Effect of central metal on intra-molecular exciplex of porphyrin–fullerene double linked dyad

The photoinduced electron transfer reaction of porphyrin–fullerene dyads occurs through an intermediate state, previously identified as a preformed intramolecular exciplex, emitting in the near infrared region (NIR). It can also be seen as a weak absorption band in NIR commonly called the charge transfer absorption band. A detailed analysis of the absorption and emission features of a series of double-linked dyads reported in this Letter leads to the conclusion that the state is characterized by a shift of 40% of the electron density from the porphyrin donor to the fullerene acceptor.