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  • catenanes  (12)
  • Template-directed synthesis  (8)
  • pseudorotaxanes  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    X-ray Crystallographic Studies on the Noncovalent Syntheses of Supermolecules (1999)
    Springer
    Structural chemistry 10 (1999), S. 243-259 
    Details
    ISSN: 1572-9001
    Keywords: Noncovalent interactions ; pseudorotaxanes ; self-assembly ; solid-state structures ; supramolecular chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An approach to the supramolecular syntheses of discrete multicomponent aggregates of noncovalently bound molecules, i.e., supermolecules, is described. This approach involved the careful analysis of X-ray crystal structures so as to permit a gradual increase in superstructural complexity. Many elaborate supermolecules were synthesized noncovalently from dialkylammonium-containing cations and crown ethers, following the initial observation that the dibenzylammonium ion threads through dibenzo[24]crown-8 to generate a singly stranded, singly encircled [2]pseudorotaxane, principally as a result of $$[{\text{N}}^{\text{ + }} - {\text{H}} \cdot \cdot \cdot {\text{O}}]$$ and $$[{\text{C}} - {\text{H}} \cdot \cdot \cdot {\text{O}}]$$ hydrogen bond formation. The scope of the fundamental recognition motif obtained from this initial observation was then broadened, through the use of thread-like ions with multiple dialkylammonium centers and/or larger crown ethers, so that multiply stranded and/or multiply encircled pseudorotaxanes could be prepared. Cations bearing both dialkylammonium and crown ether recognition sites were also used for the nocovalent synthesis of a discrete daisy chain supermacrocycle and the basic recognition motif was combined with other motifs for the production of a wide range of novel superarchitectures. As a greater understanding of the noncovalent interactions governing the self-assembly of the complex superarchitectures was acquired, new protocols for the noncovalent syntheses of doubly docked pseudorotaxanes and interwoven supramolecular bundles, including a supramolecular analogue of the photosynthetic special pair, were developed. The discovery that anions can play a prominent role in the solid-state self-assembly of some of the supermolecules was a valuable spinoff of the research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021844715425
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  • 2
    Electronic Resource
    Electronic Resource
    π-π INTERACTIONS IN SELF-ASSEMBLY (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 254-272 
    Details
    ISSN: 0894-3230
    Keywords: π-π interactions ; self-assembly ; catenanes ; cyclophanes ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The recent surge of interest in the control of molecular organization in both the solution state (i.e. self-assembly) and the solid state (i.e. crystal engineering) has led researchers to recognize increasingly the importance of weak non-covalent interactions. The design and synthesis of an efficient molecular construction set are dependent upon a very close interplay between x-ray crystallography and synthetic chemistry. π-π Stacking interactions between π-donors, such as hydroquinone, resorcinol or dioxynaphthalene residues, and π-accepting ring systems, such as bipyridinium or π-extended viologen units, can govern the self-assembly of a variety of complexes and interlocked molecular compounds in both the solid and solution states. Non-covalent bonding interactions (i.e. π-π interactions) can be considered as information vectors: they define and rule the self-assembly processes that lead to the formation of the desired molecular and supramolecular architectures, and thereafter they still govern the dynamic processes occurring within the self-assembled structures and superstructures. The manner in which such molecules and supermolecules can contribute to an understanding of non-covalent interactions at both structural and superstructural levels is described, with reference to numerous examples of self-assembly processes in synthesis, of dynamic processes in the solution state, and of the packing of molecules and molecular complexes in the solid state. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 31 Ill.
    Type of Medium: Electronic Resource
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Electrochemically Induced Molecular Motions in Pseudorotaxanes: A Case of Dual-Mode (Oxidative and Reductive) Dethreading (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1992-1996 
    Details
    ISSN: 0947-6539
    Keywords: cyclic voltammetry ; logic gates ; molecular devices ; pseudorotaxanes ; spectroelectrochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical and spectroscopic properties of a pseudorotaxane formed in acetonitrile solution by self-assembly of a wire-type electron donor based on the tetrathiafulvalene unit and the cyclobis(paraquat-p-phenylene) tetracationic electron acceptor have been investigated. We show that a) reversible dethreading/rethreading cycles of the pseudorotaxane can be performed by either oxidation and successive reduction of the electron-donor wire or reduction and successive oxidation of the electron-accepting tetracationic cyclophane, and b) because of this special behavior, the input (electrochemical)/output (absorption spectrum) characteristics of this molecular-level system correspond to those of an XNOR logic gate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031214
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  • 5
    Electronic Resource
    Electronic Resource
    Self-assembling [2]- and [3]rotaxanes from secondary dialkylammonium salts and crown ethersMolecular Meccano, Part 7: for Part 6; see the preceding paper in this issue (ref. [14]). (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 729-736 
    Details
    ISSN: 0947-6539
    Keywords: interlocking moleucles ; molecular recognition ; pseudorotaxanes ; rotaxanes ; template syntheses ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The self-assembly of three new rotaxanes - two [2]rotaxanes and a [3]rotaxane - formed by a “threading followed by stoppering” approach is described. These template-directed syntheses rely on the formation of pseudorotaxane intermediates, which self-assemble in solution from functionalized secondary dialkylammonium hexafluorophosphate threads and macrocyclic polyether rings (either dibenzo-[24]crown-8 or its asymmetric constitutional isomer). The stoppers - substituted 1,2,3-triazoles-were created by thermally allowed 1,3-dipolar cycloadditions between azido groups, which terminate the threads, and di-tert-butyl acetylenedicarboxylate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020615
