53914-95-7Relevant academic research and scientific papers
Polymeric molecular shuttles: Polypseudorotaxanes & polyrotaxanes based on viologen (paraquat) urethane backbones & bis(p-phenylene)-34-crown-10
Gibson, Harry W.,Shen, Ya Xi,Bheda, Mukesh C.,Gong, Caiguo
, p. 3202 - 3211 (2014)
Reaction of di(p-isocyanatophenyl)methane (MDI, 4) with N,N′-di(2-hydroxyethyl)- (1b) or N,N′-di[2-(2′-hydroxyethoxy) ethyl]-4,4′-bipyridinium di(hexafluorophosphate) (1e) and other diols [oligo(ethylene glycol)s and poly(tetramethylene oxide)s] in the presence of bis(p-phenylene)-34-crown-10 (2) afforded polyurethane (pseudo)rotaxanes as statistical (7P or 7R) and segmented analogs 10P (P = pseudorotaxane, R = rotaxane). In 7R a bulky alcohol was incorporated at the chain ends and in 13R a bulky diol as in-chain units to form polyrotaxanes and preclude the possibility of dethreading. The crown ether 2 in 10P and 13R was shown by 1H NMR spectroscopy to be shuttling between the viologen (paraquat) and urethane sites; in DMSO the crown ether prefers the urethane site, probably because of H-bonding with the N-H moieties and complexation of the pyridinium site by the dipolar solvent, while in acetone at low temperatures the viologen site is preferred by the crown ether, with ΔH = -6.91 kcal/mol and ΔS = -22.9 eu for 13R.
Proton ionizable 1H-1,2,4-triazole π-electron deficient cyclophanes as hosts and in [2]catenanes
Ramos, Susana,Alcalde, Ermitas,Fraser Stoddart,White, Andrew J. P.,Williams, David J.,Perez-Garcia, Lluisa
body text, p. 300 - 317 (2009/06/21)
The incorporation of proton ionizable moieties, such as 1H-1,2,4-triazole rings, within cyclophanes and π-donor/π-acceptor [2]catenanes is explored as a tool of inducing chemical switchability through either the inherent prototropic tautomerism or chemica
Conformational interconversions in [2]catenanes containing a wide rigid bis(p-benzyl)methyl spacer
Halterman, Ronald L.,Pan, Xingang,Martyn, David E.,Moore, Jason L.,Long, Andrew T.
, p. 6454 - 6458 (2008/02/10)
(Figure Presented) The conformational interconversions of four [2]catenanes (1-4) containing a dibenzo-34-crown-10 ether (BPP34C10) interlocked with rings containing two 4,4′-dipyridiniums tethered by 1,3-bis(ethyloxy)-phenyl and bis(p-benzyl)methyl spacers have been studied by VT 1H NMR spectroscopy. Symmetrically placed blocking groups on thickened tethers enabled either pathway for circumrotation of the BPP34C10 between isoenergetic sites to be blocked. On the basis of chemical shifts of the BPP34C10, its internal p-hydroquinone forms π-π-stacking interactions with only one 4,4′-dipyridinium ring at a time. The activation barrier for migration along either open tether was approximately 11.5 kcal/mol. This study demonstrates an ability to select the pathway for conformational interconversions in these [2]catenanes containing the rigid bis(p-benzyl)methyl tether and the lowering the barrier for interconversion through destabilization of the ground state structures.
The slipping approach to self-assembling [n]rotaxanes
Asakawa, Masumi,Ashton, Peter R.,Ballardini, Roberto,Balzani, Vincenzo,Bělohradsky, Martin,Gandolfi, Maria Teresa,Kocian, Oldrich,Prodi, Luca,Raymo, Fran?isco M.,Stoddart, J. Fraser,Venturi, Margherita
, p. 302 - 310 (2007/10/03)
A synthetic approach - namely slippage - to self-assembling [n]rotaxanes incorporating π-electron deficient bipyridinium-based dumbbell-shaped components and π-electron-rich hydroquinone- and/or dioxynaphthalene-based macrocyclic polyether components has been developed. The kinetics of rotaxane formation by the slipping procedure were investigated by absorption UV-visible and 1H-NMR spectroscopies in a range of temperatures and solvents, varying systematically the size of both the stoppers and the macrocyclic components. As expected, the rate constants for these processes are affected by the size complementarity between macrocycles and stoppers. Furthermore, the enthalpic and entropic contributions to the free energies of activation associated with the slippage and the effect of solvent polarity upon the outcome of these processes have been evaluated. In addition, the spectroscopic and electrochemical properties of some of the rotaxanes are presented and discussed with reference to the properties of their chromophoric and electroactive units.
