Combining redox active moieties with polyether oligomers produces amorphous, highly viscous, room-temperature molten materials notable for their high concentrations of redox sites that in mixed valent form exhibit facile electron-transfer chemistry. This paper describes experimental determinations and comparison of thermal and optical energy barriers for electron transfers in a specific redox polyether melt, namely the metal complex Ru(bpy350)(2)(CN)(2) where bpy350 is 4,4'-dimethyl-2,2'-dipyridyl alkyl-bonded to 350 MW polyethylene glycol monomethyl ether. Electrochemical measurements provide apparent electron self-exchange rate constants (k(EX)) within the Ru(III/II) form of the melt and physical diffusion rates of perchlorate ion (D-Cl04), along with the associated thermal activation barrier energies. Plasticization by CO2 induced swelling of the melt results in enhanced mass and charge transport rates and decreasing energy barriers for both. Optical spectra of the same, electrochemically generated, mixed valent melt display an absorbance interpreted as an intermolecular Ru(II-->III) intervalence charge transfer band. The energy barrier results show that the observed thermal electron transfer energy barrier is only an apparent one, being instead controlled by ion atmosphere relaxation processes, whereas the optical energy barrier corresponds to that of the actual electron-transfer process itself.