Evidence of Sulfur Non-Innocence in [CoII(dithiacyclam)]2+-Mediated Catalytic Oxygen Reduction Reactions |
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| Authors: | MSc Beatrice Battistella MSc Linda Iffland-Mühlhaus BSc Maximillian Schütze Dr Beatrice Cula Dr Uwe Kuhlmann Prof Dr Holger Dau Prof Dr Peter Hildebrandt Dr Thomas Lohmiller Dr Stefan Mebs Prof Dr Ulf-Peter Apfel Prof Dr Kallol Ray |
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| Institution: | 1. Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany;2. Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany;3. Institut für Chemie, Fakultät II, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany;4. Institut für Physik, Freie Universität zu Berlin, Arnimallee 14, 14195 Berlin, Germany |
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| Abstract: | In many metalloenzymes, sulfur-containing ligands participate in catalytic processes, mainly via the involvement in electron transfer reactions. In a biomimetic approach, we now demonstrate the implication of S-ligation in cobalt mediated oxygen reduction reactions (ORR). A comparative study between the catalytic ORR capabilities of the four-nitrogen bound Co(cyclam)]2+ ( 1 ; cyclam=1,5,8,11-tetraaza-cyclotetradecane) and the S-containing analog Co(S2N2-cyclam)]2+ ( 2 ; S2N2-cyclam=1,8-dithia-5,11-diaza-cyclotetradecane) reveals improved catalytic performance once the chalcogen is introduced in the Co coordination sphere. Trapping and characterization of the intermediates formed upon dioxygen activation at the CoII centers in 1 and 2 point to the involvement of sulfur in the O2 reduction process as the key for the improved catalytic ORR capabilities of 2 . |
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| Keywords: | Cobalt Macrocyclic Ligands O−O Activation Reactive Intermediates Spectroscopy |
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