Thermochromic properties of flavylium salts in agar-gel matrix

Flavylium salts exhibited a reversible thermochromism in an agar-gel matrix . Thus, by the temperature change from -3 to 50 degrees C, the absorption b and around 600 nm of 7-diethylamino-4'-dimethylaminoflavylium perchlorate i ncreased by a factor of ca. 1.5, while the band around 520 nm substantially decreased. Upon repeated cycles of the color change no significant fatigue s were observed. The thermochromic behaviors were tentatively rationalized to the dye aggregation phenomenon enhanced by the sol-gel matrix.