Two-Coordinate Coinage Metal Complexes as Solar Photosensitizers

Generating sustainable fuel from sunlight plays an important role in meeting the energy demands of the modern age. Here we report the synthesis of new two-coordinate, molecular Cu(I) and Au(I) complexes that were designed to absorb visible photons (vis > 103 M-1cm-1), maintain long excited state lifetimes (~1-0.1s), and perform stable photo-induced charge transfer to a target substrate with remarkably potent photoreducing capabilities (E+/* up to 2.33 V vs. Fc+/0). The photoredox performance was evaluated in a variety of solvents, and we were able to understand the influence of ligand design and metal center on the photophysical properties. Interestingly, we found that the Cu(I) systems have competitive figures of merit with widely used scarce metal photosensitizers such as Ru(bpy)32+ and Ir(ppy)3. This work illuminates two-coordinate coinage metal complexes as promising, abundant metal, solar fuels photosensitizers that offer exceptional tunability and photoredox properties.