Tao Dong-Liang, Zhang Kun, Zhang Hong, Cui Yu-Min, Xu Yi-Zhuang, Liu Yu-Hai
Guang Pu Xue Yu Guang Pu Fen Xi. 2014 Apr;34(4):994-8.
Tb(2-FBA)3 x 2H2O and Tb(2-FBA)3 phen were synthesized using o-fluoro-benzoic acid (2-FBA) as the first ligand, and 1,10-phenanthroline (phen) as the second ligand. Elemental analysis and IR spectra were employed to characterize the molecular composition of the two kinds of lanthanide complexes. The UV absorption spectra with same concentration show that the second ligand phen of Tb(2-FBA)3 phen absorbs the portion of the UV light instead of the first ligand 2-FBA. Liquid fluorescence spectra with same concentration show that the fluorescence intensity of Tb(2-FBA)3 x 2H2O is higher than that of Tb (2-FBA)3 phen. The analytical results show that the energy level of 2-FBA matches the lowest excited state energy level of Tb3+ (5D4) better than that of phen. The O-H oscillation of the crystal water in Tb(2-FBA)3 x 2H2O will greatly consume the absorbed energy by ligands, and cause the fluorescence intensity of Tb(2-FBA)3 x 2H2O significantly decline. The energy level of triplet state of the first ligand 2-FBA corresponding to the absorption peak 273 nm has poor matching degree with the 5D4 energy level of Tb3+. In this case, the emission intensity of Tb(2-FBA)3 x 2H2O is still stronger than that of Tb(2-FBA)3 phen. It illustrates that the energy level of the triplet state of the first ligand 2-FBA corresponding to 252 nm has much better matching degree with the lowest excited state of 5D4 energy level of Tb3+ than that of phen. It is the only way to compensate for energy loss by thermal vibration of water molecules and low energy transfer efficiency for poor matching degree between the energy level of corresponding to 273 nm of the first ligand 2-FBA and 5D4 energy level of Tb3+. By combining UV absorption spectra with fluorescence spectra of lanthanide complexes to qualitatively analyze energy level of ligands, the contribution of different types of ligands to the fluorescence properties can be preliminarily understood.
以邻氟苯甲酸（2 - FBA）作为第一配体，1,10 - 菲咯啉（phen）作为第二配体，合成了Tb(2 - FBA)₃·2H₂O和Tb(2 - FBA)₃phen。采用元素分析和红外光谱对这两种镧系配合物的分子组成进行表征。相同浓度下的紫外吸收光谱表明，Tb(2 - FBA)₃phen中的第二配体phen吸收了紫外光的一部分，而不是第一配体2 - FBA。相同浓度下的液体荧光光谱表明，Tb(2 - FBA)₃·2H₂O的荧光强度高于Tb(2 - FBA)₃phen。分析结果表明，2 - FBA的能级比phen与Tb³⁺（⁵D₄）的最低激发态能级匹配得更好。Tb(2 - FBA)₃·2H₂O中结晶水的O - H振动会大量消耗配体吸收的能量，导致Tb(2 - FBA)₃·2H₂O的荧光强度显著下降。对应于273 nm吸收峰的第一配体2 - FBA的三重态能级与Tb³⁺的⁵D₄能级匹配度较差。在这种情况下，Tb(2 - FBA)₃·2H₂O的发射强度仍强于Tb(2 - FBA)₃phen。这说明对应于252 nm的第一配体2 - FBA的三重态能级与Tb³⁺的⁵D₄最低激发态的匹配度比phen好得多。这是弥补水分子热振动能量损失以及第一配体2 - FBA对应于273 nm的能级与Tb³⁺的⁵D₄能级匹配度差导致的低能量转移效率的唯一途径。通过将镧系配合物的紫外吸收光谱与荧光光谱相结合来定性分析配体的能级，可以初步了解不同类型配体对荧光性质的贡献。
