Polyoxopalladates as Prototype Molecular Hydrogen Uptake Systems and Novel In situ Hydrogen Detectors on the Nanoscale

• Published in: European journal of inorganic chemistry Vol. 2019; no. 3-4; pp. 448 - 455
• Main Authors: Schmitz‐Antoniak, Carolin, Izarova, Natalya V., Svechkina, Nataliya, Smekhova, Alevtina, Stuckart, Maria, Schmitz, Detlef, Kögerler, Paul
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 31.01.2019
• Subjects: Cobalt; Ferric ions; Hydrogen; Hydrogen storage; Hydrogenation; Inorganic chemistry; Magnetic moments; Magnetic properties; Magnetism; Oxidation; Polyoxometalates; X‐ray absorption
• DOI: 10.1002/ejic.201800972
• ISSN: 1434-1948

Dodecapalladium(II) oxide‐based molecular nanocubes encapsulating Fe3+ (3d5) or Co2+ (3d7) ions display facile hydrogen uptake with concurrent pronounced magnetization changes that suggests use as molecular hydrogen detection materials. Electronic and magnetic properties were investigated element‐specifically by X‐ray absorption spectroscopy and its associated magnetic circular and linear dichroisms. Hydrogenation reduces the Fe3+ (3d5) ions to a 3d6 state while the Co2+ 3d7 configuration remains largely unaffected. However, in both cases, drastic changes of the crystal field and the magnetic properties were observed and quantified. The spin magnetic moments in the as‐prepared state were obtained to be similar to the ones expected for free ions and are reduced significantly by about 30–40 % for both Fe and Co central ions upon loading with hydrogen. In addition, re‐oxidation and hydrogenation in a second cycle were monitored and the sensitivity to hydrogen and oxygen exposure as a function of the peripheral capping groups is discussed. The magnetic response of single Fe and Co ions hosted by cuboid polyoxopalladate nanoshells to hydrogenation and oxidation is studied element‐specifically by X‐ray absorption spectroscopy. Huge changes in the magnetic moments of 30–40 % accompanied by a change of the visual impression of the material point towards a possible application in novel hydrogen uptake and detection devices with tunable sensitivity.