INTRAMOLECULAR PHOTOASSOCIATION AND PHOTOINDUCED CHARGE-TRANSFER IN BRIDGED DIARYL COMPOUNDS .2. CHARGE-TRANSFER INTERACTIONS IN THE LOWEST EXCITED SINGLET-STATE OF DINAPHTHYLAMINES

The formation of an intramolecular charge-transfer (CT) exciplex is demonstrated for 1,1'-dinaphthylamine (1,1'-DNA) and 2,2'-dinaphthylamine (2,2'-DNA) in the lowest excited singlet state using steady-state and picosecond time-resolved fluorescence spectroscopy. The exciplex is formed through a mutual reorientation of the two naphthalene rings. Differences in the rate of formation and relaxation of the CT state for 1,1'-DNA and 2,2'-DNA indicate the importance of the bridge position in this process. The comparison of the steady-state fluorescence of 2,2'-DNA with that of its protonated form, as well as the fluorescence of 2,2'-dinaphthyl ether and 2,2'-dinaphthylmethane, show the role of the lone-pair electrons of the nitrogen atom in the exciplex formation.