| Nuclear Magnetic Resonance (NMR) has become one of the most powerful structural tools available to modern chemists, enabling molecular level probes of structure, dynamics, and the energetic components of chemical processes. However, much of the data that is taken from the NMR experiment is under-utilized. In particular, it is common practice to use the chemical shift observed simply as an empirical marker for the chemical environment of that nuclei. Yet the chemical shift contains much more information than this, giving detailed information on the local electronic structure around each nucleus. A powerful tool to accurately relate the chemical shift back to local electronic structure is ab initio theory. Ab initio calculations give a direct link from the NMR chemical shift back to the local electronic structure. This forms the underlying framework of this thesis, making use of the next significant figure in the chemical shift to solve problems of molecular structure.;A related goal is how ab initio calculations can enrich the interpretation of energetic information derived from dynamic NMR experiments. In this way, more detailed structural models can be connected to the energetic components that make up the overall energy pathway. This combination of ab initio theory and NMR allows us to obtain information that is often impossible to obtain by other means. In the case of the amide rotational barrier of the pyridine carboxamides, the use of ab initio theory allows us to present a detailed analysis of the energetic components of the process. For the bond stretch isomers of 1,3-dibora-2,4-diphosphoniocyclobutane-1,3-diyl studied, the chemical shift can be used to prove the existence of certain chemically elusive species in solution and to obtain accurate exegetics of the process of the bond stretch isomers inter-conversion. For Vitamin-D3, the combination of correlation spectroscopy in the solid state with advanced ab initio techniques can be used to refine regions of the crystal structure reported as dynamic by x-ray crystallography. |
