Photo-induced coloration of 2-hydroxychalcone in the clay interlayer

2-Hydroxychalcones are known to be converted to the colored flavylium form under UV irradiation. In this study, the photochemical conversion of two 2-hydroxychalcone derivatives (4′-dimethylamino-2-hydroxychalcone and 4′-methoxy-2-hydroxychalcone) has been carried out in the solid matrix by the intercalation into the layer of the clay, montmorillonite. The 2-hydroxychalcone has been adsorbed on the clay by modifying the clay interlayer with a cationic surfactant, dodecyltrimethylammonium chloride. The addition of an acidic compound (benzenesulfonic acid) has induced the successful coloring reaction of the 2-hydroxychalcone derivatives by the conversion to the flavylium under UV irradiation between the clay interlayer. A delayed coloration has been observed on the short time irradiation of 4′-methoxy-2-hydroxychalcone included in the clay layer.