title: Dinuclear ruthenium bipyridine complexes with a bis(iminodioxolene)-meta-phenylene ligand: magnetic coupling and mixed valence character of the semiquinonato species.
abstract: The dinuclear bis-iminosemiquinonato [Ru(bpy)(2)(L)(2)Ru(bpy)(2)](PF(6))(2) complex where L is the deprotonated form of N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,3-phenylenediamine (H(4)L), has been synthesised. For comparison purposes, the mononuclear iminosemiquinonato [Ru(bpy)(2)L']PF(6) formed by the N-phenyl-o-aminophenol (H(2)L') was also investigated. Magnetic investigation evidences that the bis-semiquinonato species is characterised by a moderately strong ferromagnetic interaction (H=JS(1) x S(2), J=-85(5) cm(-1)). This result is the theoretically expected one and it is contrasting with the antiferromagnetic interaction observed in previously investigated complexes containing the same ligand. It is suggested that the different behaviour is determined by the different coordination requirements occurring in these complexes. The spectroelectrochemical analysis provides a clear evidence of the valence trapped character of the mono-semiquinonato forms of the ligand. The two mixed valence semiquinonato species containing the quinonato-semiquinonato and semiquinonato-catecholato bridging ligand can be described as class II, but show a significantly different electronic coupling. The electronic factors determining this behaviour are discussed.
authors.affiliation: Dipartimento di Chimica dell'Universita di Siena, Via Aldo Moro, 53100 Siena, Italy.
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Fabrizi De Biani
authors.forename: Andrea
authors.initials: A
authors.lastname: Dei
authors.forename: Claudio
authors.initials: C
authors.lastname: Sangregorio
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Sorace
mesh_terms: D000627:Aminophenols / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004583:Electrons; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D010655:Phenylenediamines / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000627:Aminophenols; D008024:Ligands; D009942:Organometallic Compounds; D010655:Phenylenediamines; D011725:Pyridines; D011809:Quinones; C116897:iminoquinone; D012428:Ruthenium