Determination of the kinetics underlying the pKa shift for the 2-aminoanthracenium cation binding with cucurbit[7]uril

The binding dynamics of the 2-aminoanthracenium cation (AH(+)) and 2-aminoanthracene (A) with cucurbit[7]uril (CB[7]) was studied using stopped-flow experiments. The kinetics was followed by measuring the fluorescence changes over time for AH(+) and A, which emit at different wavelengths. The studie...

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Bibliographic Details
Published in:Faraday discussions 2015, Vol.185, p.381-398
Main Authors: Thomas, Suma S, Bohne, Cornelia
Format: Article
Language:English
Subjects:
Amines - chemistry
Anthracenes - chemistry
Bridged-Ring Compounds - chemistry
Cations - chemistry
Hydrogen-Ion Concentration
Imidazoles - chemistry
Kinetics
Molecular Structure
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Summary:The binding dynamics of the 2-aminoanthracenium cation (AH(+)) and 2-aminoanthracene (A) with cucurbit[7]uril (CB[7]) was studied using stopped-flow experiments. The kinetics was followed by measuring the fluorescence changes over time for AH(+) and A, which emit at different wavelengths. The studies at various pH values showed different mechanisms for the formation of the AH(+)@CB[7] complex, with this complex formed either by the binding of AH(+) or by the initial binding of A followed by protonation. In the latter case, it was possible to determine the protonation ((1.5 ± 0.4) × 10(9) M(-1) s(-1)) and deprotonation (89 ± 7 s(-1)) rate constants for complexed A/AH(+), which showed that the pKa shift of +3.1 for A/AH(+) in the complex is mainly due to a lower deprotonation rate constant.
ISSN:1359-6640
DOI:10.1039/c5fd00095e