Issue 4, 2021

Orientation of the α-CD component of [2]rotaxanes affects their specific molecular recognition behaviour

Abstract

In this study we synthesized a pair of orientationally isomeric [2]rotaxanes (1 and 2) featuring an α-cyclodextrin (α-CD) as the macrocyclic component and phenylurea and 2-hydroxybenzophenone moieties as stoppers of the axle-like component. The presence of the α-CD component enhanced the anion recognition ability of the urea unit in isomer 1, with the OH groups on the wide rim of α-CD undergoing hydrogen bonding with the anions. The association constant for the interaction between 1 and the acetate (AcO) anion was more than four times that of the corresponding non-interlocked dumbbell-shaped molecule and the AcO anion. The other isomer 2, in which the wide rim of the α-CD component faced the 2-hydroxybenzophenone unit, was preferentially deprotonated by the AcO anion to give the phenoxide anion, which was stabilized through noncovalent interactions with the OH groups on the wide rim of the α-CD unit in an organic solvent; in contrast, the AcO anion did not deprotonate the corresponding non-interlocked dumbbell-shaped molecule.

Graphical abstract: Orientation of the α-CD component of [2]rotaxanes affects their specific molecular recognition behaviour

Supplementary files

Article information

Article type
Research Article
Submitted
28 Oct 2020
Accepted
25 Nov 2020
First published
26 Nov 2020

Org. Chem. Front., 2021,8, 676-685

Orientation of the α-CD component of [2]rotaxanes affects their specific molecular recognition behaviour

T. Iwamoto, S. Miyagawa, M. Naito and Y. Tokunaga, Org. Chem. Front., 2021, 8, 676 DOI: 10.1039/D0QO01337D

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