Distance dependence of singlet and triplet charge recombination pathways in a series of rigid bichromophoric systems

The recombination process of the charge-separated state in a series of rigid donor-bridge-acceptor compounds 1[n] follows two pathways, viz, recombination to the singlet ground state and recombination to the local triplet donor state. The rates of both these processes are shown to depend exponentially on distance, but with a significantly different damping factor. Thus at short distances singlet recombination is dominant, while at longer distances the triplet pathway eventually becomes the major process.