Efficacy of Redox–Active Cu(II) Dipyrrin Complexes toward Electrochemical Reduction of CO₂

New D-A-type catalysts based on Cu (II) complexes (<b>C1</b> and <b>C2</b>) including dipyrrin ligands with phenothiazine/carbazole as the <i>meso</i>-substituent have been described. The complexes have been thoroughly characterized by various methods (¹H, ¹³C, ESI-MS, EPR, and UV-vis studies), and structures of both <b>C1</b> and <b>C2</b> unequivocally determined by X-ray single crystal analyses. The catalysts <b>C1</b> and <b>C2</b> are stable at room temperature and exhibit Faradaic efficiency values of ∼56% (<b>C1</b>) and ∼46% (<b>C2</b>) toward homogeneous reduction of CO₂ to CO. The release of CO has been validated by gas chromatographic (GC) studies. Electron-rich phenothiazine and carbazole included in the catalysts facilitate proton transfer, enabling rapid and selective formation of CO over H₂ with FE_H2 values of ∼22% for <b>C1</b> and ∼7% for <b>C2</b> and turnover numbers (TON) of ∼46 for <b>C1</b> and ∼21 for <b>C2</b>. Furthermore, the formation of formate ions has been affirmed by ion chromatography (<b>C1</b>, ∼16%; <b>C2</b>, ∼18%). Detailed electrochemical studies and product analyses suggested that <b>C1</b> displays superior catalytic activity relative to <b>C2</b> which has been further supported by theoretical studies.