Femtosecond polarized transient absorption spectroscopy of a C3-symmetric amino-substituted phenylbenzene derivative

The excited-state relaxation processes of an amino-substituted triphenylbenzene derivative (p-EFTP) and its biphenyl-model compound (p-EFBP) were investigated by femtosecond polarized transient absorption spectroscopy. The S 1 –S n absorption was detected upon pumping at 360 nm and probing at 470 nm. Both compounds presented a polarization-dependent component in the transient decay. For p-EFBP a decay time of 97±20 ps was obtained which agrees with the rotational diffusion time determined by time-resolved fluorescence anisotropy. For the symmetric p-EFTP a decay time of 8±2 ps was detected. This value correlates with the intramolecular dipole reorientation time deduced from time-resolved microwave conductivity measurements.