Ultrafast responses of multi-branched compounds based on 1,3,5-triazine: investigation of the reason for enhanced two-photon absorption property

摘要

The fluorescence and ultrafast response of several modified tri-branched compounds based on 1,3,5-tri-azine (T03-1, T03-2, and T03-3) were investigated to study the effects of stronger electron donor substitution or extended conjugated length on two-photon absorption/two-photon fluorescence and excited-state decay properties. After substitution with a stronger terminal electron donor, N,N-dimethylbenzenamine, the two-photon absorption cross section and fluorescence quantum yield of T03-2 were enhanced by 1.9-fold and 1.4-fold, respectively, compared with T03-1. After extending the conjugated length with thiophene groups connected to π-bridge styryl groups, a similar fluorescence quantum yield and larger two-photon absorption (2.3-fold) of T03-3 were obtained. The ultrafast response processes revealed the effects on the intramolecular charge-transfer properties. These results can also assist in the design of new molecular probes with improved two-photon absorption and two-photon fluorescence properties. Moreover, our study also indicates that these 1,3,5-triazine-based tri-branched derivatives can be employed as molecular probes for biological two-photon fluorescence imaging.