QM/MM modeling of the structures and properties of the β-diketonate-based lanthanide complexes

The structure and properties of the lanthanum and lutetium beta-diketonates and mixed Ln(dik)(3) ligand complexes with o-phenantroline, Ln(dik)(3)Phen, are modeled by using the quantum mechanical/molecular mechanical (QM/MM) technique with the universal force fields (UFF) in the MM part. The set of parameters for UFF was adjusted to obtain the adequate modeling of the structures. The Ln-O and Ln(dik)(3)-Phen bond energies were estimated by using the single-point calculations with Becke's three-parameter functional with Perdew-Wang correlational functional density functional theory. It is shown that the Ln-O and Ln(dik)(3)-Phen bond energies are decreasing in the series from nonbulky beta-diketonate ligands to their branched analogs. The introduction of the fluorinated substituents leads to substantial increase in bond energy. The natural bond orbital analysis was used for characterization of electronic structure of the complexes. (c) 2005 Wiley Periodicals, Inc.