ELECTRON-TRANSFER AND MAGNETIC-FIELD EFFECTS IN DONOR-ACCEPTOR SYSTEMS LINKED BY A HYDROCARBON CHAIN INCORPORATING PHENYL GROUPS

Fluorescence quenching experiments and studies of the spin dynamics in intramolecular radical ion pairs are presented. Compounds investigate d are bichromophoric molecules containing 1-pyrenyl (Py) and 4-N,N-dim ethylaminophenyl (DMA), linked by a hydrocarbon chain incorporating ph enyl groups (Phi). The results demonstrate the participation of the ar omatic spacers in the primary electron transfer process. Such a spacer -molecule-assisted mechanism, however, seems to be absent in the recom bination reaction (return electron transfer) of the radical ion pair. Hyperfine-driven spin mixing, leading to a magnetic field effect in th e triplet and exciplex yields, has only been observed with the compoun d with a longer chain, namely Py-CH2-Phi-(CH2)(2)-Phi-CH2-DMA in aceto nitrile.