Complexes dinucléaires Ruthénium-cyanamides : composés modèles pour l'étude de la communication électronique à longue distance

Abstract : The electronic communication in ruthenium dinuclear complexes can be characterized either by the electronic coupling parameter Vab in mixed-valent systems (RuII-RuIII) or by the magnetic coupling parameter J in homovalent paramagnetic systems (RuIII-RuIII). The objective of this work was to obtain a family of compounds with different metal-metal distances and to measure the electronic and magnetic interactions in order to establish a potential correlation between J and Vab.
A first family of dinuclear complexes [{Ru(tpy)(acac)}2(µ-L)] (where tpy = 2,2'-6',2''-terpyridine, acac = acetylacetonate and L is a symmetrical phenylcyanamide bridging ligand) was synthesized but solubility problems were encountered.
A new family of complexes [{Ru(tpy)(thd)}2(µ-L)] (where thd- = 2,2,6,6-tetramethyl-3,5-heptanedionate), more soluble owing to the presence of tert-butyl groups, was thus synthesized using modern coupling methods. Concerning the shortest complex of this new family, electrochemical, spectroscopic, magnetic and crystallographic studies, completed with DFT calculations, highlighted the non-innocence of the 1,4-dicyanamidobenzene bridging ligand. Indeed, this ligand is oxidized before the two ruthenium (II) ions. For the four other complexes, the metal-metal distance of which varies between 16.0 and 25.1 Å, the mixed-valent (RuII-RuIII) and homovalent paramagnetic (RuIII-RuIII) forms were generated electrochemically. The electronic and magnetic coupling parameters were determined by UV-Vis spectroscopy and by variable-temperature EPR studies respectively. As expected, we found that these two parameters decay exponentially with the metal-metal distance. However, the relation we observed between these parameters differs from the theoretical predictions.
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Muriel Fabre. Complexes dinucléaires Ruthénium-cyanamides : composés modèles pour l'étude de la communication électronique à longue distance. Autre. Université Paul Sabatier - Toulouse III, 2006. Français. ⟨tel-00171709⟩

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