An Insight into Adaptive Deformation of Rigid Cucurbit[6]uril Host in Symmetric [2]Pseudorotaxanes

Li, Fei-ze; Mei, Lei; Wu, Qinghe; Yin, Tian; Hu, Kexin; Ge, Yun‐chen; Liu, Ning; Gibson, John K.; Chai, Zhifang; Shi, Wei‐Qun

doi:10.1002/ejoc.201800964

Cited by 5 publications

(11 citation statements)

References 63 publications

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“…Variable Conformations of C8BPCA@CB [6] in URCPs. In our previous study, 47 we have confirmed that the binding constant between CB [6] and the string guest becomes weaker when the chain length is longer than C6. As revealed by the results of 1 H NMR spectra, it is expected that C8BPCA@ CB [6] should have higher flexibility in the assembly process with metal cations, i.e., both the string guest and macrocyclic host can show a higher degree of freedom.…”

Section: ■ Experimental Sectionsupporting

confidence: 67%

“…In Figure , a relatively less downfield shift and a weaker deshielding effect of the H a proton are observed for C8BPCEt @CB[6], suggesting that the C8 chain is more loosely encapsulated by CB[6] and can show more flexibility than C6 and C7 chains. In combination with the lowest binding constant of the three host–guest systems reported in previous work, we can speculate that the flexibility originating from the weak binding strength between CB[6] and the C8 chain will endow a related pseudorotaxane ligand with more diverse conformations during the assembly process with uranyl, which is favorable for the construction of complicated URCPs.…”

Section: Results and Discussionmentioning

confidence: 72%

“…As shown in Figure , molecular conformations of the pseudorotaxane ligands show an obvious difference in different URCPs given from C8BPCA @CB[6] and uranyl. For URCP1 and URCP3 , the configurations of the pseudorotaxane ligand maintain high similarity to that of the C8BPCA @CB[6] ligand, and the guest molecule bridged by the C8 chain has a strict trans- configuration. However, in order to meet the coordination requirements with the uranyl center, CB[6] molecules in these two URCPs still rotated to some extent, and their relative positions are slightly different from that in the pristine C8BPCA @CB[6] ligand.…”

Section: Results and Discussionmentioning

confidence: 99%

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Kinked-Helix Actinide Polyrotaxanes from Weakly Bound Pseudorotaxane Linkers with Variable Conformations

Mei

et al. 2020

Inorg. Chem.

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The incorporation of a mechanically interlocked molecule such as pseudorotaxane into metal−organic coordination polymers has afforded plenty of new hybrid materials with special structures and unique properties. In this work, we employ a weakly bound cucurbit[6]uril (CB[6])-bipyridinium pseudorotaxane as a supramolecular precursor to assemble with uranyl, aiming to construct uranyl-rotaxane coordination polymers (URCPs) with intriguing structures. By adjusting the synthetic conditions, a new kinked-helix uranyl rotaxane compound (URCP3), together with three other compounds URCP1, URCP2, and URCP4 varying from 1D chains to 2D interwoven networks, was obtained. Detailed structural analyses indicate that the pseudorotaxane ligand (C8BPCA@CB[6]) shows great configuration diversity in the construction of URCPs, which is most probably due to the weak binding strength between the host and guest molecules. Specifically, based on the monodentate coordination of the end carboxyl groups of C8BPCA forced by the surrounding unilaterally-chelated oxalate, the entire flexible pseudorotaxane linker will be more likely to undergo conformational change, thereby binding to the uranyl center from both sides of the uranyl equatorial plane and promoting the formation of a kinked helix structure of URCP3 that is shaped like a Chinese knot along [001]. This work enriches the library of actinide-rotaxane compounds and provides a new approach to construct metal−organic compounds with complicated structures using weakly bonded pseudorotaxanes as well.

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Section: ■ Experimental Sectionsupporting

confidence: 67%

Section: Results and Discussionmentioning

confidence: 72%

Section: Results and Discussionmentioning

confidence: 99%

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Kinked-Helix Actinide Polyrotaxanes from Weakly Bound Pseudorotaxane Linkers with Variable Conformations

Mei

et al. 2020

Inorg. Chem.

