Molecular Mechanics Force Field for Modeling Technetium(V) Complexes

A molecular mechanics (MM) force field is reported for modeling square pyramidal complexes of the Tc-(V) oxo group, which, as the {sup 99m}Tc radioisotope, are important in diagnostic nuclear medicine. A novel aspect of the parametrization is the inclusion of significant barriers to rotation about the Tc-L bonds. These barriers to rotation are interpreted in terms of overlap between filled p {pi} orbitals on the donor atoms and oxygen and d orbitals on the Tc.