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 (
ΦCO=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.
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