Miskolczy, Zsombor and Megyesi, Mónika and Biczók, László and Prabodh, Amrutha and Biedermann, Frank (2020) Kinetics and Mechanism of Cation-Induced Guest Release from Cucurbit[7]uril. CHEMISTRY-A EUROPEAN JOURNAL, 26 (33). pp. 7433-7441. ISSN 0947-6539 (print); 1521-3765 (online)
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Abstract
The release of two organic guests from cucurbit[7]uril (CB7) was selectively monitored by the 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-dimethyldiazapyrenium shows a cation-independent complex dissociation mechanism coupled to 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 complex B+-CB7-Mn+ 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 Ba2+, 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.
Item Type: | Article |
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Uncontrolled Keywords: | host–guest systems; kinetics; reaction mechanisms; salt effect; self-assembly |
Subjects: | Q Science / természettudomány > QD Chemistry / kémia > QD02 Physical chemistry / fizikai kémia |
SWORD Depositor: | MTMT SWORD |
Depositing User: | MTMT SWORD |
Date Deposited: | 22 Sep 2020 14:00 |
Last Modified: | 22 Sep 2020 14:00 |
URI: | http://real.mtak.hu/id/eprint/114047 |
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