Date of Award
Doctor of Philosophy
Organic-based electronic devices have received considerable attention because of their presumable advantages over traditional inorganic-based electronics, such as low cost, flexibility, and applicability for large area production. Because of the possible commercialization of electronic products based on organic conducting materials, it is important to develop a variety of organic semiconductors (OSCs) that are categorized as hole transporting (p-type), electron-transporting (n-type) or ambipolar transporting (both hole and electron). P-type OSCs have been the most thoroughly studied. N-type semiconductors are much less common and the charge carrier mobilities have lagged considerably behind their p-type counterparts. Fullerene-based materials are currently the most widely used n-type semiconductors in OPVs. The cage-like structure associated with buckminsterfullerene is made of fused six- and five-member rings. Acenaphthylene is a basic fragment of C60 and has shown potential as a valuable building block for n-type OSCs. To utilize this promising structure, the acenaphthylene unit has been incorporated into a variety of molecular structures to produce both small molecule and polymeric materials. We started with the study of fully unsaturated tetraquinane derivatives, which contain four linearly fused five-membered rings. The desired diacenaphthylpentalenes were synthesized via a palladium-catalyzed dimerization of 1-iodo-2-arylethynyl-acenaphthylenes. The compounds are benchtop and solution stable and behave as hole-transporting or ambipolar semiconductors in organic field effect transistors. The X-ray crystal structure demonstrates the importance the fused naphthalene units as they stabilize the pentalene core with an extended π-framework. The tetraquinane derivatives possess high optical gap materials owing to a forbidden HOMO to LUMO transition, yet have narrow electrochemical gaps and are reduced at small negative potentials giving lowest unoccupied molecular energy levels of -3.57 to -3.74 eV. In addition to the unsaturated tetraquinane derivatives, this thesis also includes work on the creation of macrocycles containing acenaphthylene or cyclopenta[cd]perylene units. The stabilized annulenes, with rigid and π-conjugated structures, have potential application as discotic liquid crystals and porous organic solid. 1H NMR and low resolution mass spectra gave solid proof that a target macrocycle was synthesized; however, the tedious work up and limited purification techniques did not enable large scale synthesis. The investigation of new donor-acceptor copolymers incorporating acenaphthylene or cyclopenta[cd]perylene units was also explored. Since the molecular scaffolds of the desired polymers have structural resemblance and electron affinities compared to bis-imide rylene dyes (NDI and PDI), the resulting materials have relavence for a varety of OSC based devicse. UV-Vis spectroscopy and cyclic voltammetry were utilized to probe the photoelectronic properties of these materials.
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