MOLECULAR MECHANICAL CALCULATIONS OF THE MOLECULAR-STRUCTURE OF 8-COORDINATE EUROPIUM COMPLEXES

Molecular mechanics methods were applied to the determination of the s tructure of eight-coordinate europium complexes: tris(acetylacetonato) Eu(III) trihydrate, tris(acetylacetonato)(1,10-phenanthroline)Eu(III), and tetrakis(benzoylacetonato)Eu(III). Optimization of MM2 force-fiel d parameters and improvement of the calculation method were carried ou t using models of the complexes based on X-ray structural investigatio ns. Steric ligand-ligand interactions in the first coordination sphere were treated as dominant for the lanthanide complexes. The major cont ributions to the energy are those of nonbonded 1,3-interactions betwee n the atoms directly bound to the europium atom. The results of the ca lculations agree well with the crystal structures of the mentioned com plexes.