Tunable enforced cavities inside self-assembled capsules

Maehara, Takeshi; Sekiya, Ryo; Harada, Kentaro; Haino, Takeharu

doi:10.1039/c9qo00010k

Cited by 10 publications

(22 citation statements)

References 39 publications

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“…The chain lengths of the extended conformations of G1–G5 , which was defined as the distance between the acetoxy methyl carbons, were calculated by the MacroModel Ver. 9.0 program using the MMFFs force field and are summarized in Table . The extended conformations are the conformations in which all carbon–carbon bonds have antiperiplanar conformations.…”

Section: Results and Discussionsupporting

confidence: 58%

“…Our group has developed resorcinarene-based dimeric capsules capable of capturing molecules terminated with acetoxy groups. − Figure b illustrates resorcinarene-based capsule 1 generated by covalent linking of two cavitands by olefin metathesis . This hemicarcerand has a cavity that can be regulated by metal complexation to the 2,2′-bipyridyl units.…”

Section: Introductionmentioning

confidence: 99%

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Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside a Size-Regulable Hemicarcerand

2021

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A resorcinarene-based hemicarcerand, which consists of two cavitands covalently linked to each other by four alkyl chains, allows structural expansion and contraction by demetalation and metalation of Cu(I) cations with a size change of approximately 12 Å. This metal-mediated switching of the two states regulates the conformations of acetoxy group-terminated alkyl chains. A guest binding study reveals the encapsulation of heptyl to undecyl chains in metal-free and Cu(I)-coordinated capsules. The chemical shifts of the acetoxy groups of the bound guests are the same in the metal-free capsule, while those in the Cu(I)-coordinated one differ from each other. This indicates that the metalfree capsule regulates its size to the bound guests, while the bound guests adopt their conformations to the cavity of the Cu(I)-coordinated capsules. 1 H NMR measurements and molecular mechanics calculations suggest that the bound guests have extended conformations in the metal-free capsule, while the Cu(I)-coordinated capsule forces the bound guests to adopt folded conformations. The presence of folded conformations is supported by the conformational study with structurally similar capsules and a nonsymmetric guest, allowing us to observe nuclear Overhauser effects stemming from the folded conformations of the guest in the cavity.

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Section: Results and Discussionsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside a Size-Regulable Hemicarcerand

2021

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“…The dihedrala ngles of the bipyridyl arms of the methyl-and p-methoxyphenyl-substituted capsules were determined by single-crystal XRD to be 98.6 and 124.48,r espectively. [34,35] The UV/Vis absorption spectra of 2 and 3 showed MLCT bands at l max = 450 nm for 2 and 456 nm for 3 ( Figure 3b), both of which were similar to the MLCT band of the methyl-substituted capsule. Hence, the trans form was likelyt obef ormed by olefin metathesis.…”

Section: Resultsmentioning

confidence: 69%

“…[31] Although thesee xamples nicelys howed the preparation of covalently linked molecular architectures,t hose capable of contraction and expansion of their structures by externals timuli or speciesc oncomitant with switching of molecular recognition capabilities remain less explored. [32,33] Recently,w edemonstrated that substituents on the 6'-positions of 2,2'-bipyridyl arms on the wide rim of resorcinarenebasedc apsules regulate the size of the inner cavity; [34] a p-methoxyphenyl-substituted capsule expanded the cavityb ya pproximately 2 compared with its methyl-substitutedc ounterpart. This expansion is caused by interactions between the electron-rich p-methoxyphenyl group and the electron-deficient bipyridyl arm distortingthe coordination environments of the four metal centers.…”

Section: Introductionmentioning

confidence: 99%

A Regulable Internal Cavity inside a Resorcinarene‐Based Hemicarcerand

Harada

Sekiya

Haino

2020

Chemistry A European J

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Covalent organic capsules, such as carcerands and hemicarcerands, are an interesting class of molecular hosts. These container molecules have confined spaces capable of hostingsmall molecules, although the fact that the size of the inner cavities cannot be changed substantially limits the scope of their applications. The title covalently linked container was produced by metal-directed dimerizationo faresorcinarene-based cavitand having four 2,2'-bipyridyl arms on the wide rim followed by olefin metathesis at the vertices of the resultingc apsulew ith as econd-generation Grubbs catalyst. The covalently linked bipyridyl arms permit expansion of the inner cavity by demetalation. This structural changei nfluences the molecular recognition properties;t he metal-coordinated capsule recognizes only 4,4'-diacetoxybi-phenyl,w hereas the metal-free counterpart can encapsulate not only 4,4'-diacetoxybiphenyl, but also 2,5-disubstituted-1,4-bis(4-acetoxyphenylethynyl)benzene, which is 9.4 longert han the former guest. Molecular mechanics calculations predict that the capsulee xpands the internal cavity to encapsulate the long guest by unfolding the folded conformationo ft he alkyl chains, which demonstrates the flexible and regulable nature of the cavity.Guest competitionexperimentss how that the preferred guest can be switched by metalation and demetalation. This external-stimuli-responsive guest exchange can be utilizedf or the development of functional supramolecular systems controlling the uptake, transport, and releaseo fchemicals.

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“…These coordinating 2,2′-bipyridyl arms function as hinges; consequently, the enforced cavity can be expanded or contracted by widening or narrowing the dihedral angle of the 2,2′-bipyridyl arms (Figure 10). 32 Analysis of the crystal structures of 1Cu a and 1Cu b revealed that the dihedral angle of the methyl-substituted capsule 1Cu a was 81.4°, whereas that of the p-methoxyphenyl-substituted capsule 1Cu b was 124°. The p-methoxybenzene rings were nearly coplanar to the 2,2′-bipyridyl arms, probably as a result of donor-acceptor - stacking interactions.…”

Section: Tuning the Cavity Interiormentioning

confidence: 99%

Resorcinarene-Based Supramolecular Capsules: Supramolecular Functions and Applications

Sekiya

Harada

Nitta

et al. 2021

Synlett

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A resorcinarene is a synthetic macrocycle comprising four resorcinol molecules covalently linked by methylene bridges. The interannular bridges produce a cavitand, which possesses a bowl-shaped structure. We have developed supramolecular capsules formed through Ag(I) and Cu(I) coordination-driven self-assembly of cavitands possessing 2,2’-bipyridyl arms at the upper rim. The self-assembled capsules accommodate various molecular guests and supramolecular assemblies possessing acetoxy groups. The host-guest chemistry of the molecular capsules is applied to fabricate supramolecular polymers. This account describes the recent developments in supramolecular chemistry of resorcinarene-based coordination capsules and describes the brief history of resorcinarene-based capsules and related capsules.

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Tunable enforced cavities inside self-assembled capsules

Abstract: Controlling and tuning the molecular recognition properties is a crucial task in host–guest chemistry.

Cited by 10 publications

References 39 publications

Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside a Size-Regulable Hemicarcerand

Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside a Size-Regulable Hemicarcerand

A Regulable Internal Cavity inside a Resorcinarene‐Based Hemicarcerand

Resorcinarene-Based Supramolecular Capsules: Supramolecular Functions and Applications

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