铀(Ⅵ)和三辛基氧化膦配合物在离子液体中的电化学与光谱性质

选择具有代表性的中性含磷萃取剂三辛基氧化膦（TOPO）作为配体，考察其与高氯酸铀酰在疏水离子液体［N₄₁₁₁］［NTf₂］中形成配合物的光谱和电化学行为。该配合物在离子液体中的紫外 可见吸收光谱呈现出峰间距为(728±9)cm^-1的电子振动带系，其红外光谱中铀酰离子不对称伸缩振动频率（ν_as）为926cm^-1。电化学研究显示，［UO₂(TOPO)₄］²⁺的电极还原过程由两个连续的单电子还原过程组成，对应的还原峰电位分别为E_pc1=-1.37V和E_pc2=-1.75V（vs. Ag⁺/Ag），其中前者为准可逆，后者不可逆。该U(Ⅵ)→U(Ⅴ)准可逆过程的半波电位E_1/2=-1.33V，不随扫描速率和温度改变，说明该过程可逆性较好，且还原产物稳定。该配合物的扩散活化能为E_a=(39.0±1.1)kJ/mol。该体系可能在以离子液体为介质的电化学分离过程中具有潜在的应用前景。

Electrochemical and Spectroscopic Characteristics of Uranyl-Trioctylphosphine Oxide(TOPO) Complex in Ionic Liquid

The complexation process of uranyl(Ⅵ) with trioctylphosphine oxide (TOPO) in trimethyl-butylammonium bis (trifluoromethylsulfonyl) imide (N₄₁₁₁NTf₂) was investigated by cyclic voltammetry and IR and UV-vis spectrometry. The complex shows a vibronic progression with an average interval of (728±9)cm^-1 in its UV-vis spectrum. While the asymmetric stretching vibration frequency (ν_as) of the complex is 926cm^-1 in its infrared spectrum. Two successive one-electon tranfer steps take place in the electro reduction process of the ［UO₂(TOPO)₄］²⁺, with the corresponding reduction peak potentials of E_pc1=-1.37V and E_pc2=-1.75V （vs. Ag⁺/Ag）. The first electron transfer step is quasi-reversible while the latter one is irreversible. The half wave potential of the quasi-reversible process of U(Ⅵ)→U(Ⅴ) is -1.33V, which is stable with respect to changes in scan speed and temperature. That implies the stablity of the process and the reduction product. The activation energy of the U(Ⅵ)→U(Ⅴ) reaction is calculated as (39.0±1.1)kJ/mol. The system may possess potential application prospect in the electroseparation process with ionic liquid.