Complexation of lead(II) by chlorogenic acid: experimental and theoretical study.

Density functional theory (DFT) structure calculations and time-dependent DFT electronic excitation calculations have been performed on chlorogenic acid (H(3)CGA), a polyphenolic compound, used as a model molecule of humic substances. The different deprotonated forms of H(3)CGA have also been investigated. H(3)CGA is a multisite ligand that presents several metal complexing sites in competition, notably the carboxylic and catechol moieties.

Spectroscopic and theoretical studies of the Zn(II) chelation with hydroxyflavones.

The Zn(II) complexation of three naturally occurring organic compounds (3-hydroxyflavone, 5-hydroxyflavone, and 3',4'-dihydroxyflavone) has been investigated by electronic spectroscopy combined with quantum chemical calculations. These three ligands, which differ in the nature of their chelating site, lead to the formation of a complex of 1:1 stoichiometry. The experimental results show that it is possible to class the three studied sites, according to their chelating power toward Zn(II), in the following way: alpha-hydroxy-carbonyl > beta-hydroxy-carbonyl > catechol.