Find in Library

The cobalt complex (<b>I</b>) 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 (<b>II</b>), 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 <b>I</b> showed a higher current enhancement in the presence of CO₂ (9.41) in comparison with <b>II</b> (4.12). Moreover, the presence of only one -NH group in <b>I</b> 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 <b>I</b> and <b>II</b>, respectively. DFT calculations confirmed the effect of sulfur on the lowering of the energy of the frontier orbitals of <b>I</b>, highlighted by electrochemical measurements. Furthermore, the condensed Fukui function <b><i>f ⁻</i></b> values agreed very well with the current enhancement observed in the absence of water.