Electronic structure calculation study of metal complexes with a phytosiderophore mugineic acid

Structural and thermodynamic properties of biologically important metal–mugineic acid complexes have been studied from the theoretical side in order to understand the metal-chelating mechanism of phytosiderophore mugineic acid at an atomic level. Density-functional theory methods combined with the polarizable continuum model (PCM) have been employed to obtain free energies of complex formation and redox potentials for metal–mugineic acid complexes in solution. It has been found that the free energies of complex formation calculated at the B3LYP/PCM level of theory are in moderate agreement with available experimental results. The inclusion of explicit water molecules interacting with the carboxylic groups in deprotonated mugineic acid through strong hydrogen-bonds is found to further improve the calculated free energies of complex formation.

Structural and thermodynamic properties of biologically important metal complexes with mugineic acid, one of phytosiderophores, have been studied from the theoretical side. Density functional theory methods combined with the polarizable continuum model have been used to obtain free energies of formation and redox potentials for metal–mugineic acid complexes in solution.Figure optionsDownload as PowerPoint slideResearch highlights
► The B3LYP/TZVP level with the IEF-PCM continuum solvation model gives reliable results.
► The inclusion of explicit water molecules interacting with mugineic acid is essential.
► Ionic radius and electronic structure of the central metal affect the coordination structure.
► FeIII complex has an octahedral six-coordinate structure, while FeII center is five coordinate.
► Iron release mechanism involving the reduction of FeIII complex is understood from those results.