Solvent effect on Al(III) hydrolysis constants from density functional theory

Moira K. Ridley, Hans Lischka, Daniel Tunega, Adelia J.A. Aquino

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Density functional theory was used to compute proton affinity constants (pK a values) for the four step-wise hydrolysis reactions of the aluminum cation (Al 3+ through [Al(OH) 4 ] ). The hydrolysis species were modelled as (Formula presented.) complexes. Solvation effects were evaluated combining two approaches; initially, microsolvation of the Al-species was achieved by varying the number of explicit solvation water molecules surrounding the Al-complexes and reaction partner H 2 O/H 3 O + species. In the second approach, the long-range polar solvent effect (global solvation) was included by using the COSMO continuum solvation model in the DFT calculations. pK a values for the hydrolysis reactions were calculated using a thermodynamic cycle, and were calculated directly from the global solvation data. The computed energies, optimised coordination structures, bond lengths, charge from natural population analyses, ionic potential, and H-bonding for the Al-hydrolysis species varied depending on the solvation approach. Similarly, calculated pK a values varied for each solvation approach. Overall cumulative pK a values calculated directly from the global solvation showed good agreement with experimental data.

Original languageEnglish
Pages (from-to)1507-1518
Number of pages12
JournalMolecular Physics
Issue number9-12
StatePublished - Jun 18 2019


  • Aluminum hydrolysis
  • density functional theory
  • proton affinity constants
  • solvent effect


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