稀土(铕-铽)-18冠6-对苯二甲酸配合物的荧光性能

Fluorescence Property of the Complexes of the RE(Eu-Tb)-18C6- p-Phthalic Acid

以对苯二甲酸(L′)为桥联配体,18冠6(L)为配体,稀土(Eu Tb)为中心离子,合成了一系列超分子化合物,对其进行了元素分析,红外光谱及荧光性能测量。确定了配合物的组成为(Eu1-xTbx)2L2L′(ClO4)4·H2O(6+3x);推测出Eu3+离子直接与冠醚氧原子配位,而较小半径的Tb3+与18冠6则通过H2O配位。H2O分子与冠醚氧原子以氢键形式连结,对苯二甲酸以双齿形式桥联两个稀土离子冠醚配合物,形成双核结构单元;在此配合物中,Tb3+离子对Eu3+离子的发光有一定的敏化作用,而Eu3+离子对Tb3+离子的荧光却有强的猝灭作用。

A series of dinuclear complexes with different Eu^(3+) to Tb^(3+) ratios with p-phthalic acid (L′) and ligand of 18 crown 6 (L) have been synthesized. Elemental analysis,IR absorption spectra and fluorescence spectra have been studied respectively.The compositions of the complexes were confirmed to be(Eu_(1-x)Tb_x)_2L_2L′(ClO_4)_4·H_2O_((6+3x)). Smaller Tb^(3+) coordinated with water molecules, which were hydrogen bonded with crown ether while Eu^(3+) coordinated with crown ether directly may be concluded.Shimadzu FR-5301PC fluorescence spectrophotometer was employed to measure the luminescence spectra at room temperature. As results showed the excitation wavelength changed with the molar ratios of Eu^(3+) to Tb^(3+). The optimum excited wavelength is at the same position(298 nm) when contents of Tb^(3+) is 100% and 90%, respectively. It changes to 254 nm when Tb^(3+) content decrease to 70% and Eu^(3+) content rise to 30%. The measurement results of the emission spectra of the complexes indicated that the emission peaks of Tb_2L_2L′(ClO_4)_4·12H_2O consisted of four groups of emission peaks and Eu_2L_2L′(ClO_4)_4·6H_2O has three, while (Eu_(1-x)Tb_x)_2L_2L′(ClO_4)_4·H_2O_((6+3x)) has five. The previous are as following: peaks at 490.0, 545.8, 585.6 and 621.0 nm are as the Tb^(3+) ions^5D_4→~7F_J(J=6,5,4,3) transitions correspondingly, among them the emission from^5D_4→~7F_5 is the strongest belonging to hypersensitive transition(ΔJ=2). The latter are following: first group, 578.6 nm belongs to^5D_0→~7F_0 transitions of Eu^(3+), the second group,588.2 nm and 592.2 nm, both belong to^5D_0→~7F_1 transitions of Eu^(3+), the third group, 613.6nm and 618.2 nm both belong to^5D_0→~7F_2 transitions of Eu^(3+). The last one: they appear at about 490, 545, 579, 585 and 620 nm. The first and second fluorescence bands centered around 490 nm and 545 nm corresponding to^5D_4→_7F_6 and^5D_4→~7F_5 transitions of Tb^(3+) ions. Overlapped peaks at 585 nm and 620 nm were found caused by interaction between^5D_0→~7F_1 ,~5D_0→~7F_2 transitions of Eu^(3+)and^5D_0→~7F_4 ,~5D_4→~7F_3 transitions of Tb^(3+). Variance of fluorescence spectra emission peaks showed that there are interaction between Eu^(3+) ions and Tb^(3+) ions in (Eu_(1-x)Tb_x)_2L_2L′(ClO_4)_4·H_2O_((6+3x)).The fluorescence emission intensity of Tb^(3+) (~5D_4→~7F_5) in Tb_2L_2L′(ClO_4)_4·12H_2O was 1 313.6 comparing with 29.8 of Eu^(3+) (~5D_0→~7F_2) transitions in Eu_2L_2L′(ClO_4)_4·6H_2O. Concluded from R=I_d/I_c(I_d=values of the fluorescence emission intensity determined, I_c=calculated values) is below 1.0 at 490 nm and 545 nm (corresponding to Tb^(3+)~5D_4→~7F_6 and^5D_4→~7F_5 transitions) even at 585 nm. However when ratio of Eu^(3+) and Tb^(3+) is 0.9∶0.1～0.7∶0.3, the R values for peaks at 579 nm and 620 nm are higher than 1.0 collectively, Eu^(3+) will quench Tb^(3+) fluorescence while Tb^(3+) will sensitize Eu^(3+).