DFT studies of the interactions between the [Ca(H2O)5]2+ cation and monofunctional oxo, aza, sulfur and phosphorous ligands

• Published in: Computational and theoretical chemistry 2016-01, Vol.1075, p.104-110
• Main Authors: Quattrociocchi, Daniel Garcez S., Ferreira, Glaucio Braga, da Costa, Leonardo Moreira, Carneiro, José Walkimar de M.
• Format: Article
• Language: English
• Subjects: [Ca(H2O)5]2+ cation; Aza; Energy decomposition analysis; Interaction strength; Oxo; Phosphorous and sulfur ligands
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2015.11.012

DFT calculations were performed to determine the affinity of the [Ca(H2O)5]2+ aquacomplex for monofunctional oxo, aza, sulfur and phosphorus ligands through the calculation of the interaction enthalpy and correlation with geometric, electronic and other energetic parameters (EDA method) that are related with the binding strength. [Display omitted] •Model compounds have exothermic interaction enthalpy with the metal center.•Phosphoryl and carbonyl groups are the most efficient to capture the Ca2+ cation.•Interactions of ligands with the metal center are modulated by electronic effects.•Electrostatic is the main component to the ligand–metal interaction. Quantum chemical calculations using the B3LYP/6-311++G(d,p) method were performed to determine the affinity of the [Ca(H2O)5]2+ cation for several monofunctional ligands. Four sets of ligands were studied: with oxygen binding atom (phosphoryl, amide, carboxylic acid, ketone, aldehyde, ether, alcohol, enol), nitrogen (imine, thiocyanic acid, nitrile, amine and ammonia), sulfur (thiocarbonyl, thioether and thioalcohol) and phosphorous (phosphine) binding atom. Compounds that bind via a double bonded oxygen atom have the strongest metal–ligand interaction, followed by compounds binding via nitrogen, singly bonded oxygen atom, sulfur and phosphine. The ligand with the strongest interaction, phosphine oxide, has an ionic resonance form with a negative charge on the binding oxygen atom that highly contributes to the hybrid geometry, what favors the interaction. The Energy Decomposition Analysis (EDA) of the interaction energy between the [Ca(H2O)5]2+ cation and the ligand shows that the electrostatic term is the major component of the interaction and represents at least 43.66% of the total interaction energy. The covalent component represents at least 28.09% of the total interaction energy. Along the set of compounds studied, the electrostatic component varies more than twice the covalent term. The repulsive and the dispersion components are roughly constant in all complexes.