Adducts of aqua complexes of Ln3+ with a symmetrical octamethyl-substituted cucurbituril: potential applications for isolation of heavier lanthanides |
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| Authors: | Xin Yu Li-Mei Zheng Yun-Qian Zhang Sai-Feng Xue Zhu Tao |
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| Institution: | 1. Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, P.R. China;2. School of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou 450001, P.R. China |
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| Abstract: | Interaction of a series of lanthanide cations (Ln3+) with a symmetrical octamethyl-substituted cucurbituril (OMeQ6]) has been investigated. X-ray single-crystal diffraction analysis has revealed that the interaction results in the formation of adducts of OMeQ6] with aqua complexes of lanthanide cations (Ln(H2O)8]3+), Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb in OMeQ6]–Ln(NO3)3–H2O systems. However, no solid crystals were obtained from systems containing La, Ce, Pr, Nd and Sm. X-ray diffraction analysis has revealed that although the solid adducts fall into two isomorphous groups, there are no significant differences in the interactions between OMeQ6] and Ln(H2O)8]3+ complexes and in the corresponding supramolecular assemblies. Thermodynamic parameters for the interaction between OMeQ6] and Ln(H2O)8]3+ complexes based on isothermal titration calorimetry experiments show two periods corresponding to the above two systems, with the lighter lanthanide cations preferring to remain in solution and the heavier lanthanide cations forming crystalline solids. Electron spectroscopy has shown that interaction of OMeQ6] with lanthanide cations could provide a means of isolating heavier lanthanide cations from their lighter counterparts. |
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| Keywords: | octamethyl-substituted cucurbituril lanthanide aqua complexes adducts isolation |
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