A Diruthenium Complex of an N-Pyridyl-o-aminophenol Derivative: A Route to Mixed Valency.

An N-pyridyl-o-aminophenol derivative that stabilises mixed-valence states of ruthenium ions is disclosed. A diruthenium complex, [(L )Ru Cl ]⋅MeOH (1⋅MeOH) is successfully isolated, in which L is the o-iminobenzoquinone form of 2-[(3-nitropyridin-2-yl)amino]phenol (L H ). In 1, L oriented towards one ruthenium centre is a non-innocent NO-donor redox ligand, whereas another oriented towards another ruthenium centre is an innocent pyridine-donor redox ligand. Complex 1 is a diruthenium(II,III) mixed-valence complex, [Ru (L )(μ-Cl) Ru ], with a minor contribution from the diruthenium(III,III) state. [Ru (L )(μ-Cl) Ru ] contains L , which is the o-iminobenzosemiquinonate anion radical form of the ligand. Complexes 1 and 1 are diruthenium(II,II), [Ru (L )(μ-Cl) Ru ], and diruthenium(III,III), [Ru (L )(μ-Cl) Ru ], complexes, respectively, of L . Complex 1 is a diruthenium(II,II) complex of the o-iminobenzosemiquinonate anion radical (L ), [Ru (L )(μ-Cl) Ru ], with a minor contribution from the diruthenium(III,II) form, [Ru (L )(μ-Cl) Ru ]. Complex 1 is a diruthenium(III,IV) mixed-valence complex of L , [Ru (L )(μ-Cl) Ru ]. Complexes 1 and 1 exhibit inter-valence charge-transfer transitions at λ=1300 and 1370 nm, respectively.