CAREER: Constructing Conjugated Heteroarene Architectures via Ring-Expansion Reactions with Anti-Aromatic Boroles

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Materials that emit light when electricity is passed through them have a myriad of applications including LED light bulbs, computer displays, and medical imaging devices. Conversely, materials that generate electricity when exposed to light are used in applications including solar energy conversion. While there are a number of materials that have these properties, there is a challenge in developing ones in which the light that is absorbed or emitted can be tuned to specific colors. Dr. Caleb Martin, Department of Chemistry and Biochemistry, Baylor University, is supported by the Chemical Synthesis Program of the Chemistsry Division, to prepare materials containing boron and phosphorus or sulfur that function as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). By varying the amounts of these elements the color of light that is emitted or absorbed can be selectively changed. These light emitting/absorbing units are incorporated into polymers to form flexible OLEDs and OPVs that can be used in a variety of applications. This project also contains outreach efforts through partnerships with non-profit organizations in Waco that serve low income and homeless students. Interactive activities are related to the project with the ultimate goal to help increase the post-secondary enrollment of low income underrepresented minorities pursuing studies in the STEM fields. The project's goals are to synthesize boron containing analogues of benzene and other extended aromatic compounds that feature boron and a lone pair containing heteroatom as valence isoelectronic substitutes for a C=C unit in the ring. The synthetic route involves a ring expansion methodology that takes advantage of the lability of the endocyclic boron-carbon bond in anti-aromatic borole reagents. The electronic properties of the boron containing heteroarenes are investigated computationally and spectroscopically with a focus on fluorescence and band gaps for application in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). Due to the accessibility of the borole reagents, the initial targets are monocyclic systems with per-aryl substitution. However, in order to decrease the HOMO-LUMO gap conjugation is being increased by forming polycyclic systems. Through partnerships with local non-profit organizations for low income and homeless students, interactive activities that are related to this project are being organized. The ultimate goal of this outreach is to help increase the post-secondary enrollment of low income underrepresented minorities pursuing studies in the STEM fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.