Nitrogen Centered Radicals

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Andrzej Rajca of the Department of Chemistry at University of Nebraska-Lincoln is developing novel organic radicals that are applicable to the development of new magnetic, electronic, and optical technology. The goal of this research is the design, synthesis, and characterization of high-spin radicals, possessing the unusual parallel electron spin alignment and/or embedded within chiral structures. Structures of these radicals are optimized to provide single-component materials with electrical conductivity, paramagnetic agents for dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy, as well as organic spin filters for spintronics. As the proposed research activities involve organic synthesis, diverse physical/materials characterization, and computations, they will provide an opportunity to gain a broad education for scientists at all levels. The design and synthesis of these unconventional radicals, that are evolving with increasing complexity and challenge, provide excellent platforms for creative thinking and problem-solving. The syntheses of the unconventional molecules are of noteworthy interest related to the unusual synthetic methodology. The proposed conducting ultra-robust high-spin radicals provide better insight into electron (or hole) transport in cross-conjugated pi-systems, which are commonly known to be detrimental to the conductivity. They will enhance our understanding of the impact of multiple singly-occupied near-degenerate bands and strong antiferromagnetic interactions between the high-spin molecules that facilitate the electron transport. The proposed magnetically and thermally robust high-spin diradical that is optimized for molecular fluorescence would provide the first example of fluorescent high-spin diradical with near 100% population of the triplet ground state at ambient conditions. Those high-spin diradicals that are optimized for high DNP enhancements could advance the DNP NMR spectroscopy and its applications. The proposed enantiomerically pure double helical high-spin diradical dications and triradical cations are intriguing novel molecules with thermal robustness, enantiomerically pure chiral pi-system, and strong paramagnetic properties. The strength of chiroptical properties of the proposed double helical high-spin diradical dication is comparable to those of [n]helicenes, and thus, the coexistence of chirality and strong paramagnetism may render unique chiromagnetic properties that provide a novel platform for the discovery of new organic magneto-optic materials and efficient organic spin filters for spintronics. 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.