The sorption of CO2 into the highly viscous, semisolid hybrid redox polyether melt, [Co(phenanthroline)3](MePEG-SO3)2, where MePEG-SO3 is a MW 350 polyether-tailed sulfonate anion, remarkably accelerates charge transport in this molten salt material. Electrochemical measurements show that as CO2 pressure is increased from 0 to 800 psi (54 atm) at 23 °C, the physical diffusion coefficient DPHYS of the Co(II) species, the rate constant kEX for Co(II/I) electron self-exchange, and the physical diffusion coefficient of the counterion DCOUNTERION all increase, from 4.3 × 10-10 to 6.4 × 10-9 cm2/s, 4.1 × 106 to 1.6 × 107 M-1 s-1, and 3.3 × 10-9 to 1.6 x 10-8 cm2/s, respectively. Plots of log(kEX) versus log(DPHYS) and of log(kEX) versus log(DCOUNTERION) are linear, showing that electron self-exchange rate constants are closely associated with processes that also govern DPHYS and DCOUNTERION. Slopes of the plots are 0.68 and 0.98, respectively, indicating a better linear correlation between kEX and DCOUNTERION. The evidence indi0cates that kEX can be controlled by relaxation of the counterion atmosphere about the Co complexes in the semisolid redox polyether melts. Because the counterion relaxation is in turn controlled by polyether "solvent" fluctuations, this is a new form of solvent dynamics control of electron transfer.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry