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  • Template-directed synthesis  (8)
  • pseudorotaxanes  (8)
  • Self-assembly  (5)
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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
    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.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular Meccano, 27.Part 26: R. E. Gillard, F. M. Raymo, J. F. Stoddart, Chem. Eur. J., in press. A Template-directed Synthesis of a Molecular Trefoil Knot (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2485-2494 
    Details
    ISSN: 0947-3440
    Keywords: Crown compounds ; Molecular knots ; Self-assembly ; Supramolecular chemistry ; Template-directed synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A design logic for the self-assembly of a molecular trefoil knot and of its isomeric trivial knot is described. The approach relies on the formation of a double-stranded supramolecular complex between an acyclic π-electron rich 1,5-di-oxynaphthalene-based polyether and an acyclic π-electron deficient bipyridinium-based tetracation. The reversible complexation of the two acyclic complementary components in solution is followed by the irreversible formation of covalent bonds connecting the termini of these two precursors within the supramolecular complex, affording both a trefoil knot and a trivial knot, though only in extremely low yields. The isomers were separated by preparative high-performance liquid chromatography and characterized by liquid secondary ion mass spectrometry which revealed the binding of up to two ammonium ions in the case of only one of the two isomers - namely, the trivial knot. In addition, we have performed binding studies between some model acyclic and macrocyclic 1,5-dioxynaphthalene-based polyethers and the bipyridinium based precursor of the knots. One of the complexes was also characterized in the solid state by X-ray crystallography which revealed the formation of a [2]pseudorotaxane in the solid state.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971210
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  • 4
    Electronic Resource
    Electronic Resource
    Pseudorotaxanes formed between secondary dialkylammonium salts and crown ethers“Molecular Meccano”, Part 6: for Part 5, see ref. [45e]. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 709-728 
    Details
    ISSN: 0947-6539
    Keywords: crown ethers ; dialkylammonium salts ; hydrogen bonding ; molecular recognition ; pseudorotaxanes ; self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A very simple self-assembling system, which produces inclusion complexes with pseudorotaxane geometries, is described. The self-assembly of eight pseudorotaxanes with a range of stoichiometries-1:1, 1:2, 2:1, and 2:2 (host:guest)-has been achieved. These pseudorotaxanes self-assemble from readily available components-well-known crown ethers, such as dibenzo[24]crown-8 and bis-p-phenylene[34]crown-10, and secondary dialkylammonium hexafluorophosphate salts, such as (PhCH2)2NH+2PF-6 and (nBu)2NH+2PF-6-and have been characterized not only in the solid state, but also in solution and in the “gas phase”. The pseudorotaxanes are stabilized largely by hydrogen-bonding interactions and, in some instances, by aryl-aryl interactions.
    Additional Material: 40 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020614
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Enantioselective Discrimination in the Self-Assembly of [2]Pseudorotaxanes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 983-986 
    Details
    ISSN: 1434-193X
    Keywords: Chirality ; Host-guest chemistry ; Enantioselective receptors ; CD spectroscopy ; Self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combination of (i) an optically active, axially chiral π-electron-deficient tetracationic cyclophane derivative of cyclobis(paraquat-p-phenylene), in which both of the p-phenylene spacers have been replaced by axially-chiral 3,3′-disubstituted binaphthol spacers, and (ii) enantiomeric, π-electron-rich substrates, in which a hydroquinone ring is inserted into the polyether backbone terminated by carboxyl groups and substituted in a C2-symmetric manner by two methyl groups, thus creating two equivalent chiral centers in the substrate, produces in solution 1:1 complexes in which the π-electron-rich substrates are inserted into the π-electron-deficient cavities of the cyclophanes in a pseudorotaxane-like manner. The differences in the free energies of complexation for (RR) and (SS) enantiomers of the π-electron-rich substrates span the range from 0.1 to 0.7 kcal mol-1. Chiral recognition becomes more effective the closer the chiral centers are to the hydroquinone templating unit. CD spectroscopy reveals that the different modes of binding of the enantiomeric substrates by the axially chiral tetracationic cyclophane are not accompanied by drastically different core geometries for the [2]pseudorotaxanes. Thus, the chirality of the complex is governed primarily by the properties of the rigid receptor. The combination of the D2 symmetry of the receptor with the C2 symmetry of the substrates has been found to be particularly effective, considering that the chiral centers on the substrates are located on polyether chains which possess a high degree of conformational freedom.
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