No abstract

Chalcones present biological activity and are, therefore, currently studied for their therapeutic potential. They have shown antitumor, anti-inflammatory, antifungal and antibacterial properties. These compounds occur in nature as secondary metabolites of plants and are precursors of flavonoid biosynthesis. Generally, they are not luminescent, but derivatives with some particular patterns of substitution can present fair quantum yields. Excited State Intramolecular Proton Transfer (ESIPT) is a particular case of tautomerization, and some molecules can exhibit ESIPT fluorescence if their structures incorporate an intramolecular hydrogen bonding interaction between a hydrogen donor (-OH or -NH) and a hydrogen acceptor. If the dye is fluorescent, emission from both tautomers may be observed, leading to a dual emission. The chalcones with a strong push–pull character, compounds 2c, 3c and 4c, presented dual emission of keto–enol tautomerism as a consequence of ESIPT.