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  • 1
    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.
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    A Novel Type of Isomerism in [3]CatenanesMolecular meccano, part 20; for part 19, see: M. Asakawa, P. R. Ashton, W. Dehaen, G. L'abbé, S. Menzer, J. Nouwen, F. M. Raymo, J. F. Stoddart, M. S. Tolley, S. Toppet, A. J. P. White, D. J. Williams, Chem. Eur. J. 1997, 3, 772. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 788-798 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; dynamics ; isomerization ; NMR spectroscopy ; self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The self-assembly of three [3]-catenanes based on a single tetracationic cyclophane - cyclobis(bipyridinium-1,4-di-ethoxybenzene) - with pairs of identical interlocked crown ethers - bis-p-phenyl-ene[34]crown-10, bis-1,5-dioxynaphthal-ene[38]crown-10, or tetrafluoro-p-phenyl-ene-p-phenylene[34]crown-10 - has been achieved in yields of 34, 31, and 33%, respectively. The solid-state structures of these [3]catenanes, determined by X-ray crystallography, are consistent with molecules having approximately C2h symmetry. In the solution state, the π-electron rich aromatic ring systems of the crown ether components, residing within the cavity of the tetracationic cyclophane, can adopt two different relative orientations, thus giving rise to two distinct isomeric forms possessing either C2h or D2 symmetries. Two dynamic processes have been characterized in the [3]catenane incorporating bis-1,5-dioxynaphthalene[38]-crown-10 macrocycles, by means of variable-temperature 1H NMR spectroscopy and subsequent lineshape analyses. The slower process is the exchange between C2h and D2 isomers, and the faster process is the rotation of the bipyridinium units of the cyclophane around their N=N axes. The evaluation of the free energies of activation at 298 K, which are, for the slower process, ca. 16 kcal mol-1, and for the faster one, ca. 14.5 kcal mol-1, has enabled us to propose a scenario in which the two included 1,5-dioxynaphthalene ring systems move continuously about the center of the cavity of the tetracationic cyclophane. A partial dissociation of one 1,5-dioxynaphthalene ring system allows the adjacent bipyridinium units to rotate about their long axes, whereas a complete dissociation is presumably necessary to allow a 1,5-dioxynaphthalene ring system to rotate about its O=O axis. The isomerism between the C2h and the D2 isomers of the [3]catenane incorporating the two bis-1,5-dioxynaphthalene[38]crown-10 rings is dependent upon 1) translational motions between the two crown ether rings and the central tetracationic cyclophane and 2) conformational changes within at least one of the two crown ether rings.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030519
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  • 6
    Electronic Resource
    Electronic Resource
    Axially Chiral Catenanes and π-Electron-Deficient Receptors“Molecular Meccano”, Part 16: for Part 15, see D. B. Amabilino, P. R. Ashton, S. E. Boyd, M. Gómez-López, W. Hayes, J. F. Stoddart, J. Org. Chem.1997, in press. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 463-481 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; chirality ; enantioselection ; receptors ; self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The design of a new class of chiral [2]catenanes is reported. The self-assembly of [2]catenanes comprising one or two 3,3′-bitolyl spacers in the π-electron-deficient component, and bis-p-phenylene-34-crown-10 (BPP 34 C 10) as the π-electron-rich component, is described. The X-ray crystal structures, together with solution-state dynamic 1H NMR spectroscopic studies, show that the degree of order characterizing the molecular structures is substantially different from that of the “parent” [2]-catenane, comprising cyclobis(paraquat-p-phenylene) and BPP34C 10. When appropriately substituted in their ortho positions, bitolyl compounds can support axial chirality: the self-assembly of axially chiral [2]catenanes, comprising one or two 3,3′-disubstituted-2,2′-dihydroxy-1,1′-binaphthyl spacers, has been achieved in good yields, showing that the introduction of the bulky, axially chiral spacer and the consequent distortion of the cavity of the π-electron-deficient component still permits good molecular recognition between the components leading to efficient catenane production. X-ray crystallography suggests that this recognition is driven by hydrogen bonding and π-π stacking interactions between the complementary subunits. The hydroxyl groups on the chiral spacer were further functionalized as benzoyl esters in a [2]catenane as well as in the tetracationic cyclophanes; that is, chemistry can be done on these catenanes. The chiral tetracationic cyclophanes exhibit good enantiomeric differentiation toward the D- and L-enantiomers of aromatic amino acids in water and their N-acetylated derivatives in organic solvents.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030319
