Significant van der Weals Effects in Transition Metal Complexes

There is, in general, very good experience using hybrid DFT to study mechanisms of enzyme reactions containing transition metals. For redox reactions, the B3LYP* functional, which has 15% exact exchange, has been shown to be particularly accurate. Still, there are some cases which have turned out to be quite difficult with large errors. In the present study, the effects of van der Waals interaction have been investigated for these cases, using the empirical formula of Grimme. The results are encouraging.