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

作者：Quattrociocchi Daniel Garcez S; Monsores Meuser Marcos Vinicius; Ferreira Glaucio Braga; Carneiro Jose Walkimar de M; Stoyanov Stanislav R; da Costa Leonardo Moreira

来源：Journal of Molecular Modeling, 2017, 23(2): 60.

DOI：10.1007/s00894-017-3240-0

• Ca2+ cation
• Chelate effect
• Inorganic scaling
• Bidentate carbonyl ligands
• Ionophore
• Density functional theory (DFT)
• Energy decomposition analysis

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 sp(2) 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 sub-stituent 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.

• 出版日期2017-2