Fourfold versus Sixfold Coordination of the Silicon Atoms in Phosphosilicates: Syntheses, Structures and Consequences for Materials Properties

拟议的项目重点是磷硅酸盐的合成、结构表征和选定的性质。它们含有SiO4-和PO4-四面体以及八面体配位的硅原子。到目前为止，这些材料是在高温或高压下形成的。最近，我们找到了一条用SiO6-八面体合成磷硅酸盐的新路线。其特点是：-在有机溶剂中的无水合成-在室温和常压下。一方面，研究了不同试剂和反应条件对SiO_6-生成的影响。另一方面，具有特定结构特征和组成的磷硅酸盐将通过新型前驱体生成。预计产品将是齐聚物或聚合体。它们将从元素组成、结构和构建块的排列方面进行表征，这将需要广泛使用核磁共振波谱。为了获得尽可能真实的结构模型，将有一个执行量子力学计算的理论小组(P.Kroll，德克萨斯州阿灵顿)参与，其结果将通过光谱和热化学测量进行比较和验证。同时，将对材料性能进行测试。这些特性包括热稳定性和化学稳定性以及光学特性。对磷硅酸盐材料的合成、结构和性能的了解将有助于开发其未来的潜在应用。

The proposed project focuses on the syntheses, structural characterisation and selected properties of phosphosilicates. These contain SiO4- and PO4-tetrahedra as well as octahedrally coordinated silicon atoms. So far these materials were formed under high temperatures or high pressure. Recently, we found a novel synthesis route to generate phosphosilicates with SiO6-octahedra. The characteristics are: -anhydrous syntheses in organic solvents -at room temperature and ambient pressure. On the one hand the research will deal with the dependency of the SiO6-formation on different reagents and reaction conditions. On the other hand phosphosilicates with specific structural features and compositions will be generated via novel precursors. The products are expected to be oligomeric or polymeric. They will be characterized with respect to elemental composition, structure and arrangement of the building blocks, which will require extensive use of NMR spectroscopy. In order to gain structural models which are as realistic as possible a theoretical group (P. Kroll, Arlington, Texas) will be involved who perform quantum mechanical calculations, the results of which will be compared and verified by spectroscopic and thermo¬chemical measurements. At the same time material properties will be tested. These include thermal and chemical stability as well as optical characteristics. The knowledge of syntheses, structures and properties will help to develop future potential applications of the phosphosilicate materials.