A series of substituted 2-hydroxychalcones (HC) were prepared, most of which underwent efficient and clean photochemical conversion into flavylium cations (FV) in acidic solution and polymer film, although strongly dependent on the pH and medium conditions as well as the HC structures. 4′-Methoxy and 4′-dimethylamino derivatives showed relatively high thermal stabilities of the colored mixtures, well-separated absorption bands of the HC and FV forms, almost quantitative conversion from HC to FV in the photostationary-state mixtures, and good photochromic performances in solution and polymer film, without suffering from the dissolved oxygen or moisture. A few of them showed relatively high reversibilities in the HC–FV interconversions under special pH and medium conditions.
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Matsushima et al. (1992) studied this question.
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