4-卤代苯甲酸铽配合物荧光性能的研究

Fluorescent Properties of Rare Earth Complexes Formed by Terbium Ion and Halogenated Benzoic Acids

以4-氯苯甲酸(4-ClBA)、4-溴苯甲酸(4-BrBA)和4-碘苯甲酸(4-IBA)为配体合成了三种4-卤代苯甲酸铽的稀土配合物Tb(4-ClBA)3,Tb(4-BrBA)3和Tb(4-IBA)3,紫外可见光吸收光谱表明,相同摩尔浓度的Tb(4-IBA)3的紫外吸收最强,Tb(4-BrBA)3的紫外吸收强度次之,Tb(4-ClBA)3的紫外吸收最弱,而荧光发射光谱表明,Tb(4-IBA)3和Tb(4-BrBA)3的荧光发射强度远小于Tb(4-ClBA)3的。从配体的结构及配体能级、稀土离子Tb3+能级、配体到稀土离子之间的能量传递等角度对该试验结果进行了分析探讨,结果表明苯甲酸对位的碘原子、溴原子和氯原子与苯环上的碳原子所形成的碳卤键热振动的不同是造成三种稀土配合物荧光强度差别较大的本质原因。

The rare earth complexes Tb（4-ClBA）3,Tb（4-BrBA）3 and Tb（4-IBA）3 were synthesized using chloro benzoic acid,bromide benzoic acid and iodo-benzoic acid as ligands,respectively.The UV-visible spectra showed that absorption of Tb（4-IBA）3 was much stronger than those of Tb（4-ClBA）3 and Tb（4-BrBA）3 with same molar concentration,and the absorption of Tb（4-ClBA）3 was the weakest.However,the fluorescent intensity of Tb（4-ClBA）3 was much stronger than those of Tb（4-BrBA）3 and Tb（4-IBA）3,and the fluorescent intensity of Tb（4-IBA）3 was the weakest.In this paper,the structure and the energy level of ligands,the energy level of Tb3＋ and energy transfer process from ligands to Tb3＋ were discussed to explain the experimental results.The thermal vibration of carbon-halogen bond formed by halogen atoms and carbon in the benzene ring was the essential reason for larger difference of fluorescent intensities of the three kinds of rare earth complexes.