Binding Sites of Deprotonated Citric Acid and Ethylenediaminetetraacetic Acid in the Chelation with Ba2+, Y3+, and Zr4+ and Their Electronic Properties: a Density Functional Theory Study

Density functional calculations were performed on the metal complexes formed during the synthesis of barium zirconate (BZY). This compound has been synthesized previously, but the molecular interactions present during the formation of the ligand-metal complexes are unknown. In this study, calculations were carried out to determine the preferred coordination sites for the metal complexes. The cations Ba2+, Y3+, and Zr4+ were modeled to interact with two deprotonated chelating agents (citric acid [CA] and ethylenediaminetetraacetic acid [EDTA]) at strategic positions. Density functional theory (DFT) at the B3LYP level of theory with basis set 6-31G* and Universal Gaussian Basis Set (UGBS) was used. The relevant geometries, binding energies, and charge distributions of the complexes are reported. It was found that both CA and EDTA can bind the metal cations investigated in this study. Metal cations prefer to form bonds at the electron-rich sites of the chelating agents. Of the three metal cations considered, Zr4+ was found to possess the strongest bonds to deprotonated CA and EDTA, followed by Y3+ and then Ba2+.