A density functional theory investigation of the interaction of the tetraaqua calcium cation with bidentate carbonyl ligands

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• 作者：Daniel Garcez S. Quattrociocchi…
• 关键词：Ca2+ cation ; Chelate effect ; Inorganic scaling ; Bidentate carbonyl ligands ; Ionophore ; Density functional theory (DFT) ; Energy decomposition analysis
• 刊名：Journal of Molecular Modeling
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：23
• 期：2
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Computer Applications in Chemistry; Molecular Medicine; Computer Appl. in Life Sciences; Characterization and Evaluation of Materials; Theoretical and Computational Chemistry;
• 出版者：Springer Berlin Heidelberg
• ISSN：0948-5023
• 卷排序：23

文摘

Calcium complexes with bidentate carbonyl ligands are important in biological systems, medicine and industry, where the concentration of Ca2+ is controlled using chelating ligands. The exchange of two water molecules of [Ca(H₂O)₆]2+ for one bidentate monosubstituted and homo disubstituted dicarbonyl ligand was investigated using the B3LYP/6-311++G(d,p) method. The ligand substituents NH₂, OCH₃, OH, CH₃, H, F, Cl, CN and NO₂ are functional groups with distinct electron-donating and -withdrawing effects that bond directly to the sp2 C atom of the carbonyl group. The geometry, charge and energy characteristics of the complexes were analyzed to help understand the effects of substituents, spacer length and chelation. Coordination strength was quantified in terms of the enthalpy and free energy of the exchange reaction. The most negative enthalpies were calculated for the coordination of bidentate ligands containing three to five methylene group spacers between carbonyls. The chelate effect contribution was analyzed based on the thermochemistry. The electronic character of the substituent modulates the strength of binding to the metal cation, as ligands containing electron-donor substituents coordinate stronger than those with electron-acceptor substituents. This is reflected in the geometric (bond length and chelating angle), electronic (atomic charges) and energetic (components of the total interacting energy) characteristics of the complexes. Energy decomposition analysis (EDA)—an approach for partitioning of the energy into its chemical origins—shows that the electrostatic component of the coordination is predominant, and yields relevant contribution of the covalent term, especially for the electron-withdrawing substituted ligands. The chelate effect of the bidentate ligands was noticeable when compared with substitution by two monodentate ligands.