Determination of the kinetics underlying the pKa shift for the 2-aminoanthracenium cation binding with cucurbit[7]urilElectronic supplementary information (ESI) available: Synthesis and purification of cucurbit[7]uril; model for the fitting of binding isotherms and binding isotherms at different pH values; singlet excited state lifetimes for AH+/A in water and in the presence of CB[7]; kinetics for AH+/A binding to CB[7] and models used for fitting. See DOI: 10.1039/c5fd00095e

• Main Authors: Thomas, Suma S, Bohne, Cornelia
• Format: Article
• ISSN: 1359-6640; 1364-5498
• DOI: 10.1039/c5fd00095e

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 p K a shift of +3.1 for A/AH + in the complex is mainly due to a lower deprotonation rate constant.