The subject of this dissertation is the use of electronic structure calculations to examine and supplement the experimental observations of three different chemical systems. The first topic is the study of pyrogallol[4]arene with R-groups R=H and R=phenyl (ph). This macrocycle self-assembles into dimeric and hexameric nanocapsules. The purpose of this study is to use DFT methods to gain knowledge of this process. While several conformations of pyrogallol[4]arene are thermodynamically stable, experimental evidence suggests that aryl-substituted pyrogallol[4]arene exists in the Chair conformation. During the formation of the nanocapsules, the Chair isomer must convert to the Cone isomer. The relative energies of different structures and their solvent interactions are examined to better understand the process by which self-assembly of the nanocapsule occurs.

Ligated vanadium oxides have generated interest from many fields due to their unique catalytic properties. These systems can be induced to either donate or accept electron density through control of the ligand field and charge on the metal center. In the second study, electrospray ionization mass spectrometry, DFT and conventional ab initio calculations are used to study the addition and ligand-exchange reactions of vanadium oxide cations. Specifically investigated is the addition of H₂O and O₂ to vanadyl complexes of the form [VOX(NCCH₃)]⁺ where X = F ⁻, Cl⁻, Br⁻, I ⁻, and OH⁻. Changing the identity of X allows the observation of how the electron density on the metal center influences the addition of H₂O or O₂. The results of different DFT methods suggest the need for higher-level single-point calculations.

The final chapters discuss the high-level quantum chemical calculations performed to study the structure and energetics of isomers of CH₂BF on both the singlet and triplet PES. MP2 optimizations were used to identify minima and transition states. A series of CCSD(T) single-point calculations were used to extrapolate to the complete basis set limit. A wide variety of structures with a large range of energies were found. All of these species on both PES’s are compared as well as the transition states that connect the most stable isomers. For the singlet system, comparison was made to the previously studied protonated counterparts of the species, [B, C, F, H ₃]⁺.