*
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.