Phosphine Evaluation on a New Series of Heteroleptic Copper(I) Photocatalysts with dpa Ligand [Cu(dpa)(P,P)]BF4

Five new heteroleptic copper(I) complexes (C1-5) of the type [Cu(dpa)(P,P)]BF4 based on dipyridylamine (dpa) as N,N ligand and commercial diphosphines as P,P ancillary ligands have been synthesised through a simple methodology with high yields. All complexes were thoroughly characterised by spectroscopic and spectrometric techniques, as well by theoretical calculations. These showed Metal to Ligand Charge Transfer (MLCT) absorptions in the 300-370 nm region, and emission in the 450-520 nm region with quantum yields and lifetimes that depend on the nature of the P,P ligand. The photocatalytic performance of copper(I) complexes C1-5 was evaluated for their use as photoredox catalysts in ATRA reactions, decarboxylative coupling and an Appel-type reaction. The use of readily available dpa as N,N ligand constitutes an attractive alternative to the well-established phenanthroline ligands typically used in photocatalysis.