title: Translational Isomerism in Some Two- and Three-Station [2]Rotaxanes.
abstract: The template-directed syntheses of three [2]rotaxanes are described. They all have dumbbell components, with both hydroquinone and resorcinol rings inserted into polyether chains terminated by tetraarylmethane stoppers, that become encircled during the key self-assembly processes by the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), with its two pi-electron deficient bipyridinium units. It has been demonstrated by low-temperature (1)H NMR spectroscopy that the pi-electron deficient tetracationic cyclophane has a remarkably high preference to reside around the hydroquinone ring in these molecular shuttles. This observation illustrates how a very small constitutional difference-hydroquinone versus resorcinol recognition sites-can lead to the overwhelming preference for one translational isomer over another in this particular range of [2]rotaxanes.
authors.affiliation: School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: David B.
authors.initials: DB
authors.lastname: Amabilino
authors.forename: Peter R.
authors.initials: PR
authors.lastname: Ashton
authors.forename: Sue E.
authors.initials: SE
authors.lastname: Boyd
authors.forename: Marcos
authors.initials: M
authors.lastname: Gómez-López
authors.forename: Wayne
authors.initials: W
authors.lastname: Hayes
authors.forename: J. Fraser
authors.initials: JF
authors.lastname: Stoddart