Nuclear-Electron Correlation Effects and Their Photoelectron Imprint in Molecular XUV Ionisation.

The ionisation of molecules by attosecond XUV pulses is accompanied by complex correlated dynamics, such as the creation of coherent electron wave packets in the parent ion, their interplay with nuclear wave packets, and a correlated photoelectron moving in a multi-centred potential. Additionally, these processes are influenced by the dynamics prior to and during the ionisation. To fully understand and subsequently control the ionisation process on different time scales, a profound understanding of electron and nuclear correlation is needed. Here, we investigate the effect of nuclear-electron correlation in a correlated two-electron and one-nucleus quantum model system. Solving the time-dependent Schrödinger equation allows to monitor the correlation impact pre, during, and post-XUV ionisation. We show how an initial nuclear wave packet displaced from equilibrium influences the post-ionisation dynamics by means of momentum conservation between the target and parent ion, whilst the attosecond electron population remains largely unaffected. We calculate time-resolved photoelectron spectra and their asymmetries and demonstrate how the coupled electron-nuclear dynamics are imprinted on top of electron-electron correlation on the photoelectron properties. Finally, our findings give guidelines towards when correlation resulting effects have to be incorporated and in which instances the exact correlation treatment can be neglected.

Sustainable and highly controlled aryl couplings revealed by systematic assessment of photoactivatable linkers.

The controlled synthesis of biphenyls, which play a prominent role in pharmaceuticals, agrochemicals, and liquid crystals, typically requires hazardous organometallic reagents, aryl halides, and heavy metal catalysts. We recently reported a metal-free, photochemical alternative ("photosplicing") for the selective preparation of a wide range of pharmaceutically important biphenyls. Whereas the traceless sulfonamide linker enables and controls the aryl coupling, unwanted toxic byproducts are released. Therefore, we designed over 25 different temporary linkers and tested them for their suitability for the photosplicing reaction in a flow reactor. We found that a surprisingly high number of functional groups enable light-induced aryl fusion and identified a number of linkers for environmentally friendly procedures. We also report that a thiol-ene (click) - photosplicing sequence enables a convenient route to biaryls such as liquid crystals. This work sheds light on thus far neglected photochemistry of temporary linkers, reduces toxic byproducts, and expands the available starting materials for metal-free biphenyl synthesis.

Hydrogen Production at a NiO Photocathode Based on a Ruthenium Dye-Cobalt Diimine Dioxime Catalyst Assembly: Insights from Advanced Spectroscopy and Post-operando Characterization.

The production of hydrogen by efficient, low-cost, and integrated photoelectrochemical water splitting processes represents an important target for the ecological transition. This challenge can be addressed thanks to bioinspired chemistry and artificial photosynthesis approaches by designing dye-sensitized photocathodes for hydrogen production, incorporating bioinspired first-row transition metal-based catalysts. The present work describes the preparation and photoelectrochemical characterization of a NiO photocathode sensitized with a phosphonate-derivatized ruthenium tris-diimine photosensitizer covalently linked to a cobalt diimine dioxime hydrogen-evolving catalyst. Under simulated AM 1.5G irradiation, hydrogen is produced with photocurrent densities reaching 84 ± 7 µA·cm-2, which is among the highest values reported so far for dye-sensitized photocathodes with surface-immobilized catalysts. Thanks to the unique combination of advanced spectroscopy and surface characterization techniques, the fast desorption of the dyad from the NiO electrode and the low yield of electron transfer to the catalyst, resulting in the Co demetallation from the diimine dioxime framework, were identified as the main barriers limiting the performances and the stability of the system. This work therefore paves the way for a more rational design of molecular photocathodes for solar fuel production and represents a further step toward the development of sustainable processes for the production of hydrogen from sunlight and water.