title: Ligand non-innocence and strong correlation in manganese superoxide dismutase mimics.
abstract: 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 1019variables, 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.
authors.affiliation: Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. damazz@uchicago.edu.
authors.forename: Alexandra R
authors.initials: AR
authors.lastname: McIsaac
authors.affiliation: Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, IL 60637, USA. damazz@uchicago.edu.
authors.forename: David A
authors.identifier: http://orcid.org/0000-0002-9938-3886
authors.initials: DA
authors.lastname: Mazziotti
mesh_terms: D032701:Biomimetics; D008024:Ligands; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*
chemical_list: D008024:Ligands; D011166:Porphyrins; D013482:Superoxide Dismutase