Journal of Computational Chemistry, 2001, v. 22, N1, 38.

Molecular Mechanics Calculations of beta-Diketonate, Aqua, And Aqua-beta-Diketonate Complexes of Lanthanide Ions Using Gillespie-Kepert Model

Michael G. Razumov, Vladimir L. Melnikov and Igor V. Pletnev

Moscow State University, Moscow, 119899 Russia

Abstract - A version of molecular mechanics based on the Gillespie-Kepert model of coordination bonds "repulsion" is applied to lanthanide complexes. The force field parameters are developed which describe the structure of beta-diketonate-, aqua-, and mixed aqua-beta-diketonate complexes with good accuracy; the same parameters are applicable to various coordination numbers/polyhedra. For the aqua complexes, typical root-mean-square deviation (calculated vs. X-ray experimental values) is 0.02 A in Ln-O bond lengths and 2.0 deg. in O-Ln-O valence angles. For most of the other compounds, the same precision is achieved in coordination bond lengths, while 3.5 deg. is a typical precision for coordination bond angles. Calculations successfully reproduce the puckering of the beta-diketonate chelate rings, as well as the relative stability of isomers for a representative example.