Ancillary Ligand Effects on Heteroleptic Ir<sup>III</sup> Dye in Dye‐Sensitized Photocatalytic CO<sub>2</sub> Reduction: Photoaccumulation of Charges on Arylated Bipyridine Ligand and Its Control on Catalytic Performance
Ju Hyoung Jo, Sunghan Choi, Ha‐Yeon Cheong, Jae‐Yoon Shin, Chul Hoon Kim, Dae Won Cho, Ho‐Jin Son, Chyongjin Pac, Sang Ook Kang
Abstract
Abstract Herein, we report the synthesis, and photochemical and ‐physical properties, as well as the catalytic performance, of a series of heteroleptic Ir III photosensitizers (IrPSs), [Ir(C^N) 2 (N^N Aryl )] + , possessing ancillary ligands that are varied with aryl‐substituents on bipyridyl unit [C^N=(2‐pyridyl)benzo[ b ]thiophen‐3‐yl (btp); N^N Aryl =4,4′‐Y 2 ‐bpy (Y=−Ph or −PhSi(Ph) 3 ]. We found that the π ‐extension of bipyridyl ligand by aryl‐substitution put bipyridyl ligand in use as an electron relay unit that performed charge accumulation before delivering to the catalytic center, greatly improving the overall CO 2 ‐to‐CO conversion activities. In a typical run, the aryl‐substituted IrPS ( t Bu IrP‐Ph Si )‐sensitized homogeneous systems (IrPS+Re I catalyst) gave a turnover number of 1340 ( Φ CO =24.2 %) at the early stage of photolysis (<5 h). This study demonstrates that the π ‐character modulation on the ancillary bipyridyl ligand is critical for forthcoming catalytic performance.