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Shedding Light on the Nature of Photoinduced States Formed in a Hydrogen-Generating Supramolecular RuPt Photocatalyst by Ultrafast Spectroscopy

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journal contribution
posted on 27.07.2018, 13:05 by Annemarie Huijser, Qing Pan, David van Duinen, Mads G. Laursen, Amal El Nahhas, Pavel Chabera, Leon Freitag, Leticia González, Qingyu Kong, Xiaoyi Zhang, Kristoffer Haldrup, Wesley R. Browne, Grigory Smolentsev, Jens Uhlig
Photoinduced electronic and structural changes of a hydrogen-generating supramolecular RuPt photocatalyst are studied by a combination of time-resolved photoluminescence, optical transient absorption, and X-ray absorption spectroscopy. This work uses the element specificity of X-ray techniques to focus on the interplay between the photophysical and -chemical processes and the associated time scales at the catalytic Pt moiety. We observe very fast (<30 ps) photoreduction of the Pt catalytic site, followed by an ∼600 ps step into a strongly oxidized Pt center. The latter process is likely induced by oxidative addition of reactive iodine species. The oxidized Pt species is long-lived and fully recovers to the original ground state complex on a >10 μs time scale. However, the photosensitizing Ru moiety is fully restored on a much shorter ∼300 ns time scale. This reaction scheme implies that we may withdraw two electrons from a catalyst that is activated by a single photon.