Vortrag

A fundamental challenge for the development of sustainable energy technologies is the
efficient harvesting of solar energy to drive chemical processes. The design of light-driven
artificial catalytic systems usually implies the use of a photosensitizer and a photo-redox
catalyst.1 On the one hand, water oxidation steps are the bottleneck in this machinery, due
to the large energy penalties involved. On the other hand, good photosensitizers should be
able to efficiently populate long-lived triplet states that are required for promoting oxidation
of the catalyst, but this feature is severely hindered at room temperature due to the fast nonradiative
decay to the ground state. Through a close-loop interplay of theory and experiment,
we overcome the challenging task of understanding the underlying mechanisms governing
the performance of catalysts and photosensitizers for photoinduced water oxidation.
On the first part of my talk, I will cover some of the computational mechanistic studies we
have performed in chemically driven water oxidation reactions in solution. Specifically, the
activation mechanism of a bio-inspired Mn-V oxide cluster prior its water oxidation reaction2,3
and the water oxidation catalytic cycle in a series of ruthenium-based catalysts.4
On the second part, I will cover our results in the study of excited states properties of novel
ruthenium-based photosensitizers. Here, we addressed possible reaction pathways that
would contribute to the deactivation of the emitting triplet state of the photosensitizer. These
results are then used to create a quantitative model for the prediction of phosphorescence
life-time, that can be accurately employed for ruthenium phosphors. Furthermore, we unveil
a series of misconceptions related to the interpretation of experimental data of variable
temperature photoluminescence measurements in this family of complexes.

Acknowledgments: This work is funded by the Deutsche Forschungsgemeinschaft
(TRR234 “CataLight”) and the Austria Science Fund through the Catalight Transregio
(project I 3987).

References:
1 M. D. Kärkäs, O. Verho, E. V. Johnston and B. Åkermark, Chem. Rev., 2014, 114,
11863–12001.
2 G. Cárdenas, I. Trentin, L. Schwiedrzik, D. Hernández-Castillo, G. A. Lowe, J. Kund,
C. Kranz, S. Klingler, R. Stach, B. Mizaikoff, P. Marquetand, J. J. Nogueira, C. Streb
and L. González, Chem. Sci., 2021, 12, 12918–12927.
3 J. H. Kruse, M. Langer, I. Romanenko, I. Trentin, D. Hernández-Castillo, L.
González, F. H. Schacher and C. Streb, Adv. Funct. Mater., 2022, 32, 2208428.
4 S. Amthor, D. Hernández-Castillo, B. Maryasin, P. Seeber, A. K. Mengele, S. Gräfe,
L. González and S. Rau, Chem. - A Eur. J., 2021, 27, 16871–16878.