L. Biczók, Z. Miskolczy, M. Megyesi, A. Prabodh, F. Biedermann, Chem. Eur. J. 2020,  Acccepted Manuscript.

DOI: 10.1002/chem.201905633

 

This publication has been highlighted in the article "Salt-Induced Release from Macrocycles" on chemistryview.org!

 

 

Abstract

The exit of two organic guests from cucurbit[7]uril (CB7) was selectively monitored by stopped?flow method in aqueous solutions of inorganic salts to reveal the mechanistic picture in detail. Two contrasting mechanisms were identified: The symmetric dicationic 2,7?dimethyl?diazapyrenium shows a cation?independent complex dissociation mechanism coupled to a deceleration of the ingression in the presence of alkali and alkaline earth cations (Mn+) due to competitive formation of CB7?Mn+ 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 B+?CB7?Mn+ complex was undoubtedly revealed. More than two orders of magnitude difference were found in the equilibrium constants of Mn+ binding to B+?CB7 inclusion complex. Large cations, such as K+ and Ba2+, promoted B+ expulsion also in a bimolecular process from the ternary complex. This study reveals a priorly hidden mechanistic picture and motivates systematic kinetic investigations of other host?guest systems.