Solvent dependent ultrafast dynamics of multi-branched thiophene-based triphenylamine derivatives with a triazine core

In the present study, we investigated the solvent effect on ultrafast dynamics of the intramolecular charge transfer (ICT) state in multi-branched thiophene-based triphenylamine derivatives with a triazine core (STAPA-a and STAPA-b). The experimental results showed that the fluorescence of STAPA-a and STAPA-b originated from the ICT state. In a weakly polar solvent toluene, the relaxation of the ICT state showed mono-exponential decay due to the absence of the influence of solvent polarity, which directly reflected the fluorescence lifetime. In polar solvents tetrahydrofuran and dichloromethane, accelerated evolutions of ICT states and multi-exponential processes were exhibited because of the interaction between solvent and solute. Furthermore, to explore the influence of the molecular structure on the dynamics of the ICT state, we compared the fluorescence relaxation processes in solvents with different viscosity. We found that the time-resolved properties of STAPA-b exhibit significant differences due to the introduction of alkyl chains.