Understanding intra- and intermolecular interactions in thiophene-containing systems

Intra- and intermolecular organization and interactions in conjugated organic semiconductors play a critical role in the performance of devices fabricated from these materials. In organic field effect transistors (OFETs), for instance, intimate TT-stacking along with suppression of intramoleculardisorder are critical strategies towards maximizing charge mobilities. In contrast, the performance of organic light-emiting diodes (OLEDs) is enhanced by preventing strong intermolecular interactions and aggregation, both of which would otherwise give rise to charge trapping and quenching and by extension poorer device performance. The ability to understand, evaluate, and control intra- and intermolecular organization in a material is therefore invaluable to enhance and tune the electronic properties of a system.;The desire to explore ways in which these interactions can be controlled is the motivation for the molecules synthesized in this dissertation. In Chapter 3, 3,4- phenylenedioxythiophenes (PheDOTs) are introduced as attractive synthons due to their highly planar structures as elucidated from x-ray crystal structures, which could promote TT-stacking interactions. As this molecule has not been thoroughly investigated in the literature, the electrochemical properties of a family of alkyl-substituted PheDOTs are explored and elucidated. Likely owing to the ability of this planar structure to form intimate intermolecular interactions, promising conductivities are measured for freestanding films of electropolymerized pPheDOTs. Additionally, the charge-storage abilities of the electropolymerized films are evaluated and also found to be promising.;In Chapter 4, the effects on intra- and intermolecular organization caused by the presence of PheDOT are more directly investigated. When incorporated into thiophene oligomers and polymers, an improvement in both intra- and intermolecular organization are observed when compared to their all-thiophene analogs. Sulfur-oxygen interactions are believed to lock the system into a more planar conformation; this planarity in turn promotes strong intermolecular interactions. X-ray crystal structures again demonstrate that three-ring systems incorporating PheDOT are highly planar structures with close packing distances. Throughout the chapter, we demonstrate how the absorbance and emission spectra can be powerful tools to elucidate and qualify the intra- and intermolecular interactions present in the system.;In Chapter 5, molecules are designed to deliberately frustrate intermolecular packing. This is accomplished by utilizing spirobiProDOT as a core synthon. Extension of the conjugation through the four active sites on spirobiProDOT followed by electropolymerization of these systems is predicted to give a highly branched, porous and rigid network through which ion diffusion can readily occur. A variety of electrochemical and spectroelectrochemical data are brought together to evaluate this model.;While the theoretical groundwork informs the synthetic chemist of the ideal intra- and intermolecular interactions an application requires, the ability to design molecules to meet these requirements proves challenging. Nevertheless, this dissertation illustrates several design strategies as well as several readily accessible means to experimentally evaluate the intra- and intermolecular interactions present in our systems. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html).