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Catenated Cyclodextrins (1995)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 1 (1995), S. 33-55 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; cyclodextrins ; macrocycles ; orientational isomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel synthetic approach is described for the construction of catenanes in aqueous solution from a partially methylated cyclodextrin (CD)-namely, heptakis(2,6-di-O-methyl-β-cyclodextrin) (DM-β-CD)-and a range of substrate molecules that contain a hydrophobic central core in the form of a 4,4′-disubstituted biphenyl unit (usually bitolyl) carrying two hydrophilic polyether side chains terminated by primary amine functions. In water, the amphiphilic catenane precursors form 1:1 complexes with β-CD and DM-β-CD and 2:1 (guest: host) complexes with the larger γ-CD. Macrocyclizations of the biphenyl-containing substrates with aromatic diacid chlorides in aqueous solution and in the presence of DM-β-CD under Schotten-Baumann conditions afforded-in low yields-a range of [2]- and [3]catenanes. When a consitutionally asymmetrical diamine was employed as the substrate, orientational isomers of a [2]catenane were obtained. A [3]catenene incorporating a macrocyclic tetralactam was found to exist as a mixture of head-to-head and head-to-tail isomers, which could be separated by high pressure liquid chromatography and identified unambiguously by nuclear magnetic resonance spectroscopy. One of the [2]catenanes afforded good single crystals from which the solid state structure was determined by X-ray crystallography. Other techniques which aided the characterization of these novel compounds included ultraviolet/visible and luminescence spectroscopy, dynamic nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. Generally speaking, the catenated cyclodextrins are soluble in halogenated and aromatic hydrocarbons as well as in hydroxylic solvents. The existence of these new compounds gives us a unique insight into the nature of the noncovalent bonding interactions that cyclodextrins employ in binding substrate molecules.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19950010109
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  • 9
    Electronic Resource
    Electronic Resource
    Bis[2]catenanes and a bis[2]rotaxane-Model Compounds for Polymers with Mechanically Interlocked Components“Molecular Meccano”, Part 5: for Part 4, see P. R. Ashton, R. Ballardini, V. Balzani, A. Credi, M. T. Gandolfi, S. Menzer, L. Pérez-Garcia, L. Prodi, J. F. Stoddart, M. Venturi, A. J. P. White, D. J. Williams, J. Am. Chem. Soc. 995, 117, 11171-11197. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 31-44 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; polycatenanes ; polyrotaxanes ; rotaxanes ; self-assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The self-assembly of three bis[2]catenanes and a bis[2]rotaxane, by two complementary strategies, is reported. A synthetic route to derivatives of bis-para-phenylene[34]crown-10 (BPP34C10) and 1,5-naphtho-para-phenylene[36]-crown-10 (1/5NPP36C10) containing a fused five-membered ring with a secondary amine function is described. These intermediate N-allylimido macrocyclic polyethers undergo template-directed reactions with 1,1′-[1,4-phenylenebis-(methylene)]bis-4,4′-bipyridinium bis-(hexafluorophosphate) and 1,4-bis(bromo-methyl)benzene to produce [2]catenanes containing an N-allyl functionality. The N-allylimido macrocyclic polyethers have also been reduced and deprotected to afford macrocycles possessing a free NH group, which are then linked through a 4,4′-biphenyldicarbonyl spacer to produce bis(crown ether)s, in which each crown ether moiety has two recognition sites. These ditopic BPP34C10 and 1/5NPP36C10 derivatives are capable of sustaining self-assembly reactions at both recognition sites to yield bis[2]catenanes. The self-assembly of a complementary bis[2]catenane, in which two tetracationic cyclophanes are linked together with a flexible hexyl chain, has also been achieved by treating 1,1′-[1,4-phenylenebis(methylene)]bis-4,4′-bipyridinium bis-(hexafluorophosphate) with a compound containing two linked 1,4-bis(bromomethyl)benzene units in the presence of BPP34C10. Replacing BPP34C10 with a dumbbell-shaped compound containing a linear polyether unit intercepted by a naphthalene residue and terminated by two bulky adamantoyl groups has led to the self-assembly of a bis[2]rotaxane. The X-ray crystal structures of one of the catenanes and its associated crown ether component are reported, together with solution state dynamic 1H NMR spectroscopic studies, showing that there is substantial degree of order characterizing the molecular structure of the catenanes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020109
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  • 10
    Electronic Resource
    Electronic Resource
    Controlling Translational Isomerism in [2]CatenanesThis work was supported by the Engineering and Physical Sciences and Engineering Research Councial (UK). We thank the Ministerio de Educatión y Cienca (Spain) for a Fleming Postdoctoral Fellowship (to L. P.-G.). (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 571-574 
    Details
    ISSN: 0570-0833
    Keywords: catenanes ; crown ethers ; self-assembly ; translational isomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199505711
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