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Efficient Photochemical Dihydrogen Generation Initiated by a Bimetallic Self-Quenching Mechanism

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journal contribution
posted on 27.09.2016, 00:00 by Matthew B. Chambers, Daniel A. Kurtz, Catherine L. Pitman, M. Kyle Brennaman, Alexander J. M. Miller
Artificial photosynthesis relies on coupling light absorption with chemical fuel generation. A mechanistic study of visible light-driven H2 production from [Cp*Ir­(bpy)­H]+ (1) has revealed a new, highly efficient pathway for integrating light absorption with bond formation. The net reaction of 1 with a proton source produces H2, but the rate of excited state quenching is surprisingly acid-independent and displays no observable deuterium kinetic isotopic effect. Time-resolved photoluminescence and labeling studies are consistent with diffusion-limited bimetallic self-quenching by electron transfer. Accordingly, the quantum yield of H2 release nearly reaches unity as the concentration of 1 increases. This unique pathway for photochemical H2 generation provides insight into transformations catalyzed by 1.