双酰胺配体铕和铽混合固态配合物的光谱研究

在氯仿和乙酸乙酯溶液中合成了以1,6-二(2’-苄胺甲酰基)苯甲氧基]己烷(L)为配体的硝酸铕和硝酸铽配合物，以及不同摩尔比的铕和铽的共沉淀配合物，又按不同的摩尔比将单一的硝酸铕和硝酸铽配合物通过研磨混合，得到混合固态的铕铽配合物。通过元素分析、红外光谱、紫外光谱、XPS 光电子能谱对配合物进行了表征，结果表明：单一稀土硝酸盐与配体形成的是2∶3型的配合物；所有的配合物都具有相似的配位结构；与单一稀土配合物相比，相同摩尔比的混合配合物的紫外吸收有所降低；混合配合物中发生了一定的化学键合作用，电子结合能有变化。通过荧光光谱对这些配合物的荧光性质进行了详细的研究, 表明与单一的铕和铽配合物相比，两种混合固态配合物无论是荧光发射峰位还是荧光强度均发生了明显变化，铽对铕的荧光强度有很强的敏化作用，铕对铽的荧光强度有猝灭作用。在紫外灯的照射下，共沉淀配合物的荧光颜色随着摩尔比的变化呈现有规律的变化。

Study on Spectroscopic Properties of Eu and Tb Mixed Solid Complexes with a Diamide Ligand

In the present work, Eu(NO₃)₃ and Tb(NO₃)₃ complexes with a diamide ligand 1,6-bis(2’-benzylaminoformyl)phenoxyl]hexane (L) were prepared in the solution of chloroform and ethyl acetate.Their mixed complexes with different molar ratio also synthesized by coprecipitation.Eu and Tb complexes were mixed with different molar ratio, mechanically ground, and a series of mixed solid complexes were obtained.These mixed complexes were characterized by elemental analysis, UV-Vis, IR and XPS spectra.The analytical data were obtained by a Vario EL CHN and indicated that Eu and Tb complexes formed a 2∶3 metal-to-ligand stoichiometries 2RE(NO₃)₃·3L·4H₂O.Their IR spectra were recorded on a Bruke FTS66V/S spectrophotometer.The results indicate that all complexes have similar IR spectra, of which the characteristic bands have similar shifts, suggesting that they have a similar coordination structure.UV-Vis spectra were recorded on a Hitachi U-3010 spectrophotometer and showed that under the influence of the mixed ions, the absorbance of the mixed complexes is not identical with that of the pure complexes.XPS spectra were analyzed on a PHI-5702 X-ray photoelectron spectroscope (XPS) operating with monochromatic Mg Kα irradiation at pass energy of 29.4 eV.The binding energies of O(1s), Eu(3d) and Tb(4d) in the two kinds of mixed complexes were changed compared with Eu-L and Tb-L complexes.This indicates that these two synthetic methods were not a simple physical mixing process, but there was some chemical effect between the mixed Eu-L and Tb-L complexes.The fluorescence spectra of the mixed complexes were obtained on a Hitachi F-4500 spectrophotometer at room temperature.The excitation and emission slit widths was 1.0 nm.It was concluded from the excitation spectra that the best excitation wavelengths for Eu and Tb complexes are 396 and 320 nm respectively.For the convenience of comparing the fluorescence intensities with each other, the excitation wavelengths were set to 320 nm.For the mixed complexes prepared by coprecipitation, the peak positions of the 5D₄→7F₆ and 5D₄→7F₅ transitions were not changed.The peak at 590 nm was assigned to the 5D₀→7F₁ and 5D₄→7F₄ transitions.Its position is dependent on the content of Eu and Tb complexes.When the content of Eu complex is large, this peak is near to the position of the 5D₀→7F₁ transition, but when the content of Tb complex is large, it is near to the position of the 5D₄→7F₄ transition.The peak at 620 nm is a combined peak of the 5D₀→7F₂ and 5D₄→7F₃ transitions.It has a similar change with the peak at 590 nm.The change of these peak positions could indicate that there was interaction between Eu and Tb complexes.The fluorescence intensities of the mixed solid complexes were changed obviously as compared with the pure Eu and Tb complexes.The fluorescence intensities of their 5D4→7F₆ and 5D₄→7F₅ transitions were lower than those of the Tb complex as well as the theoretical values calculated by the molar ratio of Tb complex, and decreased with the increase in the content of Eu complex, which shows that the fluorescence intensities of terbium ions were quenched by europium ions.The fluorescence intensities of the two combined peaks at 590 and 620 nm are higher than that of Eu complex but lower than that Tb complex and they increased with the increase in the content of Tb complex, which indicates that the fluorescence intensities of Eu3+ were sensitized by Tb3+.In the mixed complexes prepared by grinding, the fluorescence intensities of Eu3+ were also sensitized by Tb3+ and the fluorescence intensities of Tb3+ are also quenched by Eu3+.Under the excitation of UV light, the mixed complexes resulted by coprecipitation exhibit different fluorescence color.