Computational approaches to molecular design in surface and organometallic chemistry

Density functional theory calculations were used to investigate the reactivity and interactions of small molecules on the diamond(100)-2 x 1 and silicon(100)-2 x 1 surfaces. The oxidation reactivity of a chromium oxo complex was also studied using computational methods. In all studies, theoretical results were compared to experimental data obtained through collaborations with other researchers, in order to provide a complete picture of the chemical system.; The behavior of adsorbed hydrogen on diamond was examined to identify unexpected features of the experimental IR spectrum. A detailed investigation of interadsorbate interactions was conducted. Based on this analysis, the unexplained peaks, which had a significant effect on the shape of the spectrum, were attributed to adsorbed hydrogen atoms at step and defect sites.; Cycloaddition reactions of 1,3-butadiene with diamond were investigated to determine reaction energetics, and to identify experimentally observed products. These results, compared with the experimental data, suggest a majority [4+2] product with significant competition from the [2+2] product.; The 1,3-dipolar cycloaddition of nitromethane on diamond was also studied. A reaction mechanism for the initial cycloaddition product was calculated, and possibilities for dissociative rearrangements of the nitromethane were evaluated. A comparison of theoretical and experimental data allowed a qualitative assignment of the experimental XPS peaks.; Recent experimental observations have found an unexpected rearrangement of hydrogen and iodine atoms on the silicon surface after annealing. Theoretical results were compared to experimental infrared spectra to identify the spectral peaks. This comparison provides evidence that the rearrangement of the hydrogen and iodine atoms on the surface is kinetically motivated, and not driven by thermodynamics.; The reactivity of a paramagnetic chromium oxo complex, CPCl₂Cr=O, was also investigated using density functional theory. The mechanisms and were compared to determine the extent of competition. The effects of spin-state crossings on the reaction mechanisms were determined, and fully optimized minimum energy crossing point geometries were found. Comparisons were made between reactions with propene, cyclohexene, and 1,4-cyclohexadiene. The relevance of apparent trends to the qualitative prediction of reactivity is discussed.