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

Identifier

017770

Type of Spiritual Experience

Background

A description of the experience

J Phys Chem A. 2008 Dec 4;112(48):12475-84. doi: 10.1021/jp805463p.

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

Cornard JP1, Lapouge C, Dangleterre L, Allet-Bodelot C.

 

  • 1LASIR, CNRS UMR8516, Universite des Sciences et Technologies de Lille, Bat C5, 59 655 Villeneuve d'Ascq Cedex, France.

Abstract

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. In low acidic aqueous medium, the complexation of Pb(II) has been followed by electronic absorption spectrometry. The formation of two complexes of stoichiometry metal:ligand 1:1 (log beta(1:1) = 3.39) and 2:1 (log beta(2:1) = 7.12) has been highlighted with use of chemometric methods. The theoretical spectrum of the 1:1 complex obtained by TD-DFT methodology shows the formation of a chelate [Pb(H(2)CGA)(H(2)O)(3)](+) with the metal fixation at the level of the carboxylate function. The second complexing site, the catechol moiety, is rapidly involved in the formation of the 2:1 complex from molar ratios [metal]/[ligand] higher than 0.1. The electronic transitions calculated for both free ligand and complexes involved the same molecular orbitals, and no ligand-metal or metal-ligand charge transfer is observed.

PMID:  18991429

The source of the experience

PubMed

Concepts, symbols and science items

Concepts

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Science Items

Activities and commonsteps

Activities

Overloads

Lead poisoning

Suppressions

Chelation agents
Chlorogenic acid

Commonsteps

References