Polyoxometalates’ emerging biological applications

Polyoxometalates (POMs) form a large class of polyatomic (transition) metal oxyanions which have a wide range of applications, e.g. in catalysis, as sensors, in biotechnology and nanotechnology, in medicine and materials science. To date, the biological studies are under-represented, as in particular systematic studies about species identification in solution and the interactions of polyoxometalates and proteins are lacking. This continuation project is designed to contribute to the basic molecular understanding of the interaction of different POM basic structures with biomacromolecules when applied in biological systems. New polyoxometalates such as the hexagon sandwich polyoxotungstate, themixed Krebs-type polyoxotungstate,the4f transition-metal-substituted germanotungstate, the Co-substituted germanotungstate, and 3d- transition-metal substituted wheels are in focus. The hexagon sandwich polyoxotungstates and the 4f transition-metal-substituted germanotungstates are investigated towards their ability to act as selective acid phosphatases. The mixed Krebs-type polyoxotungstates represent promising oxidation catalysts. The Co-substituted germanotungstates are efficient water-splitting catalysts and 3d-transition-metal substituted wheels are currently a synthetic challenge. The structures of new polyoxometalates will be investigated by X-ray analysis and spectroscopy. POM-protein complexes are to be examined by X-ray analysis. The results of this project will contribute to a fundamental understanding of both the physical properties of polyoxometalates and their interactions with proteins that are currently lacking. In co-operation with Eder group at TU Vienna, the Co-substituted germanotungstates will be tested towards their ability to cleave water and release molecular oxygen and hydrogen. The studies planned here are subordinated to the thematic focus on climate and energy policy, as the future of our energy generation will play an important economic and political role.

Polyoxometalates (POMs) represent a large class of mostly anionic clusters, which are composed by metals in high oxidation states linked by oxygen atoms resulting in a vast variety of unique structures with possible applications in material science, photochemistry and biological chemistry, including protein crystallography. Lacunary (vacant) POMs can be considered as inorganic, multidentate macroligands towards different electrophiles (e.g. d- and f-block metal ions, organometallic species). This results in a large diversity of POM structures (shape, size, composition, etc.) as well as properties (thermal and oxidative stability, acidity, redox activity, solubility, etc.) and potential applications. This grant project was designed to contribute towards the fundamental understanding of new POM archetypes and structures and their potential in emerging biological applications . The aims of this study was to synthesize new POMs and explore their potential as novel catalysts for applications where new catalysts are urgently needed and POMs are the most prospective candidates. The application of POMs in catalysis is stimulated by their fascinating properties, including tunable acidity and redox properties, inherent resistance to oxidative decomposition, high thermal stability, and impressive sensitivity to light and electricity. These remarkable properties have a close relationship with their structures and compositions. The well-defined atomic connectivity of POMs provides the compositional diversity required by a rigorous assessment of the consequences of composition on catalytic reactivity. For the synthesis of POMs new synthetic pathways had been undertaken. A combination of X-ray structure analysis, electrochemical and magnetic measurements, IR spectroscopy, thermogravimetric analysis (TGA), mass spectrometry and elemental analysis were the methods of choice for characterizing new compounds and to reach the proposed goals.