From p-dimethoxybenzene to crown-benzenophanes, 4: Cation-complexing properties of Bis(p-phenylene-34-crown-10) - A structural and spectrophotometric study
Marquis, Damien,Greiving, Helmut,Desvergne, Jean-Pierre,Lahrahar, Nacer,Marsau, Pierre,Hopf, Henning,Bouas-Laurent, Henri
, p. 97 - 106 (2007/10/03)
The title compound 2, an electron-rich macrocyclic paracyclophane of the coronand type, known to form a charge-transfer complex with paraquat, was found to encapsulate strontium cations and to bind to magnesium cations. X-ray analysis revealed that 2 forms a 2:1 (metal/substrate) complex with Sr(ClO4)2, in which the two benzene rings weakly overlap, whereas in the single crystals grown from Mg(ClO4)2, the metal cation prefers to lie outside the coronand (1:1 stoichiometry). In acetonitrile solution, cations were observed to trigger an hypsochromic shift of the UV absorption spectra, proportional to their size and charge density. The stoichiometries and binding constants were also determined by UV absorption titration in acetonitrile using the LETAGROP-SPEFO program for several monovalent and divalent cations. For Na+, Ca2+, and Sr2+, 1:1 and 2:1 complexes were shown to be formed. In the free ligand, a weak interaction between the benzene rings was detected by fluorescence decay kinetic analysis, indicating the presence of two conformer populations within the nanosecond time scale. In solution, metal cations neither induce detectable excimer formation nor seem to have a strong influence on the fluorescence emission spectra, except a heavy atom quenching with Sr2+and Ba2+, in contrast to the effect observed in absorption. However, Sr2+ and Mg2+induce a clear hypsochromic shift in the single crystal fluorescence spectra. Compound 2 was prepared by a new and efficient route which is compared to the previous procedures. VCH Verlagsgesellschaft mbH, 1997.
Controlling catenations, properties and relative ring-component movements in catenanes with aromatic fluorine substituents
Ballardini, Roberto,Balzani, Vincenzo,Credi, Alberto,Brown, Christopher L.,Gillard, Richard E.,Montalti, Marco,Philp, Douglas,Stoddart, J. Fraser,Venturi, Margherita,White, Andrew J. P.,Williams, Brian J.,Williams, David J.
, p. 12503 - 12513 (2007/10/03)
Four new fluorine-containing macrocyclic polyethers based on bis-p- phenylene-34-crown-10 have been synthesized and subsequently catenated, separately, with cyclobis(paraquat-p-phenylene). The efficiencies of the catenations are strongly influenced by the aromatic ring templates in the macrocyclic polyethers. Incorporation of fluorine atom substituents into one of the hydroquinone rings in bis-p-phenylene-34-crown-10 had only a small effect on the percentage yields, whereas employing bis-p-phenylene-34-crown- 10 derivatives, in which both hydroquinone rings have been at least partially fluorinated, resulted in a dramatic decrease in catenation yields. In [2]catenanes incorporating macrocyclic polyethers containing one hydroquinone and one fluorinated hydroquinone ring, in both the solution (1H and 19F NMR, and UV-vis spectroscopies, electrochemical studies and molecular modeling) and solid (X-ray crystallography and molecular modeling) states, by far the major translational isomers observed were the ones with the hydroquinone ring located 'inside' the cavity of the tetracationic cyclophane. The diminished strength of the noncovalent interactions arising as a result of aromatic fluorine substituents is also reflected in the rates of the movements of the two ring components (dynamic NMR spectroscopy). As well as their electron-withdrawing effect, the fluorine substituents have a pronounced effect (UV-vis spectroscopy, electrochemical studies and molecular modeling) on the geometry of the ArO-CH2 bonds within the (fluorinated) hydroquinone rings.
Azobenzene-Based Photoswitchable Catenanes
Bauer, Martin,Mueller, Walter Manfred,Mueller, Ute,Rissanen, Kari,Voegtle, Fritz
, p. 649 - 656 (2007/10/02)
Four catenanes (1-4) and the corresponding tetracationic monocycles 5-8 are synthesized.X-ray structural analyses allow a prediction of the mobility (circumrotation) of the "interlocked" rings in the catenanes. which is proven by 1H-NMR spectroscopy.An unexpected order in the crystal packing of 6 is demonstrated. (E/Z) isomerization in one ring influences the second ring of 1-4 and inversely.An existing obstacle inside the cavity of the switchable macrocycle can block this isomerization completely. - Key Words: Catenanes / Interlocked rings / Mechanical bond / Photoswitches
Molecular meccano. 2. Self-assembly of [n]catenanes
Amabilino, David B.,Ashton, Peter R.,Brown, Christopher L.,Córdova, Emilio,Godínez, Luis A.,Goodnow, Timothy T.,Kaifer, Angel E.,Newton, Simon P.,Pietraszkiewicz, Marek,Philp, Douglas,Raymo, Fran?isco M.,Reder, Anatoli S.,Rutland, Marcus T.,Slawin, Alexandra M. Z.,Spencer, Neil,Stoddart, J. Fraser,Williams, David J.
