Interaction of lead (II) chloride with hydroxyflavones in methanol: A spectroscopic study

Model compounds, of reasonable size, which have chelating chemical functions (carboxylic, catechol, hydroxy-carbonyl) analogues with those met in the biopolymer of the organic matter of the soils, were studied so as to better understand the complexation processes of metal ions. The present paper reports on spectroscopic investigation of the complex formation of lead (II) with some hydroxyflavones. The purpose of this study is to determine the stoichiometric composition and stability constants of the complexes formed between Pb(II) and 3-hydroxyflavone, 5-hydroxyflavone and 3 ',4 '-dihydroxyflavone, respectively, in order to propose a classification of potential sites according to their chelating capacity. The combined use of electronic absorption spectroscopy and chemometrics methods allows reaching this objective. We have shown, that in methanol solution, the catechol function presents the greatest affinity for Pb(II) and leads to complex formation of higher stoichiometry than the other sites. The comparison of the results obtained for the complexation of Pb(II) and Al(III) shows a very different behaviour of the studied sites with respect to these two metals. (c) 2005 Elsevier Ltd. All rights reserved.