Self-assembly of electron-rich and electron-poor naphthalene rings
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Molecular self-assembly through non-covalent interactions is an integral part of countless natural and synthetic materials. The Iverson group specifically focuses on aromatic donor-acceptor interactions and the subsequent self-assembly of molecules containing these functionalities. The work has predominately utilized association between the electron-rich 1,5-dialkoxynaphthalene (DAN) and the electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) to create numerous self-assembled structures through intramolecular or intermolecular aromatic donor-acceptor interactions. The self-assembly and inherent electronic properties of aromatic units have made them attractive candidates for nature-inspired molecules, molecular machines and organic electronic materials. The focus of these D-A interactions now shifts from an aqueous environment as solid state aromatic D-A interactions are promising modes of driven self-assembly for molecular architectures geared towards material applications. Aromatic units have long been applied in areas such as organic electronic materials due to their inherent charge transport properties. NDI has become a molecule of considerable interest among the organic electronics community due its electron transporting properties and ability to self-assemble. Therefore a thorough understanding of NDI and DAN-NDI self-assembly in the solid state should be of importance for the improvement and development of molecular architectures for organic electronic devices. The following dissertation chapters focus on NDI or its aromatic D-Acomplex with DAN. Chapter 2 investigates an unusual thermochromic behavior that occurred in our previous study when several solid state DAN:NDI mixtures lost their characteristic red color while crystallizing from the mesophase. Chapter 3 describes the synthetic progress towards a rigid, non-conjugated DAN-NDI molecule that retains electrostatic complementarity and ultimately led us to explore solid state non-covalent interactions of conjugated aromatic NDI-donor polymers. Chapter 5 describes an approach to synthesize conjugated NDI polymers and a diyne NDI to serve as an important synthetic intermediate. The work in chapter 6 tests the solid state association between neutral aromatic donor and acceptor polymer strands. The work enhances the present understanding of these D-A interactions in different phases. The results also support recent discussions about aromatic stacking dominated by interactions between highly polarized groups on the periphery of aromatic units rather than overall polarization of the aromatic ring itself (i.e. D-A interactions).