Excited-state relaxation processes of DPA-DSB: Investigation of the reason for high fluorescence quantum yield of symmetric D-π-D molecule

The temporal evolution of excited states of a symmetric D-π-D structure two-photon absorption material, 1,4-di(4′-N,N-diphenylaminostyryl) benzene (DPA-DSB), was investigated by femtosecond transient absorption spectrum and solvent polarity dependent fluorescence properties. The results suggested that the structure of DPA-DSB did not change much during the intramolecular charge-transfer (ICT) process, which could be the reason for good radiative ability of the ICT state. The major non-radiative deactive channel may be a large structure-changed process, which was formed more slowly than the radiative ICT state. Symmetric charge-transfer in this D-π-D structure molecule could make the non-radiative structure-changed process slow and ineffective, which should be the reason for the high fluorescence quantum yield.