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Electrochemical CO2 and Proton Reduction by a Co(dithiacyclam) Complex

: Iffland, Linda; Siegmund, Daniel; Apfel, Ulf-Peter

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Zeitschrift für anorganische und allgemeine Chemie 646 (2020), No.13, pp.746-753
ISSN: 0044-2313
ISSN: 0372-7874
ISSN: 0863-1786
ISSN: 0863-1778
ISSN: 1521-3749
Journal Article, Electronic Publication
Fraunhofer UMSICHT Oberhausen ()
Dithiacyclam; cobalt; electrocatalysis; carbon dioxide; hydrogen

While [Ni(cyclam)]2+ and [Ni(dithiacyclam)]2+ complexes were shown to be potent electrocatalysts for the CO2 conversion, their respective Co complexes hitherto received only little attention. Herein, we report on the CoII complexes of the cyclam and dithiacyclam platform, describe their synthesis and reveal their rich solvent dependent coordination chemistry. We show that sulfur implementation into the cyclam moiety leads to a switch from a low spin CoII complex in [Co(cyclam)]2+ to a high spin form in [Co(dithiacyclam)]2+. Notably, while both complexes are capable to perform the reduction of CO2 to CO, H2 formation is generally preferred. Along this line, the complexes were shown to enable proton reduction from acetic acid. However, in comparison to [Co(cyclam)]2+, the altered electronics make [Co(dithiacyclam)]2+ complexes prone to deposit on the glassy carbon working electrode over time leading to an overall low faradaic efficiency for the reduction of protons or CO2.