Intramolecular multiple Rehm-Weller plots in photoinduced electron transfer: competition between pi- and n-type donor sites in benzylamines

Earlier PET work has suggested that, for a given electron acceptor, distinc t pi- and n-type electron donors lead to distinct Rehm-Weller plots due to different Coulomb terms (C-terms) C-pi and C-n, respectively. We studied be nzylamine donors which embody both types of donor site. The results support the key role of the C-term in determining electron transfer efficiencies. A thorough evaluation of the adiabatic ionization potential (IP,) of the pi - and the n-moiety, serving as a measure of the corresponding relative oxid ation potential (E-ox), was crucial to arrive at these findings. Hence, for an electron donor embodying more than one donor site the observable PET ra te constant is not necessarily related to the easiest oxidizable site, i.e. to E-ox. This does not apply to photoinduced charge shift as here the C-te rm does not contribute to the driving force. Earlier useful correlations be tween E-ox and IPa for pi- and n-donors were updated.