title: Rotaxanes and pseudorotaxanes with Fe-, Pd- and Pt-containing axles. Molecular motion in the solid state and aggregation in solution.
abstract: This article reviews our recent studies on structure and properties of rotaxanes and pseudorotaxanes with Fe-, Pd- and Pt-containing complexes as the axle component. Electrochemical oxidation of ferrocenylmethylamine in the presence of a hydrogen radical precursor induces formal protonation of the amino group and produces a pseudorotaxane of the resulting ammonium species with a crown ether. Single crystals of the ferrocene-containing pseudorotaxane undergo a thermal crystalline phase transition accompanied by changes in the optical properties of the crystals. X-Ray crystallographic studies of the low- and high-temperature phases revealed different intermolecular interactions and orientations of the aromatic rings in the crystalline state depending on the temperature. End-capping of the ferrocene-containing [2]pseudorotaxane using a cross-metathesis reaction yields [2]rotaxane under mild conditions. A rotaxane having a platinum-carboxylate complex as its axle is converted into related organic and inorganic rotaxanes by partial dissociation of the Pt-O bond. An N-alkylbipyridinium forms [3]pseudorotaxane with alpha-cyclodextrin (alpha-CD), and it reacts with platinum and palladium complexes to form the corresponding [5]rotaxanes containing four alpha-cyclodextrin moieties. Complexes without alpha-CD components form micelles in aqueous solution, while the addition of alpha-CD causes degradation of the micelles and the formation of rotaxanes.
authors.affiliation: Chemical Resources Laboratory R1-3, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Suzaki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taira
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Osakada
authors.forename: Masaki
authors.initials: M
authors.lastname: Horie