New Photosensitizers Based on Heteroleptic Cu${}^I$ Complexes and CO${}_2$ Photocatalytic Reduction with [Ni${}^{II}$(cyclam)]Cl${}_2$

Earth‐abundant metal complexes have been attracting increasing attention in the field of photo(redox)catalysis. In this work, the synthesis and full characterisation of four new heteroleptic Cu${}^I$ 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 CO${}_2$ with blue light in combination with the known catalyst [Ni${}^{II}$(cyclam)]Cl${}_2$ was tested. This system produced CO as the main product through visible light (λ =420 nm) with a TON up to 8 after 4 hours. This value is in line with other photocatalytic systems using the same catalyst. Nevertheless, this system is entirely noble‐metal free.