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Construction of One-Dimensional Multicomponent Molecular Arrays: Control of Electronic and Molecular Motions

Authors

  • Jean-Paul Collin,

    1. Laboratoire de Chimie Organo-Minérale, UA 422 au CNRS, Institut de Chimie, Université Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg
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  • Pablo Gaviña,

    1. Laboratoire de Chimie Organo-Minérale, UA 422 au CNRS, Institut de Chimie, Université Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg
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  • Valérie Heitz,

    1. Laboratoire de Chimie Organo-Minérale, UA 422 au CNRS, Institut de Chimie, Université Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg
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  • Jean-Pierre Sauvage


Abstract

Transition metals are powerful three-dimensional templates, which can gather various functionalized ligands and orient them in a precise fashion so that complex multicomponent molecular systems can be obtained without constructing covalently-assembled edifices. The compounds thus prepared exhibit precise chemical or physical functions, which are governed by the design of the system. The construction of one-dimensional molecules around ruthenium(II) or osmium(II), using rigid ligands attached to the desired electroactive species, leads to systems that are able to undergo charge separation after photonic excitation. In other related compounds, a ruthenium(II)-based chromophore is, for example, connected to an osmium(II) complex by means of rod-like bridging ligand, thereby ensuring strict control over the Ru···Os distance. By tuning the length and the electronic properties of the bridge, one can control the efficiency of the electronic energy transfer between the two chromophores. In particular, the use of a bis-cyclometallating ligand is very conducive to energy transfer and allows the observation of this process up to a Ru…Os distance of ≈20 Å. By combining the building blocks of these inorganic systems with appropriate porphyrins, long-range (centre-to-centre distance between the donor and the acceptor porphyrins ≈30 Å) and relatively long-lived photoinduced charge separation has been demonstrated. Finally, with copper(I) as the template, compounds of the rotaxane family are obtained, which consist of a coordinating ring threaded by a string-like component. If this acyclic fragment is end-functionalized by two bulky stoppering groups and if it incorporates two different coordination sites (a bi- and a terdentate chelate site), novel dynamic properties are observed. The movement of a given fragment of the molecule is triggered by changing the metal oxidation state. This one-dimensional motion of the ring along the string on which it is threaded is controlled by redox manipulation, resulting in a primitive molecular machine.

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