Battistella, B.; Iffland-Mühlhaus, L.; Schütze, M.; Cula, B.; Kuhlmann, U.; Dau, H.; Hildebrandt, P.; Lohmiller, T.; Mebs, S.; Apfel, U.P.; Ray, K.: Evidence of Sulfur Non-Innocence in [Co-II(dithiacyclam)]2+-Mediated Catalytic Oxygen Reduction Reactions. Angewandte Chemie - International Edition 62 (2023), p. e20221407/1-7
10.1002/anie.202214074
Open Accesn Version
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.