PHOTOINDUCED INTRAMOLECULAR ELECTRON-TRANSFER IN P-POLYPHENYLAMINES AND 1-(P(N,N-DIALKYLAMINO)-P-POLYPHENYL)NAPHTHALENES

Photoinduced intramolecular electron transfer in two series of aromatic amines of the type aryl-(C6H4),-NR(2), where aryl is phenyl and l-naphthyl and n = 1-3, has been studied. From the solvatochromic behavior of the fluorescences from these compounds, excited-state dipole moments ranging from 10.9 to 29.9 D have been measured, suggesting that the emissions occur from charge-transfer states, except in 4-(N,N-diethylamino)biphenyl (aryl = phenyl; n = 1). The large quantum yields and short fluorescence lifetimes indicate efficient electronic communication between the donor and acceptor (k(et) > 10(8) s(-1)). Good agreement was found between the observed and calculated fluorescence energies in polar solvents using a simple electrostatic model. The results suggest that the phenyl rings in the extended systems act as part of the donor or acceptor moieties in electron transfer and are not spacer (or insulating) groups.