Intramolecular benzene excimer formation in 13,14-diphenyldibenzo[b,j][4,7]phenanthroline.

13,14-diphenyldibenzo[b,j][4,7]phenanthroline (DBP3) in various solvents was studied by time-resolved fluorescence and fs transient absorption (fs-TA) spectroscopy. An intramolecular benzene excimer is demonstrated to form within DBP3; it exhibits strong redshifted emission with maximum at 540-640 nm. "Intrinsic" fluorescence from DBP3 is dramatically quenched down to τ = 50-400 fs in all the solvents studied. Fs-TA and time-resolved fluorescence spectra have proved that relaxed intramolecular benzene excimer is formed from S1 state via hot excimer state with three lifetime components: 50 fs, ∼3.5 ps, and ∼25 ps, which are of the inertial (electronic) and diffusive parts of the relaxation due to solute-solvent interaction. Formation of triplet states via intersystem crossing was observed directly from the upper excited electronic states of DBP3.