Spectral and electrochemical properties of the diastereoisomeric forms of azobis(2-pyridine)-bridged diruthenium species

A series of dinuclear complexes of ruthenium(II) have been synthesized in which α-azodiimines {such as azobis(2-pyridine), apy, and azobis(4-methyl-2-pyridine), mapy} act as the bridge and 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (Me2bpy) as the terminal ligands. The diastereoisomeric forms of each species {ΔΛ (meso) and ΔΔ/ΛΛ (rac)} have been separated by cation-exchange chromatography and characterized by 1H-NMR spectroscopy. Electronic spectral and electrochemical studies show there to be differences in inter-metal communication between the diastereoisomeric forms in each case. Comparison of the spectroelectrochemical behavior of the range of complexes has allowed unequivocal assignment of the site of the successive reduction processes observed in dinuclear complexes of this type