Synthesis and Self-Assembly of New Polycyclic Aromatic Hydrocarbons

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Materials based on conjugated aromatic compounds show potential for the next generation of organic electronic devices, including displays and solar cells. Design of these materials requires the ability to tune molecular properties, as well as the ability to control how molecules are organized and positioned in media such as crystalline solids or liquid crystals. The proposed research uses synthetic organic chemistry to prepare new polycyclic aromatic compounds that are designed to self-assemble in predictable ways and aims to understand how molecular structure affects this self-assembly. Ultimately, this research program will provide insight to guide the design of new functional materials. Over the next five years, the research program will focus on three main areas: (i) Disk-shaped molecules composed of polycyclic aromatic hydrocarbons (PAHs) and peripheral flexible alkyl side chains can form columnar liquid crystal phases. Our studies have examined how modifications to molecular structure affect liquid crystalline properties. Based on our previous work, we will design new columnar liquid crystalline molecules based on electron-deficient PAHs and large disk-shaped molecules to probe the effect of structural modifications on liquid crystalline properties. In addition, we will prepare compounds can serve as molecular building blocks for the construction of extended, covalently linked frameworks. (ii) In contrast to the planar disk-shaped molecules described above, non-planar aromatic compounds often do not stack as effectively and engage in intermolecular interactions with other types of molecules, including fullerenes or carbon nanotubes. We will prepare new non-planar aromatic compounds and explore their ability to bind small molecules such as electron-deficient aromatic compounds and fullerenes. For example, we will prepare extended versions of tetraphenylenes with larger polycyclic aromatic units, forming compounds with a distinct cavity that is capable of binding other molecules, such as small aromatic compounds like TNT and fullerenes. (iii) We have shown that new luminescent liquid crystalline compounds can be prepared by nucleophilic aromatic substitution reactions of tetrafluoroterephthalonitrile with catechol derivatives. We have extended this methodology to incorporate other heteroatoms in these polycyclic systems and have demonstrated that heteroatom substitution has a dramatic impact on solid state organization and luminescence. Using our methodology, we will focus on the preparation of functional materials such as electron accepting materials for organic electronics. We will also use this approach to prepare more complex architectures where awkward molecular shape prevents effecting packing. These materials may serve as porous molecular solids for the encapsulation of small molecules, gas storage, or catalysis.