title: Solid-state characterization and photoinduced intramolecular electron transfer in a nanoconfined octacationic homo[2]catenane.
abstract: An octacationic homo[2]catenane comprised of two mechanically interlocked cyclobis(paraquat-p-phenylene) rings has been obtained from the oxidation of the septacationic monoradical with nitrosonium hexafluoroantimonate. The nanoconfinement of normally repulsive bipyridinium units results in the enforced π-overlap of eight positively charged pyridinium rings in a volume of <1.25 nm(3). In the solid state, the torsional angles around the C-C bonds between the four pairs of pyridinium rings range between 16 and 30°, while the π-π stacking distances between the bipyridinium units are extended for the inside pair and contracted for the pairs on the outside--a consequence of Coulombic repulsion between the inner bipyridinium subunits. In solution, irradiation of the [2]catenane at 275 nm results in electron transfer from one of the paraphenylene rings to the inner bipyridinium dimer, leading to the generation of a temporary mixed-valence state within the rigid and robust homo[2]catenane.
authors.affiliation: Department of Chemistry and ‡Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Barnes
authors.forename: Marco
authors.initials: M
authors.lastname: Frasconi
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Young
authors.forename: Nezar H
authors.initials: NH
authors.lastname: Khdary
authors.forename: Wei-Guang
authors.initials: WG
authors.lastname: Liu
authors.forename: Scott M
authors.initials: SM
authors.lastname: Dyar
authors.forename: Paul R
authors.initials: PR
authors.lastname: McGonigal
authors.forename: Ian C
authors.initials: IC
authors.lastname: Gibbs-Hall
authors.forename: Christian S
authors.initials: CS
authors.lastname: Diercks
authors.forename: Amy A
authors.initials: AA
authors.lastname: Sarjeant
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Stern
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart