Using Redox-Active π Bridging Ligand as a Control Switch of Intramolecular Magnetic Interactions
Résumé
Intramolecular magnetic interactions in the dinuclear complexes [(tpy)Ni(tphz)Ni(tpy)] n+ (n=4, 3 and 2; tpy: terpyridine; tphz: tetrapyridophenazine) were tailored by changing the oxidation state of the pyrazine-based bridging ligand. While its neutral form mediates a weak antiferromagnetic (AF) coupling between the two S=1 Ni(II), its reduced form, tphz •-, promotes a remarkably large ferromag-netic exchange of +214(5)K with Ni(II) spins. Reducing twice the bridging ligand affords weak Ni-Ni interactions, in marked contrast to the Co(II) analogue. Those experimental results, supported by a careful examination of the involved orbitals, provide a clear understanding of the factors which govern strength and sign of the magnetic exchange through an aromatic bridging ligand, a prerequisite for the rational design of strongly coupled molecular systems and high T C molecule-based magnets.
Domaines
Matériaux| Origine | Fichiers produits par l'(les) auteur(s) |
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