Mn–O–O Electron Spin Flip Mechanism Triggered by the Visible-Light Irradiation for the Generation of an Active Mn(V)–Oxo Complex from O2: Insight from Density Functional Calculations

Abstract

We reveal a new activation mechanism of O2 by electron spin flip for the formation of a high-valent Mn(V)–oxo corrolazine complex under O2 atmosphere and visible-light irradiation conditions. Ab initio calculations show that a loosely associated triplet complex from a quintet manganese corrolazine with a triplet O2 is formed initially in reaction. The subsequent strong bonding interactions between dioxygen with the manganese corrolazine, triggered by the visible-light irradiation, give rise to an increase in orbital splitting energy and drive the spin flip of electrons located at Mn and their rearrangement among the frontier orbitals, yielding the radical-like [Mn]–O–O species with high reactivity, which can easily abstract the hydrogen of the substrate to form the high-valent Mn(V)–oxo active oxidant through the following rebound reaction. Here the coupling interactions of dxz and dyz of Mn with the corresponding πxz23 and πyz23 orbitals of O2 may form two new extending π bonds, πxz34 and πyz34. Such an ...