Complexation of Cu(II) with synthetic polyphenol 3,3′-dihydroxyflavone: spectroscopic and thermodynamic study

Abstract

Flavones are polyphenolic compounds with many biological properties. They also exhibit a metallic ion complexation capacity, which can further enhance these properties. The synthetic polyphenol3,30-dihydroxyflavone was selected to study its ability to complex Cu(II), a metal ion of interest in biological media and industry. The complex stoichiometry and apparent formation constantin methanolic medium were evaluated using spectrophotometric techniques. The complex exhibited a 2:1 L:M stoichiometry and the stability constant at 25 °C was 1.18x10^10. Stability constantwas also determined at 15, 25, 30 and 35 °C in order to determine enthalpic, entropic and free Gibbs energy changes. These thermodynamic parameters indicate that formation reaction is exothermic and driving force is entropic. Data obtained is useful not only to characterize the complex but also to consider the flavone as a new analytical reagent.