Long-lived photoinduced charge separation in a bridged C60-porphyrin dyad

Long-range photoinduced energy and electron transfer have been investigated in a novel dyad containing a zinc tetraarylporphyrin (PZn) donor and a C60 acceptor separated by a saturated norbornylogous bridge nine sigma bonds in length (PZn-9σ-C60). In non-polar solvents singlet-singlet energy transfer from PZn to C60 is observed but in benzonitrile efficient (> 90%) charge separation occurs with a rate constant of 1 × 1010 sec−1 to yield PZn.+-9σ-C60.−. The charge separated state exhibits a remarkably long lifetime for a dyad of 420 ns. This behaviour is discussed with reference to the energetics, dynamics and orbital symmetry properties of the states involved.