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Ligand non-innocence and strong correlation in manganese superoxide dismutase mimics.

Alexandra R McIsaacDavid A Mazziotti
Published in: Physical chemistry chemical physics : PCCP (2018)
We examine the 1-electron reduction of manganese porphyrin complexes Mn(iii) porphyrin and Mn(iii) TDE-2-ImP5+, which have attracted recent interest due to their properties as superoxide dismutase mimics. We perform a series of electronic structure calculations using the variational 2-electron reduced density matrix (2-RDM) method with a large [30,30] active space that represents a wavefunction with 1019 variables, as well as the more traditional complete active space self-consistent field (CASSCF) method with a [14,14] active space. We show that the larger 2-RDM calculation, intractable with CASSCF, is required to capture the full effects of electron correlation in the molecule and predict the non-innocence of the porphyrin ligand during the reduction. The CASSCF method predicts single-reference systems exhibiting a metal-centered reduction, but the 2-RDM method predicts a strongly correlated system exhibiting a ligand-centered reduction. Based on these results, we find that the porphyrin ligand is reduced rather than the manganese, and suggest that the electron correlation plays a role in driving the ligand non-innocence.
Keyphrases
  • electron transfer
  • photodynamic therapy
  • metal organic framework
  • hydrogen peroxide
  • energy transfer
  • room temperature
  • density functional theory
  • monte carlo
  • ionic liquid