Synthesis, spectroscopy and electrochemistry of a mu-oxo-triruthenium cluster containing a bridged bis(2,2 '-bipyridyl)ruthenium(II) moiety

A bridged cluster species of formula [Ru3O(CH3COO)(6)(py)(2)(4,4'-bpy)Ru(bp y)(2)(Cl)](PF6)(2) (py = pyridine, bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-b ipyridine) has been synthesized and characterized based on electronic and 2 D NMR spectroscopy, cyclic voltammetry and UV-Vis spectroelectrochemistry. The electronic spectra of the complex exhibit the characteristic MLCT band for the [Ru(bpy)(2)Cl](+) moiety at 489 nm, and a broad band at 692 nm ascr ibed to [Ru3O] internal core transitions. The complex exhibit a reversible multistep redox behavior in the range from - 1.5 to 2.5 V (SHE), consisting of five monoelectronic waves at - 1.31, - 1.06, 0.15, 1.17 and 2.09 V ascr ibed to [Ru3O] core redox processes, and at 0.98 V ascribed to the [Ru(bpy) (2)Cl] (+/+2) redox couple. Both Ru+2/+3 pair and [Ru3O](-1/0+1) processes are influenced significantly by the electronic interactions through the 4,4 '-bipyridine bridging ligand. (C) 2001 Elsevier Science B.V. All rights res erved.