title: Dynamic chemical devices: modulation of photophysical properties by reversible, ion-triggered, and proton-fuelled nanomechanical shape-flipping molecular motions.
abstract: The terpy-derived (terpy=terpyridine) ligand 1 has an extended W shape in which the two appended photoactive pyrenyl groups are held apart. On binding of a zinc(II) ion with a terpy group, ligand 1 is converted into complex 2 whereby it adopts a U shape, thus stacking the aromatic units. This structural modification leads to a very pronounced change in photophysical properties: from a highly fluorescent free ligand to a very weakly emitting complex. The W/U structural switching can be reversibly induced by the addition of a competitive tren ligand, which binds and releases a zinc(II) ion under protonation/deprotonation cycles, thus leading to oscillations in light emission. Therefore, the present system performs periodic modulation of optical output through a nanomechanical shape-flipping motion, triggered by metal ion binding and fuelled by acid-base neutralisation energy. Overall, it represents an ion-triggered opto-mechanical supramolecular device.
authors.affiliation: Laboratoire de Chimie Supramoléculaire, ISIS, Université Louis Pasteur, 8, allée Gaspard Monge, BP 70028, 67083 Strasbourg Cedex, France.
authors.forename: Mihail
authors.initials: M
authors.lastname: Barboiu
authors.forename: Luca
authors.initials: L
authors.lastname: Prodi
authors.forename: Marco
authors.initials: M
authors.lastname: Montalti
authors.forename: Nelsi
authors.initials: N
authors.lastname: Zaccheroni
authors.forename: Nathalie
authors.initials: N
authors.lastname: Kyritsakas
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Lehn