Abstract
The network of chemical reactions of the compound 4′-(2- hydroxyethoxy)-7-hydroxyflavylium and its photochromic properties were studied in the absence and presence of β-cyclodextrin. The system was characterized by 1H NMR, UV-Vis, continuous irradiation and circular dichroism. In the presence of β-cyclodextrin 4.8 mM the pK′a is reduced to 2.2. The association constants with β-cyclodextrin, follow the order trans-chalcone > quinoidal base > flavylium cation, respectively 1.7 × 103 M-1; 5.6 × 102 M -1; ≈0. The rate of inter-conversion of the network species increases in the presence of β-cyclodextrin circa 2.6 times. The appearance of an induced circular dichroism signal of trans-chalcone inside the β-cyclodextrin is described for the first time. It gives information about the position of the guest inside the host and allows the calculation of the respective association constant.
Original language | English |
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Pages (from-to) | 106-112 |
Number of pages | 7 |
Journal | Dyes and Pigments |
Volume | 110 |
Issue number | SI |
DOIs | |
Publication status | Published - 2014 |
Keywords
- Anthocyanins
- Cyclodextrin
- Flavylium
- Induced circular dichroism
- Kinetics
- Photochromism