EPR monitoring of in-situ Catalytic Oxidative Assembly of MnIII-MnIV Dimers via Monomeric MnIV=O

Abstract The oxidative evolution of Mn-catalysts via transient high-oxidation state, MnIII or MnIV, intermediates is often assumed in literature, however a direct in-situ evidence for cycling between high-oxidation states of Mn is scarce. Moreover, the involvement of dimeric [MnIV-MnIII] transients, has been invoked as active catalytic intermediate. Herein, we present a study by Dual-Mode EPR and Low-Temperature UV–Vis spectroscopies, on the monitoring of cycling of MnII, MnIII, MnIV states formed by a MnL catalytic system. It is found that, while starting as monomeric, the MnL catalyst, is capable to form in-situ stable oxo-bridged [Mn-Mn] dimers which are catalytically/redox-active.