Polymeric molecular shuttles: Polypseudorotaxanes & polyrotaxanes based on viologen (paraquat) urethane backbones & bis(p-phenylene)-34-crown-10
摘要:
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 H-1 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 Delta H = -6.91 kcal/mol and Delta S = -22.9 eu for 13R. (C) 2014 Elsevier Ltd. All rights reserved.
Self-Assembly, Spectroscopic, and Electrochemical Properties of [<i>n</i>]Rotaxanes<sup>1</sup>
作者:Peter R. Ashton、Roberto Ballardini、Vincenzo Balzani、Martin Bělohradský、Maria Teresa Gandolfi、Douglas Philp、Luca Prodi、Françisco M. Raymo、Mark V. Reddington、Neil Spencer、J. Fraser Stoddart、Margherita Venturi、David J. Williams
DOI:10.1021/ja954334d
日期:1996.1.1
Synthetic approaches to self-assembling [n]rotaxanes incorporating pi-eleclron deficient bipyridinium-based dumbbell-shaped components and pi-electron rich hydroquinone-based macrocycles have been developed. In particular, the so-called slippage methodology relies upon the size complementarity of preformed macrocyclic and dumbbell-shaped components. The spontaneous self-assembly of these complementary components into a rotaxane in solution can be achieved under the influence of an appropriate amount of thermal energy. The absorption spectra, luminescence properties, and electrochemical behavior of the rotaxanes and their dumbbell-shaped components have been investigated and discussed on the basis of the behavior of their chromophoric and electroactive units. Charge-transfer and energy-transfer processes between specific chromophoric subunits and unusual correlations between the redox patterns of the various compounds have been evidenced and interpreted.