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Date of Award
Restricted Thesis: Campus only access
Bachelor of Science
Dr. Carol Parish
In most diradical aromatic molecules, the singlet state lies lower in energy than the triplet state. The magnitude of the gap between the two states has important implications in producing the hydrogen-abstracting triplet state. Multi-reference calculations for several didehydropyridines, didehydropyrazines, and didehydrobenzynes from the Parish group at the University of Richmond were compared with single-reference calculations performed on the same molecules by Cioslowski, and Debbert and Cramer. Results suggest the more computationally intensive multi-reference methods predict moderately larger gaps, due to the inclusion of more mathematical flexibility. We also see that the inclusion of nitrogen can cause a decrease in gap size due to multireference triplet state character. The geometries of the nitrogen-containing molecules generated with multi-reference methods show some significant differences from the single-reference calculations for the singlet and for some triplet states. The differences in geometry are all in measures related to inter-radical distance, though the magnitude of difference varies based upon the nitrogen and radical locations. All differences in structure could be attributed to the hybridization of the lone pair from nitrogen with the radical sigma orbitals.
Loucks, Eric A., "A study of the effects of multireference methods on the calculation of energies and electronic structures of nitrogen-containing diradical aromatic systems" (2016). Honors Theses. 935.