As an emerging type of actinide hybrid
material, uranyl–rotaxane coordination polymers (URCPs) with
new coordination patterns and topological structures are still desired.
In this work, we propose a new strategy to construct URCPs by promoting
the simultaneous coordination of both the wheel and axle moieties
in pseudorotaxane linkers with metal nodes. Starting from a series
of cucurbit[6]uril (CB[6])-based pseudorotaxane ligands, CnBPCA@CB[6] [CnBPCA = 1,1-(α,ω-diyl)bis[4-(ethoxycarbonyl)pyridin-1-ium]
bromides, where n = 5–8] with slightly deformed
CB[6], four new URCPs (URCP1, URCP3, URCP4, and URCP5) with interwoven network structures,
as well as another noninterwoven polymer(URCP2), have
been successfully prepared. According to single-crystal structure
analysis, we attribute the interwoven structures of the URCPs to the
distortion of CB[6] in pseudorotaxane ligands with shorter or longer
spacers (C5, C7, and C8). This indicates that the deformation could
effectively diminish the steric hindrance around the portals, thus
endowing the “inert” CB[6] host with coordination ability
like the string molecule. Besides, the participation of water molecules
and sulfate anions in the uranyl coordination sphere is also found
to have a great influence on the final structures of the obtained
URCPs. The successful preparation of interwoven URCPs in this work
gives some new insights into the metal coordination of supramolecular
entities and could facilitate other new applications of CB[6]-based
pseudorotaxane ligands. Most importantly, the strategy proposed in
this work provides some hints in the controllable design of metal–organic
rotaxane frameworks with unique topologies.
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