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

摘要

The interaction of Ianthanide(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)2CI2,Ln(cca)2(H2O)2-Cl,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-.