Transport, ionic conductivity, and viscosity properties of the metal complex molten salt [Co(bpy(CO2MePEG-350)2)3](ClO4) 2 (MePEG = monomethyl-terminated polyether, average MW = 350) are strongly affected by dissolution of LiClO4 electrolyte in the melt. The physical self-diffusion of the [Co(bpy(CO2MePEG-350)2)3]2+ and the rate of [Co(bpy(CO2MePEG-350)2)3]2+/+ electron self-exchange are slowed, the melt viscosity increased and ionic conductivity decreased, and thermal activation barriers for all are enhanced by increasing [LiClO4]. Most of the effects are associated with the Li+ cation/polyether coordination well-known in polymer electrolytes, in which chain cross-linking and a decrease in chain segmental mobility occurs. The [Co(bpy(CO2MePEG-350)2)3]2+/+ electron self-exchange reaction is shown to be adiabatic (kinetic prefactor ca. 1013 s-1), and modest changes in its rate with [LiClO4] are caused by changes in the electron transfer barrier energy. The results are used to draw a hierarchy of dynamics in the metal complex melt in which, for [LiClO4] = 1.3 M, the average diffusive jump rate is ca. 3 s-1, the average electron hopping rate is ca. 3 s-1, and the rate of short-range motions of the hard metal complex core within its soft polyether shell (producing adjacent core - core contacts) is ca. ≥ 105 s-1.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry