Synthesis, crystal structures and fluorescence properties of dinuclear Tb(III) and Sm(III) complexes with 2,4,6-tri(2-pyridyl)-1,3,5-triazine and halogenated benzoic acid

Three ternary lanthanide complexes with o-bromobenzoic (o-BrBA), o-chlorobenzoic acid (o-ClBA) and 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) have been synthesized. These complexes were characterized by elementary analysis, UV absorption spectroscopy and IR spectroscopy. The crystal structures of [Tb2(TPTZ)2(o-BrBA)4(NO3)2(H2O)2] (1), [Tb2(TPTZ)2(o-ClBA)3(NO3)2(H2O)3]·o-ClBA·C2H5OH·2H2O (2) and [Sm2(TPTZ)2(o-ClBA)4(NO3)2(H2O)2] (3) were determined by single-crystal X-ray diffraction, and they were all dinuclear complexes with the characteristic of triclinic and P - 1 space group. The crystals 1 and 3 were isostructural, whose center ions were bridged by μ2-o-BrBA−/μ2-o-ClBA− ions and the coordinate number of the central metal ions were nine, composed by a η3-TPTZ, two bridging bidentates and one monodentate o-BrBA (o-ClBA) ligand, a bidentate NO3− and a coordinated water molecule. But the structure of complex 2 was asymmetric and the two Tb(III) ions have different coordination surroundings. Furthermore, the luminescence spectra and luminescence lifetimes of three crystals were then measured. Besides, the two Tb(III) complexes exhibit high emission quantum efficiencies.