Synthesis and characterization of mono-, bi- and tetra-ruthenium(II) phenanthroline complexes with dipyrido(2,3-α;2′,3′-h)phenazine (dpop)

A series of coordination complexes, [(phen)(2)Ru(dpop)] (PF6)(2), [((phen)(2)Ru)(2)(dpop) ] (PF6)(4) and [((phen)(2)Ru(dpop))(3)Ru] (PF6)(8) (dpop = dipyrido(2,3-a; 2',3'-h)phenazine) were synthesized, and their properties characterized. Electronic absorption spectra display intense metal-to-ligand charge transfer absorptions in the visible spectrum at wavelengths longer than reported for similar complexes with other bridging ligands. Cyclic voltammograms show reversible waves associated with ruthenium oxidation and dpop reductions. The cyclic voltammogram of the tetra-ruthenium complex shows two sets of dpop reduction waves which are separated from the phen reductions. Electrolysis of the multi-ruthenium complexes produces mixed valent species that display absorptions in the near-IR associated with intervalence transfer (IT) transitions. Spectroelectrochemical data are presented and used to support transition assignments. (C) 1998 Elsevier Science S.A. All rights reserved.