A Regulable Internal Cavity inside a Resorcinarene‐Based Hemicarcerand

Harada Kentaro

Sekiya Ryo

Haino Takeharu

Chemistry A European Journal

Covalent organic capsules, such as carcerands and hemicarcerands, are an interesting class of molecular hosts. These container molecules have confined spaces capable of hosting small 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 dimerization of a resorcinarene‐based cavitand having four 2,2′‐bipyridyl arms on the wide rim followed by olefin metathesis at the vertices of the resulting capsule with a second‐generation Grubbs catalyst. The covalently linked bipyridyl arms permit expansion of the inner cavity by demetalation. This structural change influences the molecular recognition properties; the metal‐coordinated capsule recognizes only 4,4′‐diacetoxybiphenyl, whereas 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 Å longer than the former guest. Molecular mechanics calculations predict that the capsule expands the internal cavity to encapsulate the long guest by unfolding the folded conformation of the alkyl chains, which demonstrates the flexible and regulable nature of the cavity. Guest competition experiments show that the preferred guest can be switched by metalation and demetalation. This external‐stimuli‐responsive guest exchange can be utilized for the development of functional supramolecular systems controlling the uptake, transport, and release of chemicals.

hemicarcerands

host–guest systems

molecular recognition

resorcinarenes

supramolecular chemistry

eng

Wiley

This is the peer reviewed version of the following article: K. Harada, R. Sekiya, T. Haino, Chem. Eur. J. 2020, 26, 5810, which has been published in final form at https://doi.org/10.1002/chem.201905805. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

This is not the published version. Please cite only the published version. この論文は出版社版ではありません。引用の際には出版社版をご確認、ご利用ください。

[ISSN] 0947-6539

[ISSN] 1521-3765

[DOI] 10.1002/chem.201905805

[DOI] https://doi.org/10.1002/chem.201905805