Synthesis, characterization, luminescence properties and deciphering the role of a terpyridyl-imidazole based ligand in the dissimilar luminescence sensitization of ternary lanthanide(iii) tris-(β-diketonate) complexes

Abstract

We designed four ternary lanthanide tris-(β-diketonate) complexes of the form [Ln(tta)₃(tpy-HImzphen)], where Ln = La^III, Eu^III, Sm^III and Tb^III; tta = (2-theonyltrifluoroacetonate) and tpy-HImzphen = 2-(4-[2,2′:6′,2′′]terpyridin-4′-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. All the complexes have been thoroughly characterized by standard analytical tools and spectroscopic techniques including single crystal X-ray diffraction. In situ generation of the complexes was also monitored via absorption and emission spectroscopy upon incremental addition of the respective lanthanide precursor {Ln(tta)₃(H₂O)₂} to the dichloromethane solution of the terpyridyl-imidazole ligand. The photophysical behaviors of all the complexes were thoroughly investigated via absorption and both steady-state and time-resolved emission spectroscopic techniques. The emission spectral measurements were carried out at both room temperature and 77 K to understand the deactivation dynamics of the excited states and elucidate the distinctive luminescence responses from the four lanthanide metal ions owing to the introduction of the terpyridyl-based ancillary ligand.