ELECTROCHEMISTRY OF [(RU(BPY)2)2BPM](PF6)4 - COMPLETE ASSIGNMENT OF INDIVIDUAL REDUCTION STEPS

[(Ru(bpy)2)2bpm]4+ (1) was shown to undergo 14 one-electron processes at the electrode-two Ru-based oxidations and twelve ligand-based reductions. Unlike thc case of other mononuclear Ru-bpm complexes, in 1 the bridging bpm ligand is reduced in two one-electron steps to the dianion before reduction of the terminal bpy. After the first stage of reduction of all the bpy ligands, the next reduction is one involving the second LUMO of mu-bpm. The reduction of bpm is completed by a second one-electron process at more negative potentials only after all bpy ligands undergo reduction to bpy2-. The products of the reduction up to the 3- species are fairly stable; however, the products of more negative processes undergo decomposition within the time scale of the CV method. All electron repulsion interactions, as reflected in the DELTA-E-degrees values, were identified, and it was shown that the mu-bpm ligand transmits electronic effects in unreduced as well as in reduced form. The fact that the first two electrons are accepted by bpm before the reduction of bpy is discussed in terms of fully symmetrical coordination of bpm.