, p. 1271 - 1293 (2007/10/02)
The mutual molecular recognition between different structural components in large rings has led to the template-directed synthesis of a wide range of catenanes composed of from two to five interlocked rings. The molecular self-assembly processes rely upon the recognition between (i) π-electron rich and π-electron deficient aromatic units and (ii) hydrogen bond donors and acceptors, in the different components. In order to increase our knowledge of the factors involved in such molecular self-assembly processes, a homologous series of [2]catenanes has been constructed using macrocyclic polyethers of the bis(p-phenylene)-(3n+4)-crown-n (n = 9-14) type as templates for the formation of the tetracationic cyclophane, cyclobis(paraquat-p-phenylene). Increasing the size of the tetracationic cyclophane to cyclobis(paraquat-4,4′-bitolyl) allows the simultaneous entrapment of two hydroquinone ring-containing macrocyclic polyethers affording a series of [3]catenanes, and one [4]catenane incorporating a cyclic dimer of the expanded cyclophane and three bis(p-phenylene)-34-crown-10 components. By analogy, increasing the number of hydroquinone rings in the macrocyclic polyether permits the self-assembly of more than one tetracationic cyclophane around the templates present in the macrocyclic polyether. In this context, the template-directed synthesis of two [3]catenanes, incorporating two cyclobis(paraquat-p-phenylene) components and either (i) tris(p-phenylene)-51-crown-15 or (ii) tetrakis(p-phenylene)-68-crown-20, has been achieved and is reported. A combination of these two approaches has led to the successful self-assembly, in two steps, of a linear [4]catenane, together with a small amount of a [5]catenane. The creation of these intricate molecular compounds lends support to the contention that self-assembly is a viable paradigm for the construction of nanometer-scale molecular architectures incorporating a selection of simple components.
Slippage - an Alternative Method for assembling Rotaxanes
Ashton, Peter R.,Belohradsky, Martin,Philp, Douglas,Stoddart, J. Fraser
, p. 1269 - 1274 (2007/10/02)
The exploitation of size-complementarity between the macrocyclic component and the stoppers of the cumbbell component of a rotaxane, together with stabilising noncovalent bonding interactions that create a thermodynamic trap, have permitted the development of an alternative method, which can be termed slippage, for the syntheses of rotaxanes in good yields.
Molecular meccano. 1. [2]rotaxanes and a [2]catenane made to order
Anelli, Pier Lucio,Ashton, Peter R.,Ballardini, Roberto,Balzani, Vincenzo,Delgado, Milagros,Gandoffi, Maria Teresa,Goodnow, Timothy T.,Kaifer, Angel E.,Philp, Douglas,Pietraszkiewicz, Marek,Prodi, Luca,Reddington, Mark V.,Slawin, Alexandra M.Z.,Spencer, Neil,Fraser Stoddart,Vicent, Cristina,Williams, David J.
, p. 193 - 218 (2007/10/02)
A new synthetic strategy for the elaboration of supramolecular species and molecular compounds containing noncovalently interacting components is described, with the long-term objective of constructing highly ordered, wholly synthetic assemblies from readily available starting materials. These could serve as a basis for the future development of mechanoelectrical and photoelectrical communication systems and devices capable of storing and processing information. The approach was conceived against a background of a quarter of a century's experience in supramolecular, alias host-guest, chemistry. It is based on the use of irreversibly interlocked molecular systems that take the form of catenanes and rotaxanes. Such compounds are seen to be the ideal vehicles through which to transfer from supramolecular and host-guest chemistry the knowledge and experience gained from studying complexes between small chemical entities to very much larger molecular assemblies. Once we know how to interlock molecular components irreversibly and efficiently, we shall have a very much clearer idea on how to intertwine related polymer chains reversibly. A number of template-directed syntheses of [2]rotaxanes and a [2]catenane is discussed. They illustrate that there are inherently simple ways of making apparently complex unnatural products from appropriate substrates without the need for reagent control or catalysis. The noncovalent bonding interactions that are used to self-assemble the 1:1 complexes, which serve as precursors to the rotaxanes and the catenane, as well as to the [2]rotaxanes and the [2]catenane themselves, "live on" in their structures and superstructures after the self-assembly process is complete. A variety of methods, including X-ray crystallography, fast atom bombardment mass spectrometry, ultra violet-visible, luminescence, nuclear magnetic resonance, and electron spin resonance spectroscopies, and electrochemistry, demonstrate the high structural order that is incorporated into these new molecular assemblies in both the solid and solution states.
