Homo-and heteroleptic copper (I) complexes with nitrogen and phosphorus-based bidentate ligands have demonstrated efficiency not only as photosensitizers, but also as catalysts for inner sphere bond formation and SET. However, utilization of copper catalysts as photosensitizers for energy transfer mechanisms (EnT) has been relatively uncommon. In 2020, Poisson and co-workers reported a visible-light-induced E → Z isomerization of polarized alkenes using a Cu(OAc)₂/BINAP catalyst, facilitated by an oxazolidinone template that provides additional coordination (Figure ). Employing oxazolidinone as a template on the substrate for better coordination of copper (II) on the carbonyl oxygens,  -* gap in the substrate could be diminished, thereby inducing a bathochromic shift in absorption of the coordinated substrate. The wide range of explored alkenes underwent the isomerization in excellent yields and moderate to good diastereoselectivities (Figure ). Intriguingly, triplet quenchers such as oxygen and 1,3-cyclohexadiene (CHD) had no effect on the isomerization, while the presence of azulene (singlet and triplet quencher) strongly impeded the reaction (Figure ), suggesting a singlet state mechanism, elucidated in Figure . Substrate bound copper complex 23.8 undergoes energy transfer to provide singlet 1,2 diradical 23.9. Subsequent bond rotation yields the desired Z product (23.2). In 2021, Collins and co-workers expanded on this work by developing a Cu(bphen)(Xantphos)BF₄-catalyzed E → Z isomerization that extends beyond polarized alkenes and does not require oxazolidinone for additional coordination.