Abstract:The binary complexes of terbium with benzoic acid and its derivatives (phthalic acid, iso-phthalic acid, o-aminobenzoic acid, salicylic acid, sulfosalicylic acid) were synthesized and their compositions were identified by elemental analyses. UV, IR of the complexes were investigated. The UV spectra indicate that the complexes’ ultraviolet absorption is mainly the ligands’   absorption, but the location of peak drifts. The IR spectra show that the IR spectra of complexes are different from those of free ligands, and the band at 400-500cm^-1, due to the stretching vibration of Tb—O, is absent for free ligands. The fluorescence properties were investigated by using luminescence spectroscope, the results show that all the six complexes of terbium exhibit excellent luminescence, due to the transition  from the lowest excited state ⁵D₄ to ⁷F ground state manifold, the complexes of terbium with sulfosalicylic acid have the strongest fluorescence intensity, and is stronger than o-aminobenzoic acid-terbium, whose fluorescence intensity is regarded as the strongest one in the literature, and even stronger than some phosphor of terbium.

Key words: rare earth; terbium; benzoic acid; fluorescence; complexes