Interplay Between Antiaromaticity and Diradical Character: New Structures and New Directions

With the support of the Chemical Synthesis and Chemical Structure, Dynamics, and Mechanisms B Programs in the Division of Chemistry, Professor Michael Haley and his students in the Department of Chemistry & Biochemistry at the University of Oregon are preparing molecules containing expanded architectures to answer fundamental scientific questions as well as to explore their materials properties. A key goal is to develop simple synthetic methods for the assembly of these electron-accepting molecules. The Haley group examines the optical, electronic, and/or magnetic properties of all new molecular scaffolds with an emphasis upon utilization of these materials in optoelectronic devices such as organic field effect transistors (OFETs) and organic photovoltaics (OPVs). This project serves as an excellent training ground for graduate and undergraduate researchers in fundamental and applied chemical synthesis, with exposure to organic synthesis, computational chemistry and x-ray crystallography. The broader impacts of this program include industrial internships of graduate students at local and regional companies, the exchange of graduate students with those of foreign collaborators, the hosting of extended stays of visiting scientists including professors from primarily undergraduate institutions (PUIs), and continued substantial involvement of undergraduates in chemical research via programs that promote participation of members of groups underrepresented in STEM (science, technology, engineering and mathematics). Research on non-benzenoid molecules has experienced a resurgence as chemists have recognized their potential as organic semiconductors characterized by the relatively low energy of their molecular orbitals and the small energy gap between their highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively). This project sets out to continue these systematic studies by examining (1) new heterocycle-fused ‘push-pull’ derivatives, (2) asymmetrically substituted compounds, and (3) pi-expanded ‘tetraradicaloid’ molecules. Further efforts will expand into completely new research directions such as their use as (4) antiaromatic, redox-active ligands and (5) antiaromatic N-heterocyclic carbenes in organometallic complexes. The molecules developed in these studies present opportunities for practical applications, particularly in the area of nanotechnology and low-cost electronics. In the longer term, these studies are expected to lead to a deeper fundamental understanding of the relationship between electronic structure and molecular architecture. 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.