Characterization and Thermodynamic Analysis of a Series of MnIII-OH Complexes that undergo Hydrogen Atom Transfer Reactions

Abstract

Abstract Mononuclear MnIII-hydroxo motifs employ hydrogen atom transfer (HAT) reactions in biology and synthetic systems to oxidize a wide range of CH or OH bonds. Extensive studies on high valent Fe and Mn model systems exist, while studies on low and mid valent manganese complexes are less explored. In an effort to broaden the knowledge on structure and reactivity relationships of MnIII-OH motifs in HAT reactivity, a novel MnIII-OH complex is introduced to the [MnIII(OH)(dpaqR)](OTf) series. Understanding the HAT reactivity of MnIIIOH moieties in biological reactions rely on their reaction driving forces that are governed by the redox potential of the oxidant and the pKa value of the proton abstractor. However determining these thermodynamic parameters for biological systems is difficult. Alternatively, an understanding about these parameters can be obtained by studying their corresponding synthetic model systems. In an effort to understand the HAT step of the Mn-lipoxygenase catalytic cycle, a series of [MnII(OH2)(dpaqR)]+ complexes were prepared.