Solid-State 17O NMR, Crystallographic, and Computational Studies of Epoxides and Related Molecules

Abstract

The aim of this thesis was to study quadrupolar nuclei using solid-state 17O NMR spectroscopy, X-ray crystallography, and computational methods. This thesis reports the successful synthesis and characterization of three 17O-labelled epoxides, [17O]-(2S*,3S*)-2,3-bis(4-nitrophenyl)oxirane, [17O]-(2S*,3R*)-2,3-bis(4-nitrophenyl)oxirane, and [17O]-2,2,3-triphenyloxirane. The 17O NMR tensors (measured using solid-state 17O NMR spectroscopy and calculated using computational methods) and structural parameters (measured using single crystal X-ray crystallography and calculated using computational methods) of the three epoxides were compared. The dependence of ethereal 17O NMR tensors on bond geometry was computationally analyzed. A new model for visualizing quadrupolar coupling tensor components using valence p-orbital population anisotropies was also developed. This model is a simple adaption to the Townes-Dailey method that allows for the visualization of each quadrupolar coupling tensor component (χii ii = xx, yy, zz) using only a single parameter (ΔPii), whereas the traditional Townes-Dailey method requires three parameters. This new model was demonstrated to deliver comparable quadrupolar coupling tensor components to those calculated using direct g09 NMR calculation methods for 14N, 17O, and 127I. Finally, iodosylbenzene, a candidate for containing the strongest halogen bonds, was studied using solid-state 17O NMR and computational methods. Using computational methods, its σ-hole was quantified and its magnitude was compared to that of other halogen bond donors.