| Abstract
| - The self-assembly and characterization of a range of chiralpseudorotaxanes has been explored usingchiroptical methods. The syntheses of (i) constitutionallyasymmetric acyclic hydroquinone-containingpolyethers and (ii) optically active hydroquinone-containing acyclicpolyethers, bearing pairs of methyl orisobutyl groups related to each other in aC2-symmetric manner within the polyetherbackbone, are described.The combination of (i) the tetracationic cyclophanecyclobis(paraquat-p-phenylene)tetrakis(hexafluorophosphate), possessing a π-electron deficient cavity, and (ii) the linearnoncentrosymmetric acyclic polyethersproduces [2]pseudorotaxanes that have been characterized by1H NMR, UV/vis and circular dichroism (CD)spectroscopies in solution and by X-ray crystallography in the solidstate. The introduction of constitutionalasymmetry or chirality gives rise to a number of different geometriesfor the [2]pseudorotaxanes in both thesolution and solid states. In particular, CD-spectroscopicmeasurements on the optically active [2]pseudorotaxanes have shown thatdepending on the positions of theC2 symmetrically related chiralcentersin the polyether chains with respect to the hydroquinone ringsthechirality present in the π-electron richthreadlike guest can induce chirality that is associated with thesupramolecular structure as a whole, resultingin a chiral charge-transfer transition involving not only theπ-donors in the chiral guests but also the π-acceptorsin the achiral host.
|
