| Before a universal theory explaining the characteristics of a class of materials can be developed, there is always a need to establish a basis set of correlations between functionalities and the actual physical and electronic structure of these materials. In most circumstances, while it is simple to determine the physical structure of the material the electronic structure is much more complex leading to difficulty in elucidation. Chemical responses observed are heavily based on the electronic interactions and, hence, any exploration along this avenue is entirely useful for a chemist.; This research focusses on two main areas: (a) The support effects and metal-metal interactions in the supported metal oxide catalyst precursor Ni,Cu/Al{dollar}sb2{dollar}O{dollar}sb3{dollar}, and (b) The electronic interactions which help in structural stabilization of the {dollar}alpha{dollar}-keggin unit, including the support and substitutional effects. In both instances, there is a fair knowledge of the reactivity and chemical nature, while there is little information about the molecular and crystal orbital interactions that generate their behavior.; Two main techniques were used to achieve these objectives, namely Electron Paramagnetic Resonance Spectroscopy, and Molecular and Crystal Orbital Calculations based on the extended Huckel Formalism. These were supported by a battery of other techniques for structural and phase separation determination, including Infrared Spectroscopy, Thermal Gravimetric Analysis/Differential Scanning Calorimetry, and Powder X-ray Diffraction. The two main techniques were demonstrated to be complementary in such studies.; It was shown that in the bimetallic materials, there was a significant level of metal-metal interaction possibly facilitated through the support. This strongly affected the adsorption characteristics of the material as demonstrated by adsorption of CO onto the metal covered trigonal surface of the alumina. The catalytic behavior and activity of the ceramic material can therefore be predicted after extension of this study. The {dollar}alpha{dollar}-keggin unit was shown to be structurally stable in spite of metal ion substitution, central ion replacement, and reduction. This behavior is affected by support interactions where a unique exchange process is observed and argues in favor of a high level of electronic delocalization enhanced by cluster-support interaction. From this information a better more stable catalytic material may be produced where the high activity of the keggin unit is preserved. |
