Path-selective photoinduced electron transfer (PET) in a membrane-associated system studied by pH-dependent fluorescence

The pH-dependent fluorescence behavior of two regioisomeric ‘receptor1–spacer1–fluorophore–spacer2–receptor2’ systems 1 and 2 in micellar solutions of sodium dodecyl sulfate show that photoinduced electron transfer (PET) only occurs from the amine group connected to the 4-amino position of the aminonaphthalimide fluorophore in both cases. This demonstrates the directing influence of the photogenerated electric field within the aminonaphthalimide excited state on the electron transfer process. Since path-selectivity of PET is also known within the membrane-bound photosynthetic reaction center in bacteria, its origins may be illuminated by the simple experiments described here.