Date of Award
Doctor of Philosophy (PhD)
Adam C. Whalley
Polycyclic aromatic hydrocarbons (PAHs) have shown great promise to produce new organic electronic materials. The networks of delocalized π-electrons present in these conjugated molecules allow for the mobilization of charge carriers. Compared to traditional electronic devices, this new class represents a more sustainable, lower cost, and solution processable alternative. Instability and poor intermolecular interactions are two key challenges preventing widespread adoption of said organic devices. However, the synthetic nature of organic molecules allows for fine tuning of electronic properties, offering a solution to these issues. Introduction of contorted conformations and heteroaromatic rings to PAH systems are discussed within this document as two methods of improving the properties of organic semiconductor materials.The [n]helicenes and [n]circulenes represent two classes of contorted, ortho-fused acene systems. [n]Helicenes are helically chiral structures, in which n denotes the number of fused acene rings present in the helix. The optical properties of helicenes are chirality-dependent, however, smaller helicenes (n < 5) possess low racemization barriers and interconvert rapidly at room temperature. Using a diary ketone-based synthetic approach, we successfully imparted conformational stability to a helicene system with a ridged tether. In the second class of molecules, the [n]circulenes, n denotes the number carbon atoms present in a central ring on which acene rings are fused. Three conformations arise dependent on n: n < 4 is bowl shaped, n = 6 is planar, and n > 6 is saddle shaped. We applied the same diaryl ketone synthetic methodology to access larger circulenes, which was ultimately unsuccessful. The progress and limitations of this diaryl ketone methodology is presented herein. Benzothieno[3,2-b]benzothiophene (BTBT) and its derivatives compose one of the best preforming classes of organic semiconductors. Functionalization of these molecules has resulted in substantially improved device properties, however, substitution at positions other than 2,7 has been largely unexplored. Our work represents a simple, yet high yielding, synthesis of two ditriflate-BTBT derivatives. The utility of the triflate synthetic handles as coupling partners was assessed, affording several novel hexylthiophene-BTBT derivatives with broader implications of allowing access to a multitude of BTBT derivatives. The work presented herein describes the successful synthesis of 2,7- ditriflateBTBT, 3,8-ditriflateBTBT, and three hexylthiophene derivatives. Additionally, the unexpected inversion of the 2,7-BTBT core is reported and its mechanism explored.
Number of Pages
Dyer, Adam M., "Synthesis and Characterization of Highly Contorted Aromatics and Semiconducting Thioacenes" (2021). Graduate College Dissertations and Theses. 1322.
Available for download on Wednesday, December 07, 2022