Geometric and electronic structure of a peroxomanganese(iii) complex supported by a scorpionate ligand

Academic Article

Abstract

  • A monomeric MnII complex has been prepared with the facially-coordinating TpPh2 ligand, (TpPh2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate). The X-ray crystal structure shows three coordinating solvent molecules resulting in a six-coordinate complex with Mn-ligand bond lengths that are consistent with a high-spin MnII ion. Treatment of this MnII complex with excess KO2 at room temperature resulted in the formation of a MnIII-O2 complex that is stable for several days at ambient conditions, allowing for the determination of the X-ray crystal structure of this intermediate. The electronic structure of this peroxomanganese(iii) adduct was examined by using electronic absorption, electron paramagnetic resonance (EPR), lowerature magnetic circular dichroism (MCD), and variableerature variable-field (VTVH) MCD spectroscopies. Density functional theory (DFT), time-dependent (TD)-DFT, and multireference ab initio CASSCF/NEVPT2 calculations were used to assign the electronic transitions and further investigate the electronic structure of the peroxomanganese(iii) species. The lowest ligand-field transition in the electronic absorption spectrum of the MnIII-O2 complex exhibits a blue shift in energy compared to other previously characterized peroxomanganese(iii) complexes that results from a large axial bond elongation, reducing the metal-ligand covalency and stabilizing the σ-antibonding Mn dz2 MO that is the donor MO for this transition.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Colmer HE; Geiger RA; Leto DF; Wijeratne GB; Day VW; Jackson TA
  • Start Page

  • 17949
  • End Page

  • 17963
  • Volume

  • 43
  • Issue

  • 48