Hybrid materials constructed from polyoxometalate clusters

The research presented in this thesis documents efforts to produce varying classes of hybrid inorganic-organic materials based on polyoxometalate (POM) clusters. The versatility and applicability of POMs are based on properties such as reversible oxidation/reduction, organic modification, and metal substitution. All of these characteristics lead to a wide range of applications ranging from catalysis to medicine.; One aspect of this research focused on supporting POM clusters on the surface of inert silica supports for use as heterogeneous catalysts in a solution phase reaction. To minimize the leaching of POM during catalysis, several techniques were developed. The first involved substituting metal sites of the POM for a transition metal (transition metal substituted polyoxometalate - TMSP). This provided a location at which to perform oxidation catalysis as well as bonding. The second modification was to graft ligand groups to the surface of the meso/macroporous and non-porous silica supports. When the TMSP was impregnated onto the ligand functionalized support, the TMSP clusters were anchored to the support surface through dative bonds. These methods were applied to both mono- and tri-substituted TMSP clusters and the catalytic activity of each on various supports was tested by an epoxidation reaction.; Another goal of this research was to build larger structures based on organically modified POMs. The organic groups provided linking points through which to connect the clusters together. By using clusters with well-defined bonding points, a certain amount of geometrical control was introduced. Factors influencing the crystalline architecture of the final product include the organic group, the hydrogen bonding strength of the solvent, and the counterion. Two open-framework structures were synthesized and studied by X-ray diffraction.; Transition metal-POM salts were also used as precursors in the construction of a coordination network. The metal-ligand network occludes the POM cluster directly within the structure. By decorating the framework with chemically interesting anions, the functionality of standard coordination networks was improved.