Icy satellites of Jupiter and Saturn are the only extra-terrestrial planetary bodies where the presence of liquid water has been discovered in a form of subsurface oceans. Subsurface oceans are nowadays the most appealing astrobiological targets and became the focus of diverse interdisciplinary research as well as of upcoming space missions. While a variety of volatile compounds (CO2, CH4, N2, NH3, CH3OH, etc) are expected to be present in significant amount in the oceans of icy satellites of Saturn and Jupiter, they should be stable in the form of gas clathrate hydrates at relevant high-pressure and from low- to temperate-temperature conditions. Clathrate formation and destabilization govern the volatile reservoir and chemical exchange in the interior, and have a major impact on the ocean composition, evolution and astrobiological potential. Despite being the main reservoir of volatiles in large ocean worlds, our knowledge on stability and properties of chemically relevant clathrate hydrates at relevant thermodynamic conditions is very limited. To address the mineralogy, evolution and astrobiological potential of extra-terrestrial oceans and to provide data critical for preparing the future space missions, the current proposal aims exploring multicomponent clathrate hydrates in a wide range of pressures, temperatures and compositions by using in situ single-crystal X-Ray diffraction and Raman spectroscopy at high pressures and low to ambient temperatures.

Photoreceptor proteins regulate adaptation of living organisms to light. A class recently discovered uses a vitamin B12 derivative to sense green light and regulate the biosynthesis of carotenoids, which protect against photo-oxidative damage. CarH is a prototype of this class. Its sophisticated machinery has been proposed as a promising optogenetic tool, yet its design and optimization requires detailed knowledge of the molecular mechanism in real time. Structural and spectroscopic data on CarH suggest a complex photochemical and structural pathway in the picosecond-to-second time scale connecting photon absorption to major quaternary changes. We propose to provide a molecular description of CarH gene regulation mechanism by using the new tools for structural biology available at advanced X-ray sources (synchrotrons and free electron lasers). The results will enable to uncover the structural basis of light-dependent gene regulation by one of Nature’s most complex metallo-cofactors.

Multicross aims at understanding transition metal photophysics to a new level of detail thanks to a joint experimental and theoretical research program spanning three laboratories and two countries. Ultrafast optical spectroscopy and X-ray techniques will be pushed to time resolutions approaching 10 fs. Quantum models will be used to solve time dependent Schrodinger equation to follow the photoinduced wavepacket motion and dispersion along different excited state trajectories that will be controlled by different pump laser pulses. Because the same physical model will be able to explain the different experimental findings, the outcomes will be little biased and the resulting representations can be used to clarify the mechanisms behind the unexpected properties of ultrafast intersystem crossing of transition metal compounds. Indeed transition metals play often a central role in photoreceptors, catalysts and biological active sites. This is due to their capability of changing oxidation states (favouring charge transfers) and of being coordinated by different molecular geometries. Typical examples are organometallic systems. Organic ligands lift the degeneracy of 3d orbitals usually resulting in non bonding and antibonding levels. Such energy gap creates different electronic/structural configurations that can be stabilized by enthalpic (low spin, LS) or entropic (high spin, HS) contributions. Spin CrossOver (SCO) from LS to HS state is usually phototriggered by electronic excitation via a metal-to-ligand charge transfer (MLCT) band. Experiments have tried to disclose what immediately follows these excitations and have delivered unexpectedly high intersystem crossing rates. Such observation spurred a wealth of experimental and theoretical investigations all attempting to understand the sub picosecond (1 ps = 10-12 s) LS to HS mechanism and dynamics. Today, while the ultrafast nature of SCO photophysics is undiscussed a detailed understand of the process is still debated. For example, the most studied SCO compound has been scrutinised with optical and X-ray spectroscopy, still yielding completely different switching mechanisms in terms of time scale (from sub-50-fs to nearly 200 fs) and visited intermediates electronic states. The physical picture is even less clear for non octahedral SCO systems that only very recently have been experimentally studied, or hetero-bimetallic compounds in which both charge transfer and spin transition characterize the the difference between low and high temperature phases. Multicross will focus on those different systems in search of an underlying physical picture that could for example evidence the role of particular structural degrees of freedom in driving the system to the metastable HS state.

MXenes are widely recognized as one of the fastest growing areas in 2D materials research due to their exceptional physical and structural properties and great promise for various applications, including spintronics and magnetic sensors. Yet, the experimental efforts towards their magnetism remain very limited since Fe, Co or Ni are incompatible with MAX phases that are used as precursors to produce MXenes via selective chemical etching of the A layer. Alternatively, to master magnetic properties of 2D MXenes, we propose to intercalate Fe into few layered MXene structures in ultrahigh vacuum (UHV) conditions at variable temperatures. Producing MXenes with various surface functional groups (-F, -OH, =O, -Cl, -Br) and a detailed study of their thermal desorption will allow to obtain partially or almost unfunctionalized MXenes in a very controlled manner. The unterminated surface of various MXenes (Ti3C2, Ti2C) will be functionalized by in-situ deposition of Fe, which will be further intercalated at different temperatures and in-situ monitored by Auger spectroscopy. Such functionalization by intercalation could enable creation of MXenes with novel 2D magnetic properties. The comprehensive study of the structure-magnetism relation of Fe-intercalated MXenes is the focus of the project. The combination of synthesis and characterization of various MXenes chemistry at the Materials and Physical Engineering Laboratory (LMGP, Grenoble) together with atomic scale investigation and magnetic characterization in UHV environment at the University of Duisburg-Essen (UDE, Duisburg) and element-selective hard X-ray polarization dependent spectroscopy in high magnetic fields at the European Synchrotron Radiation Facility (ESRF, Grenoble) will provide a turning point in establishing reliable implementation routes for magnetic MXenes.