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Issue 2, 2017
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Hiding and unveiling trans-chalcone in a constrained derivative of 4′,7-dihydroxyflavylium in water: a versatile photochromic system

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Abstract

A structurally constrained derivative of 4′,7-dihydroxyflavylium was studied in aqueous solution and in CTAB micelles by pH jumps, flash photolysis and continuous irradiation with spectroscopic details assessed as well by theoretical calculations. In water, up to pH = 8, the compound shows only acid base chemistry with deprotonation of the flavylium cation to form a quinoidal base that further deprotonates with pKas of 4.8 and 7.4. In the basic region, unprotonated trans-chalcones are formed. No neutral trans-chalcone (Ct) is formed in water preventing the establishment of the well-known photochromism involving photoisomerization of this species with subsequent formation of the flavylium cation. Addition of 0.02 M CTAB drastically changes the mole fraction distribution of species, leading to the formation of Ct (χCt = 1 at pH = 5) and unveiling a photochromic behavior with a pH-tunable colour contrast in a large pH range (2 < pH < 8). The Ct species can be hidden again (irreversibly) upon addition of α-cyclodextrin that disrupts the CTAB micelles, reverting the system to its initial mole fraction distribution of species. These supramolecular inputs work atop the molecular reaction networks by modifying their species’ mole fraction distribution.

Graphical abstract: Hiding and unveiling trans-chalcone in a constrained derivative of 4′,7-dihydroxyflavylium in water: a versatile photochromic system

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Publication details

The article was received on 27 Jul 2016, accepted on 30 Sep 2016 and first published on 10 Oct 2016


Article type: Paper
DOI: 10.1039/C6OB01607C
Citation: Org. Biomol. Chem., 2017,15, 338-347
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    Hiding and unveiling trans-chalcone in a constrained derivative of 4′,7-dihydroxyflavylium in water: a versatile photochromic system

    M. Pessêgo, S. Gago, N. Basílio, C. A. T. Laia, A. Jorge Parola, J. C. Lima and F. Pina, Org. Biomol. Chem., 2017, 15, 338
    DOI: 10.1039/C6OB01607C

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