Elucidating the reactivity and structure-property relationships of benzobisoxazoles for the rational design of conjugated materials
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Benzobisoxazoles are rigid electron deficient aromatic heterocycles with good thermal, environmental, and chemical stability. Much work has been done on the design of new electron rich conjugated materials for organic semiconductors, however, the research on modification or development of electron deficient aromatics has been limited. Our group has developed a mild synthesis of non-halogenated and 4,8-dihalogenated benzobisoxazoles from cheap and readily available starting materials to use as electron deficient moieties in organic semiconductors. Using the halogens as synthetic handles to further functionalize the benzobisoxazoles, the optical, electronic, and physical properties of the system are tuned through inductive, resonance, and/or cross-conjugation effects. Likewise, the halogens can be utilized for direct polymerization through the 4,8-axis which creates polymers with much different properties than those synthesized through the traditional 2,6-axis. These new benzobisoxazoles can be polymerized or functionalized with ease at either axis producing materials with a wide-range of properties from wide band gap, highly fluorescent materials for blue organic light emitting diodes to narrow band gap, broad absorbing materials for organic photovoltaics. In order to expedite the search for new materials, we have used Density functional tTheory (DFT) and time-dependent DFT (TDDFT) to model properties and focus our efforts on the structures with the most desirable properties. This has led us to develop and investigate the properties of a diverse set of benzobisoxazole materials which can be efficiently prepared from common synthetic intermediates for organic semiconducting applications.