The interactions between a series of lanthanide cations (Ln3+ ) and methyl-substituted cucurbiturils (SPMeQ[5] and SHMeQ[6]) derived from a 3α-methyl glycoluril have been investigated. Single-crystal X-ray diffraction analysis revealed that both SPMeQ[5] and SHMeQ[6] selectively interact with certain lanthanide ions. SPMeQ[5] forms coordination capsules in the presence of [CdCl4 ]2- . The Ln3+ cations that interact are the four light lanthanides, La3+ , Ce3+ , Pr3+ , and Nd3+ , whereas the remaining lanthanide cations remain in solution. SHMeQ[6] formed adducts of SHMeQ[6] with aqua complexes of lanthanide cations ([Ln(H2 O)8 ]3+ ); for SHMeQ[6]-Ln(NO3 )3 -CdCl2 -HCl systems (Ln=Gd-Lu), no solid crystals were obtained from systems that contained La, Ce, Pr, Nd, Sm, or Eu. Whereas solid crystals of adducts of SHMeQ[6] with aqua complexes of lanthanide cations (Ln=Sm-Lu) formed SHMeQ[6]-Ln(NO3 )3 systems in neutral solution, no solid crystals were obtained from systems that contained La, Ce, Pr, or Nd. These results suggest that SPMeQ[5]- and SHMeQ[6]-Ln(NO3 )3 systems could be useful for the selective isolation of these lighter or heavier lanthanide cations from mixtures. Energy-dispersive spectrometry indicated that the lighter or heavier lanthanide cations could be isolated from their heavier or lighter counterparts through interaction with SPMeQ[5] and SHMeQ[6].
Keywords: X-ray diffraction; cations; cucurbiturils; lanthanides; supramolecular chemistry.
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