Sulphur vs NH Group: Effects on the CO2 Electroreduction Capability of Phenylenediamine-Cp Cobalt Complexes

The cobalt complex (I) with cyclopentadienyl and 2-aminothiophenolate ligands was investigated as a homogeneous catalyst for electrochemical CO2 reduction. By comparing its behavior with an analogous complex with the phenylenediamine (II), the effect of sulfur atom as a substituent has been evaluate...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2023-03, Vol.28 (5), p.2364
Main Authors: Melis, Nicola, Mocci, Francesca, Vacca, Annalisa, Pilia, Luca
Format: Article
Language:English
Subjects:
Carbon dioxide
Catalysts
Catalytic activity
Chemical reactions
CO2
Cobalt
cobalt complex
Cobalt compounds
condensed Fukui function
cyclic voltammetry
Efficiency
Electric rates
Electrochemistry
Fossil fuels
Investigations
Ligands
Oxidation
Phenylenediamine
reduction
Sulfur
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Summary:The cobalt complex (I) with cyclopentadienyl and 2-aminothiophenolate ligands was investigated as a homogeneous catalyst for electrochemical CO2 reduction. By comparing its behavior with an analogous complex with the phenylenediamine (II), the effect of sulfur atom as a substituent has been evaluated. As a result, a positive shift of the reduction potential and the reversibility of the corresponding redox process have been observed, also suggesting a higher stability of the compound with sulfur. Under anhydrous conditions, complex I showed a higher current enhancement in the presence of CO2 (9.41) in comparison with II (4.12). Moreover, the presence of only one -NH group in I explained the difference in the observed increases on the catalytic activity toward CO2 due to the presence of water, with current enhancements of 22.73 and 24.40 for I and II, respectively. DFT calculations confirmed the effect of sulfur on the lowering of the energy of the frontier orbitals of I, highlighted by electrochemical measurements. Furthermore, the condensed Fukui function f − values agreed very well with the current enhancement observed in the absence of water.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules28052364