The thermodynamic stability of hydrogen bonded and cation bridged complexes of humic acid models-A theoretical study

Adelia J.A. Aquino, Daniel Tunega, Hasan Pašalić, Georg Haberhauer, Martin H. Gerzabek, Hans Lischka

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Hydrogen bonded and cation bridged complexation of poly(acrylic acid) oligomers, representing a model compound for humic acids, with acetic acid and the herbicide (4-chloro-2-methylphenoxy) acetic acid (MCPA) have been studied by means of density functional theory. Solvation effects were computed by means of a combination of microsolvation (explicit insertion of water molecules) and global solvation (polarizable continuum approach). The stability of hydrogen bonded complexes in solution is characterized by a strong competition between solute and solvent molecules. The cation bridged complexes of the negatively charged (deprotonated) ligands were found to be strongly favored explaining the capability of humic acids to fixate anionic species from soil solutions and the ability to form cross-linking structures within the humic acid macromolecules.

Original languageEnglish
Pages (from-to)69-76
Number of pages8
JournalChemical Physics
Issue number1-3
StatePublished - Jun 16 2008



  • (4-Chloro-2-methylphenoxy) acetic acid
  • Acrylic acid
  • Adsorption
  • Calcium bridge
  • Density functional theory
  • Herbicides
  • Humic substances
  • MCPA

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