Synthesis, Crystal Structure and Characterization of Two Terbium Complexes with Bromobenzoic Acid

Two complexes of [Tb(2-BrBA)2(CH3COO)(2, 2'-bipy)]2 (1) and [Tb(3-BrBA)3(2, 2'-bipy)]2(3-HBrBA)•2H2O (2) (2-BrBA=2-bromobenzoate, 3-BrBA=3-bromobenzoate, 2, 2'-bipy=2, 2'-bipyridine) were synthesized by solvent method and their structures were determined by X-ray single crystal diffraction method. Complexes 1 and 2 both belong to triclinic system and P(average)1 space group. The complex 1 is a dimer with an inversion center, in which two different carboxylate ligands coordinate to Tb(superscript 3+) ion simultaneously to form quaternary mixed-ligands complex. Four 2-BrBA ligands link the two Tb(superscript 3+) ions by bidentate-bridging mode, two acetate ligands coordinate to two Tb(superscript 3+) ions by bidentate-chelating mode, and two 2, 2'-bipy molecules chelate to two Tb(superscript 3+) ion, respectively. The ternary complex 2 is also a dimer with an inversion center, in which the two Tb(superscript 3+) ions are linked by four bidentate-bridging 3-BrBA ligands and each Tb(superscript 3+) ion is further bonded to one bidentate-chelating 3-BrBA ligand and one 2, 2'-bipy molecule. The two complexes exhibit strong green fluorescence under ultraviolet light and the fluorescence spectrums of them both have four peaks at 489, 545, 585 and 621 nm corresponding to 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3 transition emissions of the Tb(superscript 3+) ion, respectively.