Spin control of the lifetime of an intramolecular charge-transfer excited state

Triplet-sensitized generation of a long-lived intramolecular charge-separated excited state is described in an electron donor - acceptor molecule with a short distance between the donor and the acceptor. Time-resolved UV-Vis optical absorption spectroscopy shows that the lifetime of this triplet excited state is 1.4 mus in acetonitrile at 298 K, i.e. five orders of magnitude greater than that of the corresponding singlet charge-separated state. In slightly less polar alkane nitrile solvents, the local and CT triplet states coexist, which allows determination of their relative energies.