title: Interaction between alkaline earth cations and oxo ligands: a DFT study of the affinity of Mg2+ for carbonyl ligands.
abstract: The affinities of Mg(2+) for various substituted carbonyl ligands were determined at the DFT (B3LYP/6-31+G(d)) and semi-empirical (PM6) levels of theory. Two sets of carbonyl ligands were studied: monosubstituted [aldehydes R-CHO and RPh-CHO] and homodisubstituted [ketones R(2)C=O and (RPh)(2)C=O], where R = NH(2), OCH(3), OH, CH(3), H, F, Cl, Br, CN, or NO(2)). In the (RPh)(2)CO case, the R group was bonded to the para position of a phenyl ring. The enthalpies of interaction between the ligands and a pentaaquomagnesium(II) complex were calculated to determine the affinity of each ligand for the Mg(2+) cation and to correlate with geometrical and electronic parameters. These parameters exhibited the same trends for all of the ligands studied, showing that the affinity of Mg(2+) for electron-donating ligands is higher than its affinity for electron-withdrawing ligands. In the complexes, electron-donating groups increase both the electrostatic and the covalent components of the Mg-ligand interaction. This behavior correlates with the Mg-O(carbonyl) distance and the ligand electron-donor strength.
authors.affiliation: Programa de Pós-Graduação em Química, Universidade Federal Fluminense, Niteroi, Brazil.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Moreira da Costa
authors.forename: Stanislav R
authors.initials: SR
authors.lastname: Stoyanov
authors.forename: José
authors.initials: J
authors.lastname: Walkimar de M Carneiro
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D002412:Cations; D004583:Electrons; D007659:Ketones / Q000737:chemistry*; D008024:Ligands; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory
chemical_list: D000447:Aldehydes; D002412:Cations; D007659:Ketones; D008024:Ligands; D008274:Magnesium