Electron transfer rate constants of several derivatives of [5-(4'-(4"-(2"',5"'-benzoquinonyl)bicyclo[2.2.2]octyl) )-2,3,7,8,12,13,17,18-octamethylporphyrinato]zinc(II) have been measured as a function of temperature 2-methyltetrahydrofuran, toluene, and toluene-d_g. The observed temperature dependencies of the electron transfer constants are relatively weak in both the polar and nonpolar solvents. Nonexponential ET dynamics are observed low temperatures and described in terms of an initial (k_(ET)^0) and an average ET rate constant (k_(av)). The k_(ET)^0 values the molecules with different driving forces, spanning a range of 0.2 eV, show parallel trends over the range of studied. The trends in k_(ET)^0 are described in terms of the effects of temperature-dependent changes in dielectric constants on the barrier height. Good agreement is observed for the case of toluene solvent, using semiclassical model, but poorer quantitative agreement is found for the 2-methyltetrahydrofuran data. The temperature of k_(av) is described using a model incorporating an angle-dependent electronic coupling and interconversion rotational conformers. A temperature-dependent solvent isotope effect is observed on going from toluene to toluene-d_8, k_(ET)^0( toluene)/k_(ET)^0( toluene-d_8) being as large at 1.5 over the range of temperatures studied.
No takes yet. Share an insight, caveat, or question.
Khundkar et al. (1994) studied this question.