New mono- and di-nuclear mixed complexes of cyanides and 2,3-bis(2′-pyridyl)pyrazine with ruthenium

The synthesis and spectroscopic, electrochemical and emissive properties,of a new mononuclear mixed complex, of formula. [Ru(dpp)(CN)(4)](2-) (dpp = 2,3-bis(2'-pyridyl)pyrazine are reported. The spectroscopic (IR, ,UV-visible, and emission) results demonstrate that dpp has a pi-acceptor capacity intermediate between bpy and bpz (bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine),when coordinated to ruthenium cyanides: The redox potential of the Ru-II/Ru-III couple and the observed luminiscence at room temperature imply its possible use as a photosensitizer. Since dpp has also the extra ability, when compared to bpy, to form supramolecular complexes, new dinuclear complexes with dpp bridging Ru(CN)(4)(n-) (n = 1,2) moieties can also be obtained. The corresponding mixed-valent complex, [(CN)(4)Ru-II(dpp)Ru-III(CN)(4)](3-), has the characteristics of a Class (II) species, as disclosed by the weak interaction between both metallic centres; (C) 1998 Elsevier Science Ltd. All rights reserved.