Amino derivatives of symmetric 1,3,5-triphenylbenzene. Nature of the polar singlet excited state.

Abstract The solvent dependence of the fluorescence spectra of (dialkylamino) and (diarylamino) substituted triphenylbenzene derivatives indicates that the emission occurs from a highly polar excited state. The exponential fluorescence decays, obtained with time correlated single photon timing, suggest that equilibration between the different excited species occurs within the time resolution of the experimental set-up. For 5′-(3-(diethylamino)phenyl)-N,N,N′,N′-tetrakisethyl-(1,1′:3′,1″-terphenyl)-3,3″-diamine the size of the excited state dipole moment excludes the formation of a TICT state. For (4(bis(4-ethylphenyl)amino)phenyl)-N,N,N′,N′-tetrakis(4-ethylphenyl)(1,1′:3′,1″-terphenyl)-4,4″-diamine the large fluorescent rate constant in polar solvents suggests the formation of a conjugated intramolecular charge transfer state. Only for (4-(diethylamino)phenyl)-N,N,N′,N′-tetrakis-ethyl-(1,1′:3′,1″-terphenyl)-4,4″-diamine the experimental evidence does not allow to exclude either the formation of a TICT state or a delocalized ICT state.