Figure 24.

Six-coordinate [i.e., with an axially ligated base (B)] heme–Fe adducts bearing different reduced derivatives of dioxygen as axial ligands (i.e., superoxo, peroxo, and oxo). Inspired by the relevance of these adducts in various enzymatic systems (see section 2.1), small molecule models have been generated and interrogated in great detail. Significant insights gained from such models are discussed in the sections that follow, highlighting their applicability toward a more thorough understanding of the CcO enzymatic system.