Potential Applications of Q[n]-Based Coordination Complexes and Polymers - Supramolecular Assemblies of Cucurbit[n]urils with Metal Ions - page 87

Fig. 4.4 EDS of the representative products isolated from Ln 3 +

light − Ln 3 heavy − SPMeQ [ 5 ]

− CDCL 2 − HCL systems mixtures with 1:1 Ln 3 +

light : Ln 3 heavy ratios (unpublished)

are occupied by Ln 3 + -Q[6] linear coordination polymers (Figs. 3.21 and 4.5 ). The
most remarkable phenomenon was the rapid precipitation of Ln 3 + -Q[6]-[CdCl 4 ] 2 −
or -[ZnCl 4 ] 2 − systems when the Ln 3 + cations were La, Ce, Pr, or Nd. This may
offer a means to separate the light lanthanides cations from their heavier counter-
parts. When a solution of Q[6] in aqueous HCl was added to mixtures of light and
heavy lanthanides in a 1:1 ratio, for example La:Eu, in aqueous HCl solution, a large
amount of white precipitate was again deposited. EDS showed that in terms of cations
the white precipitate contained ~90 % La and ~10 % Eu, suggesting a strategy for the
separation of light lanthanides from their heavier counterparts (Fig. 4.5 ) [ 10 ].
We have recently investigated the coordination of (HO) 10 Q[5] molecules with a
series of Ln 3 + cations in the presence of potassium salt of [PMo 12 O 40 ] 3 − anion. The
results, mainly based on X-ray diffraction analysis, have revealed that the K + /Ln 3 + /
(HO) 10 Q[5]/[PMo 12 O 40 ] 3 − systems result in the formation of three different supra-
molecular assembly isomorphous groups with increasing atomic number of lantha-
nides, in particular, the complexes and corresponding supramolecular assemblies
contain lighter lanthanide cations which coordinate to (HO) 10 Q[5] molecules in
solid state for the first two isomorphous groups, while the solid crystals involving
heavy lanthanide systems show no heavier lanthanide cations, which still stay in the
solution state. Such difference offers a possible means to separate the lighter lantha-
nide cations from their heavier counterparts. Figure 4.6 shows these representative