Synthesis, spectroscopic and electrochemical characterization and molecular structure of polypyridyl ruthenium complexes containing 4,4'-azobis(pyridine)

GASTON POURRIEUX; FLORENCIA FAGALDE; NÉSTOR E. KATZ; TEODOR PARELLA; JORDI BENET-BUCHHOLZ; ANTONI LLOBET

POLYHEDRON

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: ÁMSTERDAN; Año: 2008 vol. 27 p. 2990 - 2996

0277-5387

New coordination compounds of formulae: [Ru(trpy)(bpy)(4,4’-azpy)]2+, 1, [Ru(tpm)(bpy)(4,4’-azpy)]2+, 2, [(trpy)(bpy)Ru(4,4’-azpy)Ru(NH3)5]4+, 3, and [(trpy)(bpy)Ru(4,4’-azpy)Ru(bpy)(trpy)]4+, 5, with trpy = 2,2´:6´,2”-terpyridine, tpm = tris(1- pyrazolyl)methane), bpy = 2,2´-bipyridine and 4,4’-azpy = 4,4´-azobis(pyridine), have been synthesized as PF6 - salts and characterized by spectroscopic and electrochemical techniques. The structure of the cation [Ru(trpy)(bpy)(4,4’-azpy)]2+ has been determined by X-ray diffraction analysis, which reveals a trans-configuration of coordinated 4,4’-azpy and a packing structure that is based on extensive p-interactions within neighboring molecules. Upon controlled potential electrolysis of the dinuclear [RuII,RuII] complex 3, a stable [RuII, RuIII] mixed-valent species, 4, was detected. From spectral data and Gaussian deconvolution analysis of the intervalence transition in 4, a strong electronic interaction between both ruthenium centers is disclosed (HAB = 550 cm-1 ), pointing to possible applications of 4,4’-azpy as a conducting bridge in “molecular wires”