Understanding the Catalase-Like Activity of a Bioinspired Manganese(II) Complex with a Pentadentate NSNSN Ligand Framework. A Computational Insight into the Mechanism

Abstract

The mechanism of H2O2 dismutation catalyzed by the recently reported 2,6-bis[((2-pyridylmethyl)thio)methyl]pyridine-Mn(II) complex ([MnS2Py3(OTf)2]) has been investigated by density functional theory using the S12g functional. The complex has been analyzed in terms of its coordination properties and the reaction of [MnS2Py3]2+ in a distorted square pyramidal coordination geometry with two hydrogen peroxide molecules has been investigated in our calculations. The sextet, quartet, and doublet potential energy profiles of the catalytic reaction have been explored. In the first dismutation process, the rate-determining step (RDS) is found to be the asymmetric O–O bond cleavage, which occurs on the sextet potential energy profile. A subsequent spin crossover from sextet to quartet, associated with a coordination rearrangement around the metal, can take place to generate a stable Mn(IV) dihydroxo intermediate. This could disfavor the ping-pong mechanism commonly considered to describe the H2O2 dismutation react...