Unexpected wavelength dependency of the photocatalytic CO₂ reduction performance of the well-known (bpy)Re(CO)₃Cl complex

Abstract

The selective photocatalytic reduction of CO₂ to CO has often been accomplished using complexes incorporating the Re(CO)₃Cl fragment. We now discovered that the photocatalytic performance of the well-known parent compound (bpy)Re(CO)₃Cl (bpy = 2,2'-bipyridine) surprisingly depends on the illumination wavelengths: the turnover numbers (TONs) measured using various cut-off filters showed an increased photocatalytic activity when irradiated with visible light with wavelengths longer than 450 nm - even if the compound hardly absorbs light in this wavelength region. Therefore, catalytic, spectroscopic and theoretical investigations were performed to explain this exceptional effect.