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Complexes superstructurés mixtes Ru/Fe et Ru/Co à ligands polypyridinyles multitopiques : synthèses, caractérisations, propriétés rédox et photorédox.

Abstract : This work deals with the synthesis and physico-chemical study of heterobimetallic complexes bearing ruthenium(II)-tris-bipyridine units as photosensitizers covalently linked to a polypyridinic complex unit of iron (II) or cobalt (II), in order to investigate photoinduced electron transfer in such architectures.
With bis-bipyridine type ligands, we synthesized a serie of tetranuclear complexes formed by a central complex unit FeII-tris-bipyridine, covalently linked to three RuII-tris-bipyridine subunits. Examination of their photophysical properties revealed a partial energy transfer between FeII subunit and excited state of RuII subunit, RuII*. This energy transfer can be easily short-circuited in presence of an external irreversible electron acceptor by an electron transfer process, leading to formation of RuIII species able to oxidize FeII subunit. By using a heteroditopic bipyridine-terpyridine type ligand, new trinuclear complexes bearing a central unit of FeII or CoII bis-terpyridine complex linked to two RuII-tris-bipyridine subunits were synthesized. This ligand confers to these architectures a more linear structure. In the case of the iron complex, purely intramolecular energy transfer can be short-circuited too, by electron transfer in presence of an external irreversible electron acceptor leading to the complete oxidation of FeII subunit. In the case of the cobalt complex, the photocatalytic cycle we considered implies formation of RuIII species via an electron transfer between RuII* and CoIII (previously electrogenerated) as electron acceptor. Nevertheless this reaction is fairly slow because the external electron donor used to regenerate RuII does not display a convenient irreversibility to prevent back electron transfer between CoII and RuIII.
Finally, RuII and FeII electro- and photo-activable coordination polymers studies have been started. These types of polymers derive from the RuII and FeII trinuclear complex. They are obtained under soluble forms by the use of a heteroditopic bipyridine-bis-terpyridine type ligand, where the bipyridine part is complexed by RuII whereas addition of Fe2+ ions leads to the formation of polymers by a self-assembly process. Likewise RuII and FeII finished-dimension complex, photoinduced oxidation of FeII unit is possible even if its efficiency depends on the nature of the bridge between bipyridine and terpyridine units. Moreover, these polymers can be adsorbed as electroactive thin layers at the surface of an electrode (elaboration of modified electrodes) by a simple electrodeposition technique.
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Submitted on : Friday, December 7, 2007 - 6:26:16 PM
Last modification on : Friday, November 6, 2020 - 3:44:10 AM
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Jean Lombard. Complexes superstructurés mixtes Ru/Fe et Ru/Co à ligands polypyridinyles multitopiques : synthèses, caractérisations, propriétés rédox et photorédox.. Autre. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00194974⟩

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