CRC 1109/1: Oxo Frameworks in Molecular Compounds: Early Stage Modelling, Tailored Structural Motifs for Novel Materials and Water Reactivity (SP A04)

This project will deal with well-defined molecular metal oxo compounds, which are synthesised/trapped to investigate their properties, their (water) reactivity and their dissolution/degradation behaviour. On the one hand we anticipate to thereby gather information on the early stages of oxide formation, on the other hand we study these molecular entities as models for more extended oxide surfaces to gain insight into the properties of certain functions and units on the molecular level. Hence, the controlled construction of Si-O-Al(Fe) frameworks starting from prearranged siloxane-based templates is envisaged, targeting on both molecular cut-outs of known solids and minerals but also on novel compositions, electronic situations and structural motifs (unprecedented ring-sizes, metal arrangements and cages). Suitable candidates will then be investigated with respect to their chemical behaviour in solution and in the gas phase (within A05 and D01). For instance, oxygen exchange with water will be explored in cooperation with A01, and protons as well as hydroxide will be added to elucidate defect generation and dissolution events on the molecular level. Furthermore, such investigations will reveal, how to proceed to reach aggregation and nucleation studied in cooperation with projects like A02, B03 and B04. In case of novel precursors this is expected to lead to materials with new types and thus new properties of structures of functional sites. To mimic the situation in minerals also the behaviour of such molecular compounds in contact with ions – that is, their properties as „ligands“ – will be studied. A further goal is the investigation of defined hydrolysis reactions of precursor complexes dissolved in aprotic solvents with water being carefully dosed through the employment of compounds delivering water in a controlled fashion. This is anticipated to lead to novel, molecular aluminium, silicon and iron oxo aggregates, potentially stabilized by complex metal fragments or additional ligands, which will be investigated structurally and also with respect to their chemical behaviour (as described above) in particular focussing on their functional groups.