Calculating the excited state reactivity of a manganese(IV)-oxo species with a negatively charged ligand

It was previously found that Mn^IVO species with neutral ligands perform C-H activation reactions through an “excited state reactivity” (ESR), where a valence electron in the Mn^IVO moiety is spontaneously excited to a higher orbital to create a more potent reactant. We extend this to a Mn^IVO compound with a negatively charged ligand ([Mn^IV(O)(DPAQ)]⁺), which we investigate with density functional theory. It is found that ESR are indeed preferable even in this case, and that the ligand charge may only have an indirect effect on ESR. Instead, ligand rigidity is proposed to affect the ESR rate more directly. In addition, an example of a new β-electron transfer pathway was found, where three key orbitals mix to deliver the incoming electron to its final orbital position. This study supports the notion that ESR may be more common in C–H activation reactions of Mn^IVO compounds than what is so far known.