Kinetics and mechanism of the reaction between chromium(III) and 3,4-dihydroxy-phenyl-propenoic acid (caffeic acid) in weak acidic aqueous solutions

Athinoula L. Petrou, Vladimiros Thoma, Konstantinos Tampouris

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Our study of the complexation of 3,4-dihydroxy-phenyl-propenoic acid by chromium(III) could give information on the way that this metal ion is available to plants. The reaction between chromium(III) and 3,4-dihydroxy-phenyl- propenoic acid in weak acidic aqueous solutions has been shown to take place by at least three stages. The first stage corresponds to substitution (I d mechanism) of water molecule from the Cr (H 2 O) 5 OH 2+ coordination sphere by a ligand molecule. A very rapid protonation equilibrium, which follows, favors the aqua species. The second and the third stages are chromium(III) and ligand concentration independent and are attributed to isomerisation and chelation processes. The corresponding activation parameters are Δ H 2(obs) = 28.6 ± 2.9kJ mol - 1, Δ S 2(obs) = -220± 10J K - 1 mol - 1, Δ H 3(obs) = 62.9 ± 6.7kJ mol - 1 and Δ S 3(obs) = -121± 22J K - 1 mol - 1. The kinetic results suggest associative mechanisms for the two steps. The associatively activated substitution processes are accompanied by proton release causing pH decrease.

Original languageEnglish
Article number624583
JournalBioinorganic Chemistry and Applications
Volume2008
DOIs
Publication statusPublished - 2008

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Inorganic Chemistry

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