Research Symposium

BIO

My name is Kiera Powers, a second year at FSU from Sarasota, Florida, working toward a bachelor’s degree in chemistry. Following the completion of my undergraduate studies, I aim to obtain a PhD in chemistry and hope to establish a career specializing in either Nuclear or Materials chemistry.

Spin Density Distribution in Organic Biradicals

Abstract

Organic biradicals are molecules with two unpaired electrons. Researchers use molecules like these for spin polarization transfer, a technique that lines up all electrons in a molecule in one direction. Molecules with similar properties are used in magnetic resonance imaging, quantum sensing, and as catalysts. The organic biradicals in this study are very large, made of hundreds of atoms. As a result, their electron paramagnetic resonance (EPR) spectra are very forested, with complicated hyperfine splitting patterns that make them difficult to analyze. Our goal is to reproduce their spectra through simulation. The three molecules analyzed in this study differ only by their carbon-carbon bridge connecting the two radicals. The first molecule has a bridge consisting of a carbon triple bond; the second contains a bridge double the length, with two carbon-carbon triple bonds; the third has no bridge, and the two radicals are connected with aromatic rings. The purpose of this study is to find the hyperfine couplings in order to understand the spin systems of each molecule and the differences between them. To this aim, we used quantum chemistry calculations to compute the molecular and electronic structure, estimate the electron-nuclear hyperfine coupling, and simulate the EPR spectrum. Our simulations do not fully reproduce the experimental results, meaning that the exact spin systems of these molecules remain difficult to reproduce with the current computational tools.

Keywords: Chemistry, EPR, Spin, Organic Radical, Hyperfine, Magnetic Resonance