Issue 9, 2007

Efficient photochromism from the network of chemical reactions of 7,4′-dihydroxyflavylium in CTAB micelles

Abstract

Differently from water, efficient photochromism with a strong colour contrast has been observed for the multistate compound 7,4′-dihydroxyflavylium in the presence of cetyl trimethylammonium bromide (CTAB) micelles. Two states are responsible for the photochromism: trans-chalcone (inside the micelle) in the dark, and flavylium cation, AH+, (in bulk water) upon irradiation. The kinetics of the system was characterized by flash photolysis and pH jumps. Evidence that the photochemical process leading to AH+ occurs in the micelle was achieved. The best colour contrast is obtained at pH = 1.5, from a solution practically colourless in the dark, to an intense yellow upon irradiation (quantum yield 0.4). The system is completely reversible with a lifetime of 38 min at room temperature, and exhibits a reasonable stability. A kinetic model capable of fitting the data from thermal entrance of the compound into the micelle, its ejection to bulk water upon irradiation and quantum yields of the photochemical process is proposed.

Graphical abstract: Efficient photochromism from the network of chemical reactions of 7,4′-dihydroxyflavylium in CTAB micelles

Supplementary files

Article information

Article type
Paper
Submitted
17 May 2007
Accepted
26 Jul 2007
First published
06 Aug 2007

Photochem. Photobiol. Sci., 2007,6, 1003-1009

Efficient photochromism from the network of chemical reactions of 7,4′-dihydroxyflavylium in CTAB micelles

R. Gomes, A. J. Parola, C. A. T. Laia and F. Pina, Photochem. Photobiol. Sci., 2007, 6, 1003 DOI: 10.1039/B707461A

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