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    High Yielding Template-Directed Syntheses of [2]Rotaxanes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2565-2571 
    Details
    ISSN: 1434-193X
    Keywords: Molecular recognition ; Rotaxanes ; Self-assembly ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three dumbbell-shaped compounds incorporating terminal triisopropylsilyl stoppers, connected to a central 1,5-dioxynaphthalene recognition site by [-CH2CH2O-]n spacers (n = 1-3), have been synthesized. These compounds have been employed as templates for the synthesis of [2]rotaxanes incorporating cyclobis(paraquat-p-phenylene) as the ring component. It was found that the length of the polyether chains of the templates influences the efficiencies of the template-directed syntheses. Rotaxane formation occurs only if n 〉 1 and, when n = 3 the corresponding [2]rotaxane can be isolated in a yield as high as 72 %. This remarkable yield is the highest ever obtained for the template-directed syntheses of [2]rotaxanes incorporating donor/acceptor interactions.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Pseudorotaxanes and Catenanes Containing a Redox-Active Unit Derived from Tetrathiafulvalene (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 985-994 
    Details
    ISSN: 1434-193X
    Keywords: Catenanes ; Molecular machines ; Pseudorotaxanes ; Template-directed synthesis ; Tetrathiafulvalenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Two bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene-containing acyclic polyethers and two macrocyclic polyethers, each incorporating one bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene unit and one p-phenylene ring, have been synthesized. The two acyclic polyethers are bound by cyclobis(paraquat-p-phenylene) with pseudorotaxane geometries in solution. The two macrocyclic polyethers have been mechanically interlocked with this tetracationic cyclophane to form [2]catenanes in a kinetically controlled self-assembly process. The X-ray crystallographic analysis of one of the two [2]catenanes and 1H-NMR-spectroscopic studies of both compounds showed that the p-phenylene ring of the macrocyclic polyether is located inside the cavity of the tetracationic cyclophane, while the bis(2-oxy-1,3-propylenedithio)tetrathiafulvalene unit resides alongside. The [2]pseudorotaxanes and [2]catenanes show broad bands around 780 nm, arising from the charge-transfer (CT) interaction between the electron-donor tetrathiafulvalene-(TTF-)type unit and the electron-acceptor units of the tetracationic cyclophane. 1H-NMR-spectroscopic studies have shown that the [2]pseudorotaxanes dissociate into their separate components upon oxidation of the TTF-type unit, as a result of disruption of the CT interaction and electrostatic repulsion between the tetracationic host and the newly formed monocationic guest. The subsequent reduction of the guest to its neutral state affords back the pseudorotaxane-type complex restoring the original equilibrium. The results obtained from electrochemical experiments are consistent with the reversible, redox-driven dethreading/rethreading process observed by 1H-NMR spectroscopy. Variable-temperature 1H-NMR-spectroscopic investigations have revealed two dynamic processes, both involving the relative movements of the mechanically interlocked components in the [2]catenanes. The two consecutive oxidation processes involving the TTF-type unit, observed electrochemically, are displaced toward more positive potentials compared with the free cyclic polyethers. The two reversible two-electron reduction processes, characteristic of free cyclobis(paraquat-p-phenylene), separate into four reversible one-electron processes because of the topological difference between the “inside” and “alongside” electron-acceptor units in the [2]catenane.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Main-Chain and Pendant Poly([2]catenane)s Incorporating Complementary π-Electron-Rich and -Deficient Components (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2109-2117 
    Details
    ISSN: 1434-193X
    Keywords: Catenanes ; Molecular recognition ; Polycatenanes ; Self-assembly ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A main-chain poly([2]catenane), incorporating an average of 25 repeating [2]catenane units and having an Mn value of 35 kg mol-1, was synthesized by the polyesterification of a [2]catenane monomer composed of a bipyridinium-based tetracationic cyclophane mechanically interlocked with a 1,5-dioxynaphthalene-based macrocyclic polyether. Similarly, two main-chain poly(bis[2]catenane)s, both incorporating an average of 15 repeating bis[2]catenane units and both having Mn values of 45 kg mol-1, were prepared by the copolymerizations of a bis[2]catenane monomer, possessing two hydroxymethyl functions with an appropriate bis(isocyanate). The same copolymerization was employed in order to produce a pendant poly([2]catenane), incorporating an average of 20 repeating [2]catenane units and having an Mn value of 27 kg mol-1, from a [2]catenane monomer possessing two hydroxymethyl groups on its macrocyclic polyether component.
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  • 10
    Electronic Resource
    Electronic Resource
    Template-Directed Synthesis of a Rotacatenane (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1295-1302 
    Details
    ISSN: 1434-193X
    Keywords: Catenanes ; Mechanically interlocked molecules ; Molecular recognition ; Rotaxanes ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A [2]catenane, able to bind π-electron-rich guests inside the cavity of one of its two macrocyclic components has been designed and synthesized using supramolecular assistance. This recognition motif has been exploited to template the formation of a so-called rotacatenane - i.e., a molecule composed of a dumbbell-shaped component threaded through the cavity of one of the two mechanically interlocked macrocyclic components of a [2]catenane. The structure of this [2]catenane, as well as that of a model [2]catenane, have been characterized unequivocally by single-crystal X-ray analyses. Furthermore, some of the co-conformational changes associated with these mechanically interlocked molecules in solution have been probed by variable-temperature 1H-NMR spectroscopy.
    Additional Material: 10 Ill.
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