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Spacer Length-Independent Shuttling of the Pillar[5]arene Ring in Neutral [2]Rotaxanes.

ABSTRACT: For a series of neutral [2]rotaxanes consisting of a pillar[5]arene ring and axles possessing two stations separated by flexible spacers of different lengths, the free energies of activation for the ring shuttling between the stations were found to be independent of the spacer length. The constitution of the spacer affects the activation energies: replacement of CH₂ groups by repulsive oxygen atoms in the axle increases the barrier. The explanation for the observed length-independence lies in the presence of a barrier for re-forming the stable co-conformation, which makes the ring travel back and forth along the thread in an intermediate state.

SUBMITTER: Ogoshi T

PROVIDER: S-EPMC5947626 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Spacer Length-Independent Shuttling of the Pillar[5]arene Ring in Neutral [2]Rotaxanes.

Ogoshi Tomoki T Kotera Daisuke D Nishida Shungo S Kakuta Takahiro T Yamagishi Tada-Aki TA Brouwer Albert M AM

Chemistry (Weinheim an der Bergstrasse, Germany) 20180308 24

For a series of neutral [2]rotaxanes consisting of a pillar[5]arene ring and axles possessing two stations separated by flexible spacers of different lengths, the free energies of activation for the ring shuttling between the stations were found to be independent of the spacer length. The constitution of the spacer affects the activation energies: replacement of CH<sub>2</sub> groups by repulsive oxygen atoms in the axle increases the barrier. The explanation for the observed length-independence ...[more]

PMID: 29473232

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