title: Induction of motion in a synthetic molecular machine: effect of tuning the driving force.
abstract: Rotaxane molecular shuttles were studied in which a tetralactam macrocyclic ring moves between a succinamide station and a second station in which the structure is varied. Station 2 in all cases is an aromatic imide, which is a poor hydrogen-bond acceptor in the neutral form, but a strong one when reduced with one or two electrons. When the charge density on the hydrogen-bond-accepting carbonyl groups in station 2 is reduced by changing a naphthalimide into a naphthalene diimide radical anion, the shuttling rate changes only slightly. When station 2 is a pyromellitimide radical anion, however, the shuttling rate is significantly reduced. This implies that the shuttling rate is not only determined by the initial unbinding of the ring from the first station, as previously supposed. An alternative reaction mechanism is proposed in which the ring binds to both stations in the transition state.
authors.affiliation: Van 't Hoff Institute for Molecular Science, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jacob
authors.initials: J
authors.lastname: Baggerman
authors.forename: Natalia
authors.initials: N
authors.lastname: Haraszkiewicz
authors.forename: Piet G
authors.initials: PG
authors.lastname: Wiering
authors.forename: Giulia
authors.initials: G
authors.lastname: Fioravanti
authors.forename: Massimo
authors.initials: M
authors.lastname: Marcaccio
authors.forename: Francesco
authors.initials: F
authors.lastname: Paolucci
authors.forename: Euan R
authors.initials: ER
authors.lastname: Kay
authors.forename: David A
authors.initials: DA
authors.lastname: Leigh
authors.forename: Albert M
authors.initials: AM
authors.lastname: Brouwer
mesh_terms: D000577:Amides / Q000737:chemistry*; D000838:Anions; D004563:Electrochemistry; D004583:Electrons; D006860:Hydrogen Bonding; D007094:Imides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009038:Motion; D009281:Naphthalenes / Q000737:chemistry; D043862:Rotaxanes / Q000138:chemical synthesis* / Q000737:chemistry; D013386:Succinates / Q000737:chemistry*
chemical_list: D000577:Amides; D000838:Anions; D007094:Imides; D009281:Naphthalenes; D043862:Rotaxanes; D013386:Succinates; C542131:naphthalenediimide; C011116:succinamide