Formation of a leuco Spirolactone from 4‐(2‐Carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium: Design of a Phase‐Change Thermochromic System Based on a Flavylium Dye |
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| Authors: | Raquel Gavara Dr César A T Laia Dr A Jorge Parola Dr Fernando Pina Prof |
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| Institution: | REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829‐516 Caparica (Portugal), Fax: (+35)?1212948550 |
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| Abstract: | A phase‐change thermochromic system was designed through the reversible transformation of the 4‐substituted flavylium dye 4‐(2‐carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium into its leuco form, in the presence of a developer (ethyldiisopropylamine) and a suitable solvent (e.g., acetonitrile, n‐pentadecanonitrile). The leuco form of the flavylium‐based dye is a spirolactone species whose ring opens at low temperature (below the solvent melting point) to form the blue flavylium cation. Decarboxylation of the lactone to give 4‐phenyl‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium was observed upon irradiation of the system with UV light, erasing the thermochromic effect. |
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| Keywords: | flavylium lactone photodecarboxylation spiro compounds thermochromism |
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