Two-Coordinate Coinage Metal Complexes as Solar Photosensitizers
Collin N. Muniz, Claire A. Archer, Jack S. Applebaum, Anushan Alagaratnam, Jonas Schaab, Peter I. Djurovich, Mark E. Thompson
Abstract
Generating sustainable fuel from sunlight plays an important role in meeting the energy demands of the modern age. Herein, we report two-coordinate carbene-metal-amide (cMa, M = Cu(I) and Au(I)) complexes that can be used as sensitizers to promote the light-driven reduction of water to hydrogen. The cMa complexes studied here absorb visible photons (ε vis > 10 3 M –1 cm –1 ), maintain long excited-state lifetimes (τ ∼ 0.2–1 μs), and perform stable photoinduced charge transfer to a target substrate with high photoreducing potential ( E +/ * up to −2.33 V vs Fc +/0 based on a Rehm–Weller analysis). We pair these coinage metal complexes with a cobalt–glyoxime electrocatalyst to photocatalytically generate hydrogen and compare the performance of the copper- and gold-based cMa complexes. We also find that the two-coordinate complexes herein can perform photodriven hydrogen production from water without the addition of the cobalt–glyoxime electrocatalyst. In this “catalyst-free” system, the cMa sensitizer partially decomposes to give metal nanoparticles that catalyze water reduction. This work identifies two-coordinate coinage metal complexes as promising abundant metal, solar fuel photosensitizers that offer exceptional tunability and photoredox properties.