title: A Switchable Hybrid [2]-Catenane Based on Transition Metal Complexation and π-Electron Donor-Acceptor Interactions.
abstract: A bimodal [2]-catenane has been synthesized via a copper(I) templated synthesis. The compound contains both a transition metal coordination site and a set of π-electron rich and π-electron deficient aromatic units suitable for the formation of acceptor-donor complexes. Each constituent ring is thus different from the other, and the organic backbone can adopt two favored contrasting orientations by circumrotation of one ring within the other:  (i) in the metal complex mode, each dpp unit (dpp = 2,9-diphenyl-1,10-phenanthroline) is entwined about the other, while a cationic species is complexed in the coordination site thus created; (ii) in the organic π-electron acceptor-donor complex mode, the dpp fragments are remote from one another, and the π-electron rich and π-electron deficient units stack to form a complex. The conversion of one binding mode to the other implies complete topographical rearrangement of the molecule. It can be triggered by adding or removing the cation center (Cu+, Li+, or H+), bonded to the dpp-containing complexing site. Interestingly, this switching process can be easily monitored by1H NMR, since it involves drastic relative orientational changes. It can also be evidenced by electronic spectroscopy. In particular, the proton-driven rearrangement reactions lead to significant changes in the absorption spectrum, which correspond to the appearance (by deprotonation) and disappearance (by protonation of the dpp) of a charge transfer band (around 470 nm) resulting from the π-electron donor-acceptor noncovalent interaction.
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: David B
authors.initials: DB
authors.lastname: Amabilino
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: Christiane O
authors.initials: CO
authors.lastname: Dietrich-Buchecker
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: Aude
authors.initials: A
authors.lastname: Livoreil
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: Lluïsa
authors.initials: L
authors.lastname: Pérez-García
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Sauvage
authors.affiliation: Contribution from the Laboratoire de Chimie Organo-Minérale, URA 422 du CNRS, Institut Le Bel, Université Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France, and The School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart