TEMPERATURE DEPENDENCE OF PHOTOSENSITIZED ELECTRON TRANSPORT ACROSS LIPID VESICLE WALLS

Abstract— An overall Arrhenius activation energy of 117 plusmn; 19 kJ/mol (28.0 plusmn; 4.5 kcal/mol) has been measured for photosensitized electron transport across phospholipid vesicle walls in the temperature range 18–38°C. A dynamic model for the overall process is proposed which accounts for the parabolic growth curves of the kinetically probed species, heptyl viologen radical. The temperature dependence of the initial quantum yield derived from these curves, and of fluorescence quenching behavior of the ruthenium tris-bipyridyl photosensitizer, is used to estimate an activation energy of 67 plusmn; 21 kJ/mol(16 plusmn; 5 kcal/mol) for the electron transport step itself. The activation energy for the co-transport of charge compensating ions is estimated to contribute no more than 4.6 kJ/mol to this energy.