Photochromism of the complex between 4'-(2-hydroxyethoxy)-7-hydroxyflavylium and beta-cyclodextrin, studied by H-1 NMR, UV-Vis, continuous irradiation and circular dichroism

• Type: Article in International Scientific Journal
• Date: 2014

Authors

Gago, S (Author) Other; Basilio, N (Author) Other; Fernandes, A (Author) Other; Victor de Freitas (Author) FCUP; Quintas, A (Author) Other; Pina, F (Author) Other

Journal

Title: Dyes and Pigments

Vol. 110

Pages: 106-112

ISSN: 0143-7208

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 11 Citations

Scopus - 11 Citations

Other information

Authenticus ID: P-009-QMV

DOI: 10.1016/j.dyepig.2014.04.038

Abstract (EN): 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 beta-cyclodextrin. The system was characterized by H-1 NMR, UV-Vis, continuous irradiation and circular dichroism. In the presence of beta-cyclodextrin 4.8 mM the pK(a)' is reduced to 2.2. The association constants with beta-cycloclextrin, follow the order trans-chalcone > quinoidal base > flavylium cation, respectively 1.7 x 10(3) M-1; 5.6 x 10(2) M-1; approximate to 0. The rate of inter-conversion of the network species increases in the presence of p-cyclodextrin circa 2.6 times. The appearance of an induced circular dichroism signal of trans-chalcone inside the beta-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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7