Reinvestigation of the mechanism of dioxygen activation at a MnII(cyclam) center

Tarali Devi; Stefan Mebs; Dibya Jyoti Barman; Amanda Opis-Basilio; Michael Haumann; Kallol Ray

doi:10.1016/j.jinorgbio.2024.112809

Reinvestigation of the mechanism of dioxygen activation at a Mn^II(cyclam) center

J Inorg Biochem. 2024 Dec 9:264:112809. doi: 10.1016/j.jinorgbio.2024.112809. Online ahead of print.

Authors

Tarali Devi¹, Stefan Mebs², Dibya Jyoti Barman³, Amanda Opis-Basilio³, Michael Haumann², Kallol Ray⁴

Affiliations

¹ Indian Institute of Technology Hyderabad, Telangana 502284, India; Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany. Electronic address: taralidevi@chy.iith.ac.in.
² Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
³ Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany.
⁴ Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany. Electronic address: kallol.ray@chemie.hu-berlin.de.

PMID: 39705751
DOI: 10.1016/j.jinorgbio.2024.112809

Abstract

This study deals with the unprecedented reactivity of a [(cyclam)Mn^II(OTf)₂] (3-cis; OTf = CF₃SO_3^-) with O₂, which, depending on the presence or absence of a hydrogen atom donor like 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H), selectively generates di-μ-oxo Mn(III)Mn(IV) (1) or Mn^IV₂ (2) complexes, respectively. Both dimers have been characterized by different techniques including single-crystal X-ray diffraction, X-ray absorption spectroscopy, and electron paramagnetic resonance. Oxygenation reactions carried out with labeled ¹⁸O₂ and Resonance Raman spectroscopy unambiguously show that the oxygen atoms present in the Mn^IVMn^III dimer originate from O₂. Experimental evidences are provided for a novel method of dioxygen activation involving three Mn ions or two Mn ions and TEMPO-H to generate the bis(μ-oxo)dimanganese(IV) or bis(μ-oxo) dimanganese(III, IV) cores, respectively.

Keywords: Bis(μ-oxo) manganese dimer; Density functional theory; High-valent manganese; Inverse kinetic isotope effect; Kinetic studies; O(2) activation.