Use of semi-empirical MO methods to describe transition metal systems.

The electronic structure of mol. systems contg. transition metal atoms is traditionally studied using methods based on d. functional theory. Although such an approach has been quite successful, the treatment of large systems,be they transition metal complexes, bioinorg. mols. or the solid state, is still extremely computationally demanding at this level, and may not be practical for many systems of interest. In addn. there is the ever present problem as to which functional is the most appropriate.We here discuss strategies in which semi-empirical MO methods are incorporated into electronic structure calcns. of metalloenzymes. We focus on the use of the most appropriate parameters,and the use of hybrid and other multilevel schemes that include semiempirical methods. Application to metalloenzymes involving copper, iron and molybdenum will be discussed. [on SciFinder (R)]