Document Type
Article
Publication Date
9-20-2023
Abstract
The abundance of manganese in nature and versatility to access different oxidation states have made manganese complexes attractive as catalysts for oxidation reactions in both biology and industry. Macrocyclic ligands offer the advantage of substantially controlling the reactivity of the manganese center through electronic tuning and steric constraint. Inspired by the manganese catalase enzyme, a biological catalyst for the disproportionation of H2O2 into water and O2, the work herein employs 12-membered tetra-aza macrocyclic ligands to study how the inclusion of and substitution to the pyridine ring on the macrocyclic ligand scaffold impacts the reactivity of the manganese complex as a H2O2 disproportionation catalyst. Synthesis and isolation of the manganese complexes was validated by characterization using UV–vis spectroscopy, SC-XRD, and cyclic voltammetry. Potentiometric titrations were used to study the ligand basicity as well as the thermodynamic equilibrium with Mn(II). Manganese complexes were also produced in situ and characterized using electrochemistry for comparison to the isolated species. Results from these studies and H2O2 reactivity showed a remarkable difference among the ligands studied, revealing instead a distinction in the reactivity regarding the number of pyridine rings within the scaffold. Moreover, electron-donating groups on the 4-position of the pyridine ring enhanced the reactivity of the manganese center for H2O2 disproportionation, demonstrating a handle for control of oxidation reactions using the pyridinophane macrocycle.
Recommended Citation
Freire, D. M.; Johnston, H. M.; Smith, K. J.; Pota, K.; Mekhail, M. A.; Kharel, S.; Green, K. N. Hydrogen Peroxide Disproportionation Activity Is Sensitive to Pyridine Substitutions on Manganese Catalysts Derived from 12-Membered Tetra-Aza Macrocyclic Ligands. Inorganic Chemistry 2023, 62 (39), 15842-15855. https://doi.org/10.1021/acs.inorgchem.3c01234
Copyright
American Chemical Society
Comments
This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Inorganic Chemistry, volume 62, issue 39, in 2023 following peer review. This article may not exactly replicate the final published version. The definitive publisher-authenticated version is available online at https://doi.org/10.1021/acs.inorgchem.3c01234.