behavior of [n]Catenanes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1121-1130 
    Details
    ISSN: 1434-193X
    Keywords: Catenanes ; Cyclophanes ; Electrochemistry ; Electronic spectroscopy ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Catenanes composed of two, three, five, or seven interlocked macrocycles have been synthesized in yields ranging from 1 to 30%. Their template-directed syntheses rely on a series of cooperative noncovalent bonding interactions between π-electron rich 1,5-dioxynaphthalene ring systems and π-electron deficient bipyridinium units which are incorporated within the macrocyclic components. The interlocked structure associated with one of the [3]catenanes was demonstrated unequivocally by single crystal X-ray analysis which also revealed the formation of polar stacks stabilized by intermolecular [π···π] interactions. The number of interlocked components of each catenane was determined by liquid secondary ion, matrix-assisted laser desorption ionization/time-of-flight, and/or electrospray mass spectrometries. The absorption spectra, emission spectra, and electrochemical properties of the macrocyclic components and of the catenanes have been investigated. Two kinds of charge-transfer absorption bands (intramolecular in the cyclophanes containing electron-donor and electron-acceptor units, intercomponent in the catenanes) have been found. Such charge-transfer excited states are responsible for the quenching of the potentially fluorescence units of the cyclophanes, and of the crown ethers in the catenanes. Charge-transfer electronic interactions are also evidenced by the electrochemical behavior. Correlations among the redox potentials of the various compounds are reported and discussed.
    Additional Material: 7 Ill.
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