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Catalysis in a cationic coordination cage using a cavity-bound guest and surface-bound anions : inhibition, activation, and autocatalysis
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Cullen, William, Metherell, Alexander J., Wragg, Ashley B., Taylor, Christopher G. P., Williams, Nicholas H. and Ward, Michael D. (2018) Catalysis in a cationic coordination cage using a cavity-bound guest and surface-bound anions : inhibition, activation, and autocatalysis. Journal of the American Chemical Society, 140 (8). pp. 2821-2828. doi:10.1021/jacs.7b11334 ISSN 1520-5126.
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Official URL: http://doi.org/10.1021/jacs.7b11334
Abstract
The Kemp elimination (reaction of benzisoxazole with base to give 2-cyanophenolate) is catalyzed in the cavity of a cubic M8L12 coordination cage because of a combination of (i) benzisoxazole binding in the cage cavity driven by the hydrophobic effect, and (ii) accumulation of hydroxide ions around the 16+ cage surface driven by ion-pairing. Here we show how reaction of the cavity-bound guest is modified by the presence of other anions which can also accumulate around the cage surface and displace hydroxide, inhibiting catalysis of the cage-based reaction. Addition of chloride or fluoride inhibits the reaction with hydroxide to the extent that a new autocatalytic pathway becomes apparent, resulting in a sigmoidal reaction profile. In this pathway the product 2-cyanophenolate itself accumulates around the cationic cage surface, acting as the base for the next reaction cycle. The affinity of different anions for the cage surface is therefore 2-cyanophenolate (generating autocatalysis) > chloride > fluoride (which both inhibit the reaction with hydroxide but cannot deprotonate the benzisoxazole guest) > hydroxide (default reaction pathway). The presence of this autocatalytic pathway demonstrates that a reaction of a cavity-bound guest can be induced with different anions around the cage surface in a controllable way; this was confirmed by adding different phenolates to the reaction, which accelerate the Kemp elimination to different extents depending on their basicity. This represents a significant step toward the goal of using the cage as a catalyst for bimolecular reactions between a cavity-bound guest and anions accumulated around the surface.
Item Type: | Journal Article | |||||||||||||||
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Subjects: | Q Science > QD Chemistry | |||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | |||||||||||||||
SWORD Depositor: | Library Publications Router | |||||||||||||||
Library of Congress Subject Headings (LCSH): | Coordination compounds, Catalysis, Chemical bonds, Hydroxides, Anions | |||||||||||||||
Journal or Publication Title: | Journal of the American Chemical Society | |||||||||||||||
Publisher: | American Chemical Society (ACS) | |||||||||||||||
ISSN: | 1520-5126 | |||||||||||||||
Official Date: | 28 February 2018 | |||||||||||||||
Dates: |
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Volume: | 140 | |||||||||||||||
Number: | 8 | |||||||||||||||
Page Range: | pp. 2821-2828 | |||||||||||||||
DOI: | 10.1021/jacs.7b11334 | |||||||||||||||
Status: | Peer Reviewed | |||||||||||||||
Publication Status: | Published | |||||||||||||||
Reuse Statement (publisher, data, author rights): | ** From Crossref via Jisc Publications Router. | |||||||||||||||
Access rights to Published version: | Restricted or Subscription Access | |||||||||||||||
Date of first compliant deposit: | 1 March 2018 | |||||||||||||||
Date of first compliant Open Access: | 7 February 2019 | |||||||||||||||
RIOXX Funder/Project Grant: |
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