The spectroscopic and electrochemical behavior of the complex of tetraalkylurea ligands with uranyl(VI) and europium(III) in ionic liquid 1-butyl-3-methylimidazolium bis(tri-fluoromethylsulfonyl)imide ([Bmim][NTf2]) was studied. As the steric hindrance of the substituent increases, the number of ligands in the [UO2(L)n]2+ complex decreases, however, Eu(III) maintains 8-coordinated complexes [Eu(L)8]3+. The effect of urea ligands on the redox potential of Eu(III) is significantly greater than that of UO22+. Tetrabutylurea can better stabilize the low-valence Eu(II) and improve the redox reversibility of UO22+.

中文翻译：

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离子液体中尿素配体与铀酰 (VI) 和铕 (III) 配合物的光谱和电化学研究

研究了四烷基脲配体与铀酰（VI）和铕（III）在离子液体 1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰基）亚胺（[Bmim][NTf2]）中的光谱和电化学行为。随着取代基的空间位阻增加，[UO2(L)n]2+ 复合物中的配体数量减少，但 Eu(III) 保持 8 配位复合物 [Eu(L)8]3+。尿素配体对Eu(III)氧化还原电位的影响明显大于UO22+。四丁基脲可以更好地稳定低价Eu(II)并提高UO22+的氧化还原可逆性。