Synthesis and Photochemical Properties of New Polypyridyl Ruthenium(II) Tetrazolate Complexes

Over the past years, a wide range of nitrogen rich aromatic ligands have been employed in the design of mono and polynuclear ruthenium (II) or osmium (II) polypyridyl complexes. On the other hand, tetrazole compounds have been only marginally considered in such kind of chemistry. Thus, as the extension of some previous studies,[1] we have prepared several mono and dinuclear Ru(II) polypyridyl complexes containing various 5-substituted tetrazolate as mono-coordinated or chelating ligands. A complete survey of the main coordinative, electrochemical and structural features of these complexes will be discussed as well as some interesting results about their photochemical properties. In particular, unusually highly efficient red light emission was observed by performing electrogenerated chemiluminescence (ECL) experiments on the dinuclear species [(tpy)(bpy)Ru-N4CC6H4CN-Ru(bpy)(tpy)][PF6]3. In addition, since the introduction of thienyl units plays an important role in the design of promising ECL molecules and oxygen sensitizers, we are currently engaged in the synthesis of new polynuclear Ru(II) polypyridyl complexes containing thienyl-tetrazolate bridging ligands by the appropriate cross coupling reactions of the parent mononuclear compounds. [1] Palazzi, A.; Stagni, S. J. Organomet. Chem., 690, 2005, 2052; Vos, J.G.; Ward, M.D.; Duati, M.; Stagni, S.; Tasca, S.; Lynch, F.C.; Bohlen, H. Inorg. Chem., 42, 2003, 8377; Palazzi, A.; Stagni, S.; Monari, M.; Selva, S. J. Organomet. Chem., 669, 2003, 135; Palazzi, A.; Stagni, S.; Bordoni, S.; Monari, M.; Selva, S. Organometallics, 21, 2002, 3774;