Photophysical Characterization of Pyrylium Salts

Sophia Jaeger, Thomas Guarr

Pyrylium salts are cationic species distinguished by a trivalent oxygen within a six membered conjugated ring.  Pyryliums can be utilitzed as precursors for heterocyclic benzene analogs, photocatalysts, fluorescent cellular probes, organic light emitting diodes, and in photodynamic therapies.  Their photophysical characteristics lend them to these applications.  To better understand the impact of structure on the photophysical properites of pyryliums, ten unique pyrylium salts were synthesized from four synthetic pathways.  The resulting pyryliums were then characterized using NMR and mass spectrometry.  Once their structures were confirmed, their photophysical characteristics were examined via UV-Visible spectroscopy and fluorescence spectroscopy.  In comparing the structure and unique spectrum of each pyrylium the impact of substituents on the central pyrylium ring on the fluorescent wavelenegth and lifetime were examined.

Sophia was a pleasure to work with this summer!  She just graduated from Michigan Tech University and is returning in the fall for her MS.  She impressed us with her knowledge but mostly with her infectious “chemistry is fun” attitude!  Her project was kind of narrow, but her contributions to the lab this summer were outsized and her hard work provided a lot of valuable info.  Thanks for spending the summer with us!

Optimizing Solubility and Stability of 2,6-Diethyl-4-(4-Methoxyphenyl)pyridinium Compounds for Redox Flow Batteries

Margaret Cooper, Madison Shaffer, Thomas Guarr

As the demand for renewable energy grows, the need for long duration energy storage has become critical.  Redox flow batteries (RFBs) have emerged as a potential alternative for grid-scale energy storage as they are both safe and environmentally friendly.  RFBs employ two electrolyte solutions (an anolyte and catholyte) and achieving commercially viable energy density in such systems requires that the anolyte displays a low reduction potential and high solubility.  Previous research has shown that pyridinium compounds offer low reduction potentials, but varying solubilities and stability in their reduced states.  This work focuses on 2,6-diethyl-4-(4-methoxyphenyl)pyridinium compounds with various 1-aryl substituents in an attempt to improve solubility and stability while maintaining a low reduction potential.  These compounds are prepared via condensation of 2,6-diethyl-4-(4-methoxyphenyl)pyrylium with the desired aryl amine.  Solubilities were measured by UV-visible spectroscopy, while radical stability was measure by cyclic voltammetry.

Maggie attends Montana State University and we were lucky to have her join us at the OESLab in Holland this summer.  She is a lot of fun to have around and she is up for anything, including a lot of synthesis projects and analysis. Thanks for being a trooper!  Enjoy the rest of your summer and enjoy returning to Big Sky country!