title: Theoretical study of metal-ligand interaction in Sm(III), Eu(III), and Tb(III) complexes of coumarin-3-carboxylic acid in the gas phase and solution.
abstract: The interaction of lanthanide(III) cations (Ln(III) = Sm(III), Eu(III), and Tb(III)) with the deprotonated form of the coumarin-3-carboxylic acid (cca-) has been investigated by density functional theory (DFT/B3LYP) and confirmed by reference MP2 and CCSD(T) computations. Solvent effects on the geometries and stabilities of the Ln(III) complexes were computed using a combination of water clusters and a continuum solvation model. The following two series of systems were considered: (i) Ln(cca)2+, Ln(cca)2+, Ln(cca)3 and (ii) Ln(cca)(H2O)2Cl2, Ln(cca)2(H2O)2Cl, Ln(cca)3. The strength and character of the Ln(III)-cca- bidentate bonding were characterized by calculated Ln-O bond lengths, binding energies, ligand deformation energies, energy partitioning analysis, sigma-donation contributions, and natural population analyses. The energy decomposition calculations predicted predominant electrostatic interaction terms to the Ln-cca bonding (ionic character) and showed variations of the orbital interaction term (covalent contributions) for the Ln-cca complexes studied. Electron distribution analysis suggested that the covalent contribution comes mainly from the interaction with the carboxylate moiety of cca-.
authors.affiliation: Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Ivelina
authors.initials: I
authors.lastname: Georgieva
authors.forename: Natasha
authors.initials: N
authors.lastname: Trendafilova
authors.forename: Adélia J A
authors.initials: AJ
authors.lastname: Aquino
authors.forename: Hans
authors.initials: H
authors.lastname: Lischka
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D012493:Samarium / Q000737:chemistry*; D012996:Solutions; D013725:Terbium / Q000737:chemistry*
chemical_list: D003374:Coumarins; D005740:Gases; D008024:Ligands; D012996:Solutions; D013725:Terbium; D012493:Samarium; D005063:Europium; C104227:coumarin-3-carboxylic acid