Cramming versus threading of long amphiphilic oligomers into a polyaromatic capsule

Oligo(ethylene oxide)s are known as widely useable yet not very interactive amphiphilic compounds. Here we report that the long amphiphilic oligomers are bound by a polyaromatic capsule in two different manners, depending on the chain length. For instance, the shorter pentamer is crammed into the is...

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Bibliographic Details
Published in:Nature communications 2018-10, Vol.9 (1), p.4227-10, Article 4227
Main Authors: Yamashina, Masahiro, Kusaba, Shunsuke, Akita, Munetaka, Kikuchi, Takashi, Yoshizawa, Michito
Format: Article
Language:English
Subjects:
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639/638/541
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639/638/541/965
Calorimetry
Crystal structure
Ethylene oxide
Humanities and Social Sciences
Hydrogen
Hydrogen bonding
Mass spectrometry
Molecular weight
multidisciplinary
NMR
Nuclear magnetic resonance
Oligomers
Science
Science (multidisciplinary)
Scientific imaging
Titration
Titration calorimetry
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Summary:Oligo(ethylene oxide)s are known as widely useable yet not very interactive amphiphilic compounds. Here we report that the long amphiphilic oligomers are bound by a polyaromatic capsule in two different manners, depending on the chain length. For instance, the shorter pentamer is crammed into the isolated cavity of the capsule, whereas the longer decamer is threaded into the capsule to form a 1:1 host–guest complex in a pseudo-rotaxane fashion. These unusual bindings occur instantly, spontaneously, and quantitatively even in water at room temperature, with relatively high binding constants ( K a  > 10 6  M –1 ). Isothermal titration calorimetry (ITC) studies reveal that enthalpic stabilization is a dominant driving force for both of the complexations through multiple host–guest CH-π and hydrogen-bonding interactions. Furthermore, long oligomers with an average molecular weight of 1000 Da (e.g., 22-mer) are also threaded into the capsules to give pseudo-rotaxane-shaped 2:1 host–guest complexes in water, selectively. Molecular capsules typically bind only guests with volumes smaller than their cavities. Here, the authors find that a polyaromatic capsule accommodates linear amphiphilic oligomers in a length-dependent manner, whereas short chains are fully crammed into the cavity, long chains can be incorporated into the capsule in a threaded fashion.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-018-06458-w