Transformations and Photophysical Properties of Organic Molecules

Abstract

In this dissertation we set out to describe the excited state properties of organic molecules as well as the inherent reactivity of organic molecules from a computational perspective. In order to compute excitation energies, we use the particle-particle random phase approximation (pp-RPA) to the pairing matrix fluctuation. We apply the pp-RPA to a set of organic molecules that exhibit thermally activated delayed fluorescence. The charge-transfer excited states are accurately reproduced with the pp-RPA. This class of molecules represent the largest molecules studied with the pp-RPA.We also present method development to mitigate a shortcoming of the pp-RPA. Previously, the pp-RPA approach to computing excitation energies was limited to describing excitations that originate from the highest occupied molecular orbital (HOMO). We adopt a non-optimized pp-RPA reference, which allowed us to compute the valence excitation energies that originate from any orbital below the HOMO. This approach was applied to a set of benchmark organic molecules.With respect to molecular transformations, we provide computational insight to the regioselective hydroamination of unsaturated organic molecules with the aid of density functional theory (DFT). Using concepts from conceptual DFT we uncover that the observed regioselectivity is driven by the inherent reactivity of the organic molecule of interest. Our analysis provides insight into the controllable addition of N―H bond across an unsaturated olefin.