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“…Because of the radioactive and chemical toxicity of uranium, strict care and protection should be employed in related operations. C6BPCN3 and CB [6] were synthesized according to the previous report, 31 and were preassembled in aqueous solution to give the pseudorotaxane precursor, i.e., C6BPCN3@ CB [6] (see SI for more details). Uranyl nitrate [UO 2 (NO 3 ) 2 •6H 2 O] was dissolved in deionized water to give 0.5 M uranyl solutions.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Proximity Effect in Uranyl Coordination of the Cucurbit[6]uril-Bipyridinium Pseudorotaxane Ligand for Promoting Host–Guest Synergistic Chelating

Geng

et al. 2021

Inorg. Chem.

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In the present work, we proposed regulating uranyl coordination behavior of cucurbituril-bipyridinium pseudorotaxane ligand by utilizing meta-functionalized bipyridinium dicarboxylate guest. A tailored pseudorotaxane precursor involving 1,1′-(hexane-1,6-diyl)bis(3-cyanopyridin-1-ium) bromide (C6BPCN3) and cucurbit[6]uril (CB[6]) has designed and synthesized. Through in situ hydrolysis of the pseudorotaxane ligands and their coordination assembly with uranyl cations, seven new uranyl-rotaxane coordination polymers URCP1–URCP7 have been obtained under hydrothermal conditions in the presence of different anions. It is demonstrated that the variation of carboxylate groups from para- to meta-position greatly affected the coordination behaviors of the meta-functionalized pseudorotaxane linkers, which are enriched from simple guest-only binding to host–guest simultaneous coordination and synergistic chelating. This effective regulation on uranyl coordination of supramolecular pseudorotaxane can be attributed to the proximity effect, which refers to the meta-position carboxyl group being spatially closer to the portal carbonyl group of CB[6]. Moreover, by combining other regulation methods such as introducing competing counterions and modulating solution acidity, the nuclearity of the uranyl center and the coordination patterns of the pseudorotaxane ligand can be diversely tuned, which subsequently exert great influence on the final dimensionality of resultant uranyl compounds. This work presents a large diversity of uranyl-based coordination polyrotaxane compounds with fascinating mechanically interlocked components and, most importantly, provides a feasible approach to adjust and control the metal coordination behavior of the pseudorotaxane ligand that might expand the scope of application of such supramolecular ligands.

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“…It can be taken as an adaptive reconstruction of C7BPy to diminish the steric hindrance around the uranyl equatorial plane. When the spacer length is longer as C8, the binding strength of host‐guest inclusion between C8BPy and CB[6] is further weakened [ K =(4.50±0.75)×10 3 ] [9b,12] …”

Section: Resultsmentioning

confidence: 99%

Temperature‐Triggered Structural Dynamics of Non‐Coordinating Guest Moieties in a Fluorescent Actinide Polyrotaxane Framework

Geng

et al. 2021

Chemistry A European J

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We present here the synthesis of a novel fluorescent actinide polyrotaxane compound URCP1 through the utilization of an end‐cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non‐coordinating guest motif in the obtained polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature‐triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature‐triggered structural dynamics in URCP1 represents the first report of actinide polyrotaxane with such feature in solid‐state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4×10−3 ppm.

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An Insight into Adaptive Deformation of Rigid Cucurbit[6]uril Host in Symmetric [2]Pseudorotaxanes

Cited by 5 publications

References 63 publications

Kinked-Helix Actinide Polyrotaxanes from Weakly Bound Pseudorotaxane Linkers with Variable Conformations

Kinked-Helix Actinide Polyrotaxanes from Weakly Bound Pseudorotaxane Linkers with Variable Conformations

Proximity Effect in Uranyl Coordination of the Cucurbit[6]uril-Bipyridinium Pseudorotaxane Ligand for Promoting Host–Guest Synergistic Chelating

Temperature‐Triggered Structural Dynamics of Non‐Coordinating Guest Moieties in a Fluorescent Actinide Polyrotaxane Framework

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