The covalent attachment of poly(ethylene oxide) chains to metal bipyridine complexes produces viscous molecular melts with sufficient ionic conductivity to permit microelectrode voltammetry. This paper describes the use of this chemistry to prepare a new copper complex with "tailed" bipyridine ligands, [Cu(bpy(CO(2)MePEG-350)(2))(2)](ClO4)(2), where MePEG-350 is methyl poly(ethylene glycol) with molecular weight 350 g mol(-1). The coupling of physical diffusion with electron hopping during voltammetry allows measurement of the electron self-exchange rate constant, k(EX), for the Cu(II/I) couple. Activation studies indicate the reaction to be nearly adiabatic, with an activation barrier larger than expected for purely inner-sphere rearrangements. This study also examines the depression of both electron transport and ionic conductivity caused by the addition of 1.4 M LiClO4 to the undiluted room-temperature melt.