Photoinduced electron transfer in azatriangulenium salts

Fluorescence quenching and laser flash photolysis studies of stable azatriangulenium ions 2⊕–4⊕ are reported. The fluorescence quenching rate constants were correlated to ΔG0 values. The results suggest that 2⊕ is an excited state electron acceptor and 4⊕ is an excited state electron donor. 3⊕, on the other hand, can act as an acceptor or donor in photoinduced electron transfer (PET) reactions. Laser flash photolysis studies also supported these observations. These cations thus present an interesting case, where replacement of oxygen atoms by N-alkyl groups leads to a gradual shift of photoinduced electron transfer property from an acceptor to that of a donor.