ELECTROCHEMISTRY OF COVALENTLY LINKED SUPRAMOLECULAR SPECIES - REDOX SERIES OF THE TRINUCLEAR COMPLEX NC-RU(BPY)2-CN-RU(DCE-BPY)2-NC-RU(BPY)2-CN2+ (BPY = 2,2'-BIPYRIDINE DCE-BPY = 5,5'-DICARBOXYETHYL-BPY)

The electrochemical behaviour of the trinuclear complex NC-RuII(bpy)2-RuII(DCE-bpy)2-NC-RuII(bpy)2-CN2+, where bpy = 2,2'-bipyridine and DCE-bpy = 5,5'-dicarboxyethyl-bpy, was studied in acetonitrile and in N,N-dimethylformamide. Because of the high number of oxidizable and reducible centres, this trinuclear complex gives rise to a very extended redox series formed by 14 redox steps, three of which are due to one-electron reversible oxidations of Ru(II) to Ru(III), while the remaining 11 can be ascribed to one-electron reversible reductions of bipyridine ligands. Such behaviour, for the reduction processes, is observed only at low temperature (-54-degrees-C) and at a sufficiently high sweep rate (10 V s-1). Comparison between the behaviour of this complex and the previously studied trinuclear species NC-RuII(bpy)2-CN-RuII(bpy)2-NC-RuII(bpy)2-CN2+ has allowed us to confirm the previous assignment of the localization of the electron density changes in the individual redox steps. Moreover, additional spectroscopic evidence is provided that the more easily oxidizable Ru(II) centre in such species is the central Ru(II) atom.