Probing the Effects of Electron Deficient Aryl Substituents and a π-System Extended NHC Ring on the Photocatalytic CO₂ Reduction Reaction with Re-pyNHC-Aryl Complexes**

The ever-expanding need for renewable energy can be addressed in part by photocatalytic CO₂ reduction to give fuels via an artificial photosynthetic process driven by sunlight. A series of rhenium photocatalysts are evaluated in the photocatalytic CO₂ reduction reaction and via photophysical, electrochemical, and computational studies. The impact of various electron withdrawing substituents on the aryl group of the pyNHC-aryl ligand along with the impact of extending conjugation along the backbone of the ligand is analyzed. A strong correlation between excited-state lifetimes, photocatalytic rates, and computationally determined dissociation energy of the labile ligand of these complexes is observed. Additionally, computed orbital analysis provides an added understanding, which allows for prediction of the potential impact of an electron withdrawing substituent on photocatalysis.