Synthesis and characterization of flavylium salts having three types color depending on recrystallization conditions

Three types of flavylium salts (FVs, yellow, green and red) have been synthesized and the colors depended on recrystallization conditions. The existence of these color states was confirmed by diffuse reflectance spectra. The spectra were almost the same as the absorption spectra in ethanol solution. The molecular state of FVs in crystals will be the same as that in solutions. The crystal colors of the FVs are controlled by the recrystallization conditions.