Determination of the kinetics underlying the pK sub(a) shift for the 2-aminoanthracenium cation binding with cucurbit[7]uril

The binding dynamics of the 2-aminoanthracenium cation (AH super(+)) 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 super(+) and A, which emit at different wavelengths...

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Bibliographic Details
Published in:Faraday discussions 2015-12, Vol.185, p.381-398
Main Authors: Thomas, Suma S, Bohne, Cornelia
Format: Article
Language:English
Subjects:
Binding
Cations
Dynamic tests
Emittance
Fluorescence
Protonation
Rate constants
Wavelengths
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Summary:The binding dynamics of the 2-aminoanthracenium cation (AH super(+)) 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 super(+) and A, which emit at different wavelengths. The studies at various pH values showed different mechanisms for the formation of the AH super(+)B[7] complex, with this complex formed either by the binding of AH super(+) or by the initial binding of A followed by protonation. In the latter case, it was possible to determine the protonation ((1.5 plus or minus 0.4) 10 super(9) M super(-1) s super(-1)) and deprotonation (89 plus or minus 7 s super(-1)) rate constants for complexed A/AH super(+), which showed that the pK sub(a) shift of +3.1 for A/AH super(+) in the complex is mainly due to a lower deprotonation rate constant.
ISSN:1359-6640
1364-5498
DOI:10.1039/c5fd00095e