Ruthenium polypyridyl complexes containing the bischelating ligand 2,2′-azobispyridine. Synthesis, characterization and crystal structures

Three ruthenium polypyridyl compounds of structural formula [Ru(apy)(tpy)Ln−](ClO4)(2−n) (apy = 2,2′-azobispyridine; tpy = 2,2′:6′,2″-terpyridine; L = Cl, H2O, CH3CN) (1a–c) were synthesized and crystallized. These complexes were fully characterized by means of 1D and 2D 1H NMR spectroscopy, as well as mass spectrometry and elemental analysis. Although in theory two isomers are possible, i.e. the one in which the central N atom in tpy is trans to the azo N in apy and the one in which the former is trans to the pyridine N in apy, in all cases only the latter was observed. The molecular structures of the compounds were elucidated by single-crystal X-ray diffraction.