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Kinetics and Mechanism of Cation‐Induced Guest Release from Cucurbit[7]uril [in press]

Miskolczy, Zsombor; Megyesi, Mónika; Biczók, László; Prabodh, Amrutha; Biedermann, Frank

Abstract:
Abstract: The release of two organic guests from cucurbit[7]uril (CB7) was selectively monitored by the stoppedflow method in aqueous solutions of inorganic salts to reveal the mechanistic picture in detail. Two contrasting mechanisms were identified: The symmetric dicationic 2,7- dimethyldiazapyrenium shows a cation-independent complex dissociation mechanism coupled to deceleration of the ingression in the presence of alkali and alkaline earth cations (M$^{+n}$) due to competitive formation of CB7–M$^{+n}$ complexes. A much richer, unprecedented kinetic behaviour was observed for the ingression and egression of the monocationic and non-symmetric berberine (B$^{+}$). The formation of ternary complex B+–CB7–M$^{+n}$ was unambiguously revealed. A difference of more than two orders of magnitude was found in the equilibrium constants of Mn+ binding to B$^{+}$–CB7 inclusion complex. Large cations, such as K$^{+}$ and Ba$^{2+}$, also promoted B$^{+}$ expulsion from the ternary complex in a bimolecular process. This study reveals a previously hidden mechanistic picture and motivates systematic kinetic investigations of other host–guest systems.

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Verlagsausgabe §
DOI: 10.5445/IR/1000119942
Veröffentlicht am 03.06.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Nanotechnologie (INT)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 0947-6539, 1521-3765
KITopen-ID: 1000119942
HGF-Programm 43.21.04 (POF III, LK 01)
Molecular Engineering
Erschienen in Chemistry - a European journal
Vorab online veröffentlicht am 13.01.2020
Nachgewiesen in Scopus
Web of Science
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