title: Successive Translocation of the Rings in a [3]Rotaxane.
abstract: A [2]rotaxane, a [3]rotaxane and the corresponding thread containing two succinamide (succ) binding stations and a central redox-active pyromellitimide (pmi) station were studied. Infrared spectroelectrochemical experiments revealed the translocation of the macrocycle between the succinamide station and the electrochemically reduced pmi station (radical anion and dianion). Remarkably, in the [3]rotaxane, the rings can be selectively translocated. One-electron reduction leads to the translocation of one of the two macrocycles from the succinamide to the pyromellitimide station, whereas activation of the shuttle through two-electron reduction results in the translocation of both macrocycles: the dianion, due to its higher electron density and hence greater hydrogen-bond accepting affinity, is hydrogen bonded to both macrocycles. Systems with such an on-command contraction are known as molecular muscles. The relative strengths of the binding between the macrocycle and the imide anions could be estimated from the hydrogen-bond-induced shifts in the C=O stretching frequencies of hydrogen-bond accepting amide groups of the macrocycle.
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD, Amsterdam, The Netherlands.
authors.forename: Dhiredj C
authors.initials: DC
authors.lastname: Jagesar
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD, Amsterdam, The Netherlands.
authors.forename: Piet G
authors.initials: PG
authors.lastname: Wiering
authors.affiliation: School of Chemistry, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK.|EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.
authors.forename: Euan R
authors.identifier: 0000-0001-8177-6393
authors.initials: ER
authors.lastname: Kay
authors.affiliation: School of Chemistry, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK.|School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: David A
authors.identifier: 0000-0002-1202-4507
authors.initials: DA
authors.lastname: Leigh
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD, Amsterdam, The Netherlands. a.m.brouwer@uva.nl.
authors.forename: Albert M
authors.identifier: 0000-0002-1731-3869
authors.initials: AM
authors.lastname: Brouwer
keywords: IR spectroscopy; electrochemistry; molecular devices; reduction; rotaxanes