Novel Approaches to the Formation and Reactivity of Compounds with Silicon-Silocon-Bonds - COORDINATION PROJECT

Elemental silicon, silicon-containing materials and molecular silicon compounds are equally important in chemistry, physics and materials science. They have decisively contributed to scientific and technical progress. The goal of the Austrian Forschungsschwerpunkt is to develop and optimize new approaches and strategies for the deliberate synthesis, transformation and modification of solid, polymeric or molecular silicon-containing compounds and materials. The preparative work is supported by physical-chemical and theoretical investigations. The Forschungsschwerpunkt concentrates on two particularly topical issues: molecular and polymeric compounds with Si-Si bonds (di- and oligosilanes, silicon clusters, polysilanes) on one hand, and nano- and mesostructured silicon-containing solids (siloxene, SiO, mesoporous silicates) on the other hand. Silicon resembles carbon in the ability to form molecular and polymeric compounds with covalent homoelement bonds. However, oligo- and polysilanes are semiconducting along the Si-Si chain. Two-dimensional systems with a Si-Si skeleton are hardly known. They should have very interesting chemical, electrical and optical properties. The same is expected for molecular silicon clusters. The controlled increase of the dimensionality of systems with Si-Si bonds starting from monomeric compounds or small oligomers, or the degradation of solids with three- dimensional Si-Si (sub)structures is highly interesting, because a continuous change of the electronic structure and thus of the physical and chemical properties can be expected upon changing the dimensionality of the Si-Si framework. Methods to incorporate organic or inorganic functional groups into compounds with Si-Si bonds are hardly available, although their spectrum of properties could be additionally widened by such modifications. The deliberate creation of nano- and mesostructured solids has experienced a rapid development in the last few years, and silicon-oxygen compounds played an important role. In silicon chemistry there are two solid compounds known for a long time and being technically interesting: siloxene and solid silicon monoxide. Their structural composition is still not completely elucidated. Both contain both Si-Si and Si-O bonds, but their mutual arrangement in the nanometer regime is still debated. New applications for these compounds and their structure will be investigated by studying their reactivity and by preparing model compounds. Apart from utilizing these "natural" nanostructured compounds, there will be a methodologically new approach to the highly topical area of template-directed synthesis of mesostructured silicate materials. The scientific program of the Austrian Forschungsschwerpunkt is closely connected with the Schwerpunktprogramm "Specific phenomena in silicon chemistry: new experimental and theoretical approaches to the deliberate formation and better understanding of multi-dimensional systems" of the Deutsche Forschungsgemeinschaft and with relevant projects of some research groups in Switzerland. This will considerably improve the scientific and economic efficiency of the national programs and will create synergies.