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Wasserstoffbrückenbindungen unter Extremen Bedingungen: Kernquanteneffekte und Symmetrisierung der Wasserstoffbrückenbindung untersucht mit 1H-NMR in Diamantstempelzellen

Antragsteller Professor Dr. Leonid Dubrovinsky, seit 7/2021
Fachliche Zuordnung Physikalische Chemie von Molekülen, Flüssigkeiten und Grenzflächen, Biophysikalische Chemie
Experimentelle Physik der kondensierten Materie
Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Förderung Förderung von 2019 bis 2024
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 421754429
 
Erstellungsjahr 2024

Zusammenfassung der Projektergebnisse

The ultimate aim of the project was to develop methodology 1H-NMR in Diamond Anvil Cells (DACs), and combined it with complementary techniques (first of all with single crystal X-ray diffraction (SCXRD)) in order to study behaviour of hydrogen bonds and, more generally, hydrogen bearing compounds, at megabar pressure range. Developed in framework of the project methodology of high-resolution NMR experiments in DACs using one- and two-dimensional homonuclear decoupling allowed to achieve spectral resolutions better than of the ~1 ppm. That enabled 1H-NMR based high-pressure structural analysis of hydrogen position in different materials above 100 GPa. In-situ high-pressure NMR data on molecular hydrogen in its hexagonal phase I up to 123 GPa at room temperature confirm the presence of ortho-hydrogen at low pressures up to ~70 GPa. At higher pressure a crossover in the nuclear spin statistics from a spin-1 quadrupolar to a spin-1/2 dipolar system have been observed, evidencing the loss of spin isomer distinction. A range of compounds (H2O, δ-AlOOH, δ−(Al0.3,Fe0.7)OOH, (Mg0.88, Fe0.12)(Si0.9, Al0.1)2O6H2) containing linear O-H⋯ O units were investigated by means of high-resolution in-situ 1H-NMR spectroscopy in diamond anvil cells at pressures up to 90 GPa. This pressure range covering their respective H-bond summarization. Pronounced minima have been found in the pressure dependence of the NMR resonance line-widths associated with a maximum in hydrogen mobility, precursor to a localization of hydrogen atoms. These minima, independent of the chemical between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of 2:443(1) Å. environment of the O-H⋯ O unit, can be found in a narrow range of oxygen oxygen distances between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of 2:443(1) Å. Goethite, α-FeOOH, is a major phase among oxidized iron species, commonly called rust. We studied the behavior of iron (III) oxyhydroxide up to 81 GPa and 2100 K using in situ synchrotron single-crystal X-ray diffraction. At high pressuretemperature conditions FeOOH decomposes forming oxygen rich fluid and different mixed valence iron oxides (previously known phases of Fe2O3, Fe3O4, Fe5O7, and novel Fe7O10 and Fe6.32O9). Rust is known to form as a byproduct of anoxygenic prokaryote metabolism that took place massively from about 3.8 billion years (Ga) ago until the Great Oxidation Event (GOE) ~2.2 Ga ago. Rust was buried on the ocean floor and was transported into the mantle as a consequence of plate tectonics (started ~2.8 Ga ago). Our results suggest that recycling of rust in Earth’s mantle contributes to redox conditions of the early Earth and formation of oxygen-rich atmosphere. In course of the project, we also studied formation of yttrium hydride phases at pressures over 150 GPa, investigate behavior of methane at conditions of giant planets interiors, and discover CaC2 and Ca3C7 with deprotonated polyacene- and para-poly(indenoindene)-like nanoribbons as products of chemical reactions of calcium carbide and paraffin oil.

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