Binding principles of silicic acid by carbohydrates

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Carbohydrates are suitable chelating ligands for silicon to establish hydrolytically stable Si¿O¿C bonds. In this field ¿hypervalent¿ silicon complexes (coordination number five and six) are stable in strongly alkaline solution but unstable under the conditions of a physiological pH value and therefore they should possess no relevance in the biochemistry of silicon. Thus it is the aim of this project to synthesise (hydrolytically stable) tetracoordinate carbohydrate-silicon compounds, Si(OR)4, representing novel Si1 building blocks for biomimetic production of silica derivatives as possible transport forms in biochemistry. One part deals with the recognition of rules and concepts for synthesising such species in order to gain insight into the principles of their structure and bonding, including the establishment of suitable spectroscopic methods for their detection (in particular by NMR methods). A second part should prove the usefulness of the knowledge gained in the biochemistry of silicon, that is, each newly recognised motif shall be tested on real biomolecules. Our strategy to synthesise the species of interest is to provide carbohydrate-based O-atom patterns that ensure chelation of silicon without any strain. According to DFT calculations, there is enough evidence that such structures should be obtainable.