New Photosensitizers Based on Heteroleptic CuI Complexes and CO2 Photocatalytic Reduction with [NiII(cyclam)]Cl2

Earth-abundant metal complexes have been at- tracting increasing attention in the field of photo(redox)ca- talysis. In this work, the synthesis and full characterisation of four new heteroleptic CuI complexes are reported, which can work as photosensitizers. The complexes bear a bulky diphosphine (DPEPhos = bis[(2-diphenylphosphino)phenyl] ether) and a diimine chelating ligand based on 1-benzyl-4- (quinol-2’yl)-1,2,3-triazole. Their absorption has a relative maximum in the visible-light region, up to 450 nm. Thus, their use in photocatalytic systems for the reduction of CO2 with blue light in combination with the known catalyst [NiII(cyclam)]Cl2 was tested. This system produced CO as the main product through visible light (l = 420 nm) with a TON up to 8 after 4 hours. This value is in line with other photo- catalytic systems using the same catalyst. Nevertheless, this system is entirely noble-metal free.