Recent developments of photoactive Cu(I) and Ag(I) complexes with diphosphine and related ligands

In the past two decades, emissive Cu(I) complexes have been synthesized with various ligands, revealing their interesting and useful photophysical properties such as high luminescence efficiency, thermally-activated delayed fluorescence, stimuli-responsive emission, and excellent photochemical properties. Some of these properties have been utilized in applications in light-emitting devices, sensors, and photocatalytic reactions. Following the development of emissive Cu(I) complexes, studies on Ag(I) complexes have revealed that strongly-emissive Ag(I) complexes can also be obtained using various ligands such as Cu(I) complexes. In this article, emissive Cu(I) and Ag(I) complexes with P-P bidentate ligands are assembled, and the relationship between their photophysical properties and the characteristics of ligands is discussed. Solvent-free synthesis of emissive Cu(I) complexes, which has a significant impact on the practical applications and utilization of Cu(I) complexes in photochemical reactions, is also reviewed.