Coordination Polymers of Cucurbit[n]urils with Metal Ions - Supramolecular Assemblies of Cucurbit[n]urils with Metal Ions - page 79

3.6 Induced Coordination Polymers of Cucurbit[ n > 8]uril
with Metal Ions

The largest Q[n] family member, tQ[14], with 14 glycoluril units linked by 28
methylene bridges [ 61 ], has recently been reported by the authors' Quizhou group.
This molecule has a twisted figure-eight structure and thus does not contain a
bowl-shaped cavity of the type present in the other Q[ n ] molecules discussed so
far. Reaction of a selection of Ln 3 + ions with tQ[14] in 6 mol/L HCl in the pres-
ence of [CdCl 4 ] 2 − , interestingly only afforded isolated tQ[14] complexes with
Eu 3 + . The X-ray structure of [Eu 2 (H 2 O) 7 Cl(tQ[14])]Cl 5 66H 2 O showed the pres-
ence of enantiomeric pairs in the crystal (Fig. 3.40 a, b). In addition, a pair of 1D
coordination polymers in which each tQ[14] is coordinated to three Eu 3 + cations
was also obtained (Fig. 3.40 c). These experimental results suggest that the novel
tQ[14] could selectively coordinate certain lanthanide cations and yield crystals
with novel supramolecular assemblies.
Although, there is only one example of polydimensional coordination polymers
of cucurbit[ n > 8]uril (Q[ n > 8]) with metal ions at this stage, it could mainly be
because of the difficulties in synthesis or isolation sufficient amounts of Q[ n > 8],
such as Q[10] and tQ[14]. However, we believe that their coordination chemistry
will gradually develop in the future.

Fig. 3.40 X-ray crystal structure of the two enantiomers of the Eu 3 + -tQ[14] complex: a side

view, b top view; and c a pair of 1D coordination polymers incorporating tQ[14] molecules and
Eu 3 + cations