Use of the MM2 force field to model palladium complexes with nitrogen-containing aromatic ligands

Abstract Metal complexes form an important class of potential antiviral agents, but are less amenable to modelling studies than their organic counterparts. Molecular mechanics calculations on a series of palladium and palladium chloride complexes with the ligands 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, 2-amino-4-methylpyridine and benzonitrile have been performed using zero partial charges, partial charges with the in vacuo dielectric constant and partial charges with the dielectric constant of water. The resulting geometries exhibit more marked differences in the relative orientation of the ligand rings than in the coordination sphere. Semiempirical molecular orbital calculations on the free ligands confirm the experimentally observed mode of coordination when the MNDO or PM3 hamiltonians are used, but not with AM1.