Novel synthesis of 3,3′-dihydroxyflavone and apparent formation constants of flavonoid-Ga(III) Complexes

Abstract

Flavonoids are a wide variety of polyphenolic compounds. They have many biological properties. They also exhibit a metallic ion complexation capacity, which is important since it has been found that biological properties these ligands present can be enhanced when complexation occurs. In this work four flavonoid-Ga(III) complexes were studied: 2′,4′,3- trihydroxychalcone-Ga(III), 2′,3-dihydroxychalcone-Ga(III), 3,7,3′-trihydroxyflavone-Ga(III), and 3,3′-dihydroxyflavone-Ga(III). All ligands were synthesized by our working group, contributing a novel, cheaper, and more simple way to obtain 3,3′-dihydroxyflavone. The stoichiometry of the complexes was determined using the Yoe-Jones method. Both chalcone-Ga(III) complexes presented 1:1 L:M stoichiometry; meanwhile flavone-Ga(III) complexes presented 2:1 L:M stoichiometry. The pK values were determined by means of a spectrophotometric method. Values obtained were: 2′,4′,3-trihydroxychalcone-Ga(III), pK = 4.35 ± 0.38; 2′,3-dihydroxychalcone-Ga(III), pK = 3.40 ± 0.17; 3,7,3′-trihydroxyflavone-Ga(III), pK = 7.74 ± 0.19; and 3,3′-dihydroxyflavone-Ga(III), pK = 8.46 ± 0.27. © 2010 American Chemical Society.