Photoinduced electron transfer dynamics in porphyrin donor dyads

Abstract

Intramolecular photoinduced electron transfer (PET) processes occurring in dyads with a free base porphyrin-tetraazaanthracene donor (P) and either a tetracyanonaphthoquinidodimethane (TCQ) or benzoquinone (BQ) acceptor linked by a rigid six σ-bond polynorbornane bridge ([6]) have been investigated. For P[6]BQ, PET in the polar solvent benzonitrile (εs = 25.9) occurs with a rate constant (kPET) of 1.6 × 108 s-1 but is not evident in solvents less polar than tetrahydrofuran (εs = 7.52). For P[6]TCQ, highly efficient forward PET occurs in both polar and non-polar solvents (kPET > 2 × 1010 s-1). For P[6]TCQ the lifetime of the resulting charge-separated state decreases markedly with increasing ..