Quantum Chemical Explorations of Redox Non-Innocence: Controlling and Interpreting Oxidation State in Physical Inorganic Chemistry

Redox non-innocent complexes display unique physical and chemical properties that are distinct from "redox innocent" complexes, and are important in numerous synthetic and biological systems. Our understanding of this behavior can be greatly benefitted by quantum chemistry, whether it is in the form of traditional ab initio calculations, or Density Functional Theory (DFT). Indeed, there are some features of redox non-innocence that can only be explored using theory, and this data provides a natural complement to experimental efforts in physical inorganic chemistry.;Here, several different interesting systems that display redox non-innocence and/or redox-active ligands have been studied computationally. The electronic structure of high-valent Mn(V) oxo systems, have been investigated using DFT and Complete Active Space Self-consistent Field theory (CASSCF). These studies provided a definitive quantification of the diradical character of this bond and how this is related to spin state, physical oxidation state, and reactivity towards O--O bond formation. For the Mn(V) oxo system, the frontier molecular orbitals still display significant metal character, in contrast to an additional study on biphenyl elimination from group IV metal complexes via redox-active iminosemiquinonate ligands. Here the redox-active ligands mediate the actual electron-transfer, but the "redox innocent" metal center was still important for tuning reactivity. These projects were focused on interpreting the electronic structure and reactivity of specific systems, but a third project was concentrated on how to control when a bipyridine ligand will become redox-active, and how frontier molecular orbital theory can and cannot be used to this end. A final project was on how a Bi(V) complex can promote thioglycoside anomerization. This complex did not exhibit any redox non-innocence in its most relevant chemistry, but we do predict that its phenyl ligands will become redox-active under electrochemical or single-electron transfer conditions.