Benzene ring impact on energy transfer system of Eu(TTA)3DPBT

Eu(TTA)3DPBT was found most likely to lead a special singlet photosensitization pathway by means of time-resolved luminescence spectroscopic studies. For further understanding of its intra-molecular energy transfer mechanism, another lanthanide complex Eu(TTA)3BDDT was synthesized, using a related ligand BDDT, changing the D-p-A structure of DPBT to the D-A structure of BDDT. The luminescence characteristics of both complexes were investigated and compared. Results show that p bridge plays an important role in the energy transfer process. p bridge can change the charge separation strength by affecting the electron-density distribution over the diethylaniline and the dipyrazoletriazine moieties. Without the p bridge connection, the benzene ring, BDDT gets a smaller conjugated system, and the absorption peak in the UV-Vis spectrum of BDDT has a blue shift of 114 nm relative to that of DPBT. So the energy level of ligand BDDT and the central ion Eu(III) does not match well, and the energy transfer efficiency drop 33%.