Modern and Classic Quantum Chemistry: Modeling Rhodium-Catalyzed Hydroacylation with Advanced Tools and the Development and Application of Software to Examine Simple Bonding Interactions in a Basis of Molecular Fragments

Abstract

In this dissertation, both modern and classic computational methods are utilized to examine two problems of interest in the field of chemistry. The first problem involves a complex rhodium-catalyzed hydroacylation reaction forms two ketone products. Interestingly and unexpectedly, the major product is the larger, more highly that structured ketone that results from dimerization. A detailed analysis of the reaction mechanism reveals that subtle, non-bonded dispersive interactions play a critical role in the reaction, and that a sophisticated application of the theory is required to reproduce the experimental findings. Specifically, the nudged elastic band and improved dimer methods are applied within the framework of density functional theory and a functional is employed that captures dispersive interactions to map out the reaction pathways. The second problem involves the classical analysis of simple bonding interactions within a test set of molecules. Computer software is developed to transform output from routine ab initio calculations in the atomic orbital basis into a basis of chemically meaningful fragment molecular orbitals. Molecular orbital diagrams are constructed for three prototypical systems: a simple inorganic complex to demonstrate bonding interactions between Lewis acids and bases, an alkene-coordinated squareplanar organometallic complex to highlight the driving force behind the preferred perpendicular orientation of the ligand, and a model of hemoglobin combining with small diatomic molecules to compare the binding characteristics of each.