Mononuclear Iron Pyridinethiolate Complex Promoted CO Photoreduction via Rapid Intramolecular Electron Transfer.

Designing earth-abundant metal complexes as efficient molecular photocatalysts for visible light-driven CO reduction is a key challenge in artificial photosynthesis. Here, we demonstrated the first example of a mononuclear iron pyridine-thiolate complex that functions both as a photosensitizer and catalyst for CO reduction. This single-component bifunctional molecular photocatalyst efficiently reduced CO to formate and CO with a total turnover number (TON) of 46 and turnover frequency (TOF) of 11.5 h in 4 h under visible light irradiation. Notably, the quantum yield was determined to be 8.4 % for the generation of formate and CO at 400 nm. Quenching experiments indicate that high photocatalytic activity is mainly attributed to the rapid intramolecular quenching protocol. The mechanism investigation by DFT calculation and electrochemical studies revealed that the protonation of Febpy(pyS) is indispensable step for photocatalytic CO reduction.