Computational Characterization of Ac^III-DOTA Complexes in Aqueous Solution

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• 1,4,7,10-tetrazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) is a common chelating agent.
• Actinium(III) complexes are of interest due to their potential applications.

Purpose of the Study:

• To investigate the thermodynamic stability of aqueous actinium(III)-DOTA complexes with various axial ligands.
• To understand the electronic structure and bonding characteristics influencing complex stability.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Relative Gibbs free energies were computed for different complexes.
• Electronic structure analyses were performed to determine bonding nature.

Main Results:

• Complexes with hydroxide (OH-) and fluoride (F-) as axial ligands are predicted to be more thermodynamically favorable.
• The [Ac(DOTA)(OH)]2- and [Ac(DOTA)(F)]2- complexes exhibit enhanced stability compared to those with H2O or DMSO.
• Covalent bonding between Ac(III) and OH-/F- is identified as the primary factor for increased stability.

Conclusions:

• The choice of axial ligand significantly impacts the stability of Ac(III)-DOTA complexes.
• Strong covalent interactions with hydroxide and fluoride lead to more stable actinium complexes.
• DFT provides valuable insights into the factors governing the thermodynamic stability of metal complexes.