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Nanosized porous molecular metal oxides with functionalizable cavities and soft matter behaviour allow studies of new phenomena

Final Report Summary - NANOOXIDES (Nanosized porous molecular metal oxides with functionalizable cavities and soft matter behaviour allow studies of new phenomena)

In a recent paper it is stated that “...the gigantic POMs have served as perfect physical models to understand some fundamental science problems,...” (P. Yin et al., J. Am. Chem. Soc. 2016, 138, 2636-2643). They are at least extremely valuable for nanoscience. This is particularly true for those that have been implemented in the project “Nanooxides”. The achievements refer to the behaviour of matter at the nanoscale which is different than under bulk conditions and is of interest in biological contexts. New discoveries have been made possible through the use of our unique spherical metal oxide based capsules equipped with 20 highly active and gateable pores/channels and easily derivatizable interiors. The newly available {Mo132}-type capsule with 30 internal carbonate ligands plays a key role in our current studies as it proves to be quite reactive due to easy release of CO2 upon mild acidification in aqueous solutions: this provides a convenient entry point to the entrapment of weakly coordinating ligands (e.g. fluoride) and to the generation of highly reactive coordinatively unsaturated Lewis acid centers, thus offering the option to perform novel chemistry (e.g. extension of the molybdenum oxide skeleton via condensation processes) using the capsule as a nanoreactor. In parallel, the study of interactions of the sulfate type capsule with biologically relevant cations was continued while it was especially proven that this capsule shows an unprecedented affinity towards the biologically important Ca2+ ions which interact in fully or partially hydrated forms with different well-defined internal and external areas via direct coordination and/or hydrogen bonds. Especially important results relate to the hydrophobic effect (e.g. the tendency of hydrophobic substances to aggregate in water solutions), which is ubiquitous and plays a key role in stabilizing biological structures but also to practical applications in our everyday life (e.g. cleaning of laundry, waterproof clothes and anti-rain window panes). One outcome refers to the stepwise growth of a structurally well-defined organic aggregate within a {Mo132}-type capsule, which has allowed to develop an unprecedented experimental concept providing an important insight into the related hydrophobic self-assembly process and promising to be applicable to a variety of systems. Another outcome relates to water repellency in appropriately constructed hydrophobic capsules while the encapsulated water forms, figuratively speaking, a hovering drop and behaves such that there is a minimum contact with the surrounding hydrophobic wall. This provides a molecular view on dewetting which is a topic of considerable practical importance (see above).