Spectroscopic and Thermodynamic Study of Chrysin and Quercetin Complexes with Cu(II)

Chrysin and quercetin are natural polyphenolic compounds which present benefits in human health because of their biological properties. These flavonoids also have the capacity to complex a wide variety of metallic ions which could affect their bioactivity. In order to assay the complexant capacity of flavonoids, the metallic ion Cu(II) was selected. The formation of two flavonoid–Cu(II) complexes in ethanolic solutions were studied, and both complexes presented 2:1 L–M stoichiometries. The apparent formation constants for quercetin–Cu(II) are higher than those of chrysin–Cu(II) ones, suggesting that quercetin may act as a better analytical reagent than chrysin. A molecular modeling analysis was performed in order to gain insight into the spectroscopic properties of the complexes.