Functionalizing Polyaromatic Materials with Boranes and Borenium Ions

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Polycyclic aromatic hydrocarbons (PAHs) are large, planar molecules through which electrons can easily flow. They have found widespread use in organic electronics, as chemical sensors, in catalysis, and in bioimaging. In addition, some PAHs can provide an unusual type of oxygen, called singlet oxygen, for applications in photodynamic therapy, lithography, fluorescent anti-counterfeiting methodologies, and switches. The properties of PAHs can be manipulated by attaching various chemical groups to the periphery of these large molecules. The discovery of new groups for such attachment is important to improving the performance of PAHs in their many applications. Professor Frieder Jaekle, Chemistry Department, Rutgers University – Newark, is supported by the Chemical Synthesis Program to prepare PAHs that contain attached boron-nitrogen groups. The judicious choice of the site of the boron-nitrogen unit allows for the fine-tuning of electronic properties, which are utilized to maximize responses to physiological or environmental changes. These PAHs are integrated into polymers to improve their durability and are developed for applications ranging from electronic components to molecular switches. Additionally, the project contributes to the training of a diverse group of students in an interdisciplinary research environment at the interface of organic, inorganic and materials chemistry. Dr. Jaekle will organize outreach programs that allow students and their teachers from local high schools to experience research first-hand and to lear about career opportunities in STEM fields. The research group recruits high school summer students through that ACS Project SEED which is aimed at supporting socio-economically disadvantaged students. In this project, polycyclic aromatic hydrocarbons and related pi-conjugated polyaromatic species are functionalized with B-N Lewis pairs for applications in areas ranging from organic electronics to molecular switches. One direction focuses on the site-specific introduction of functional handles that allow for the fine-tuning of the optoelectronic properties. Through the judicious choice of functionalization, the steric strain and the ensuing contortions are systematically varied. At the limits of distortion, closed and open structures may coexist, giving rise to stimuli-responsive properties. Borenium ion formation is exploited to generate highly electron-deficient charged systems that undergo reduction to extensively delocalized neutral species at moderate potentials. The integration of these functional PAHs into polymeric systems and their attachment to quantum dots is pursued. The research is complemented by efforts to encourage participation of students from underrepresented groups.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.