2-(2-Hydroxyphenyl) substituted benzimidazole derivatives: Suitable sensitizers for Tb³⁺ characteristic luminescence

Two series of 2-(2-hydroxyphenyl) substituted benzimidazole derivatives, (1-phenyl-2-(2-hydroxy-3-methoxyphenyl)benzimidazole, HL1; 1-methyl-2-(2-hydroxy-3-methoxyphenyl)benzimidazole, HL2) and their bimetallic complexes Zn-Ln(III)-L (Ln = Tb, Nd, Eu and Y) were prepared. The structures of ligands and complexes were characterized by H-1-NMR, FT-IR and single crystal X-ray diffraction. The UV-Visible absorption spectra, emission spectra and luminescent lifetime were measured. These results suggested that the ligands could efficiently sensitize the characteristic luminescence of Tb(III) and the photoluminescence quantum yield(PLQY) for Tb(III) complexes 3 and 7 were 74.8% and 55.3% respectively. While Nd(III) complexes 1 and 5 shown weak emission, and the Eu(III) complexes could not give the typical emission of lanthanide ions maybe due to the photo-induced electron transfer. In addition, the internal quantum yields of Nd(III) complexes were calculated utilizing luminescent lifetime.