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Evidence of Sulfur Non‐Innocence in [CoII(dithiacyclam)]2+‐Mediated Catalytic Oxygen Reduction Reactions
Battistella, Beatrice; Iffland‐Mühlhaus, Linda; Schütze, Maximillian; Cula, Beatrice; Kuhlmann, Uwe; Dau, Holger; Hildebrandt, Peter; Lohmiller, Thomas; Mebs, Stefan; Apfel, Ulf‐Peter; Ray, Kallol
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.
