We have synthesized highly viscous, room-temperature, molten salts by associating various Ru(NH3)(5)L cations (L = 4,4'-bipyridine, pyrazine, pyridine, 3-chloropyridine, benzonitrile) with polyether-tailed sulfonate anions. Microelectrode voltammetry in the undiluted melts yields, on the basis of charge transport occurring by electron hopping, electron self-exchange rate constants (k(EX)) for the various Ru3+/2+ couples. The rate constant (and activation barrier) for the pyrazine bridged binuclear pentaamineruthenium melt (Creutz-Taube ion) is similar to those obtained for mononuclear pentaammine[ligand]ruthenium melts, meaning that charge transport in the former is dominated by the rate of intermolecular, not intramolecular, electron transfer. The data at 35 degreesC are (Creutz-Taube ion) k(EX) = 3.7 x 10(4) M-1 s(-1), (pyridine) 1.1 x 10(4) M-1 s(-1), (3-chloropyridine) 2 x 10(4) M-1 s(-1), and (benzonitrile) 3 x 10(4) M-1 s(-1). All k(EX) values are smaller than those for [Ru2+/3+(bpy)(3)] in semisolid melts having equivalent MePEG tail contents.