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Faculty of Graduate Studies

Clayton Smith

  • B.Sc. (University of Victoria, 2024)
Notice of the Final Oral Examination for the Degree of Master of Science

Topic

Graph-Theoretic Modelling of Polarizability in Donor-Bridge-Acceptors

Department of Chemistry

Date & location

  • Tuesday, August 25, 2026
  • 8:00 A.M.
  • Elliott Building, Room 305

Examining Committee

Supervisory Committee

  • Dr. Irina Paci, Department of Chemistry, University of Victoria (Supervisor)
  • Dr. David Leitch, Department of Chemistry, UVic (Member)

External Examiner

  • Dr. Ulrike Stege, Department of Computer Science, UVic

Chair of Oral Examination

  • Dr. Magdalena Bazalova-Carter, Department of Physics and Astronomy, UVic

Abstract

The development of coarse-grained methods offers a promising avenue for cost-effective computational modelling of chemical systems. This work investigates one approach, using a graph-theoretic recasting of the chemical problem to generate descriptors for a quantitative structure property modelling to predict electronic response, specifically polarizability. A collection of small organic molecules known as donor-bridge acceptors are studied here as a means to understand the different aspects of this kind of modelling, as a step towards the future use of the same methods in materials simulations. These molecules consist of three units: an electron donating group (donor), a π-conjugated central group (bridge), and an electron withdrawing group (acceptor) and overall constitute a conjugated organic molecule with interesting responses to electronic fields. The first chapters introduce the graph-theoretic formalism to the extent which it is used in the present work, along with the necessary theoretical machinery and custom software used to construct these models. This software itself is briefly discussed as a means to show the individual steps performed and modelling decisions taken. The first chapter of results (chapter 4) discusses two such decisions. In this graph-theoretic recasting, a common approximation is that hydrogen atoms in the chemical structure are ignored, but the effects are rarely detailed. We find that by all measures used, the exclusion of hydrogen atoms at this step produces better and more efficient models. In addition, a number of different weighting schemes are compared to understand the best ways of including heteroatom and multiple bond effects to our models. The descriptors themselves are then analyzed and general conclusions are drawn about which descriptors perform the well in this modelling and which do not. This leads into a brief discussion of the inter-relatedness of many of these graph-theoretic descriptors. Finally, the chemical structures and polarizabilities are investigated more thoroughly to attempt to understand what chemical and structural features tend to enhance or inhibit the polarizability of donor-bridge-acceptor molecules.

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