Open-Shell Molecules: A Radical Design for Organic Optoelectronic Materials

CBE Department Seminar
Mark Chen
Lehigh University
Online via WebEx:
Wed, January 19, 2022 at 9:30 AM
Due to COVID-19, no refreshments will be available for this lecture.

Open-shell molecules possess unpaired electron density (radical character), which makes them intriguing candidate materials for many optoelectronic applications. Air-stable structures have been reported, but most require lengthy synthetic sequences with limited generality. Our lab has developed a concise synthetic strategy to rapidly access a variety of bisphenalenyls from commercial starting materials. We used this method to synthesize a neutral biradicaloid, Ph2-s-IDPL, and several novel heteroatom-substituted, π-radical cations. One such molecule is O-substituted (Ph2-PCPL)(OTf), which displays electrostatically-enhanced, intermolecular covalent-bonding interactions that impart remarkable charge transport properties. Specifically, we have discovered soluble derivatives that, when mixed with polystyrenesulfonate (PSS), enable the formation of water-processable, n-type conductive organic films that demonstrate high optical transparency (>94% transmission), electrical conductivity (σrt < 117 S/cm), and electron mobility (μe < 322 cm2 V-1 s-1). In these composites, PSS not only serves as a counterion, but also promotes n-doping and solution-phase aggregation, which leads to molecular ordering in solid-state. We have also discovered a N-substituted, red emissive, π-radical cation [(Ph2-PQPL)(OTf)] that is structurally distinct from all other reports of luminescent radicals, and achieves rare antiambipolar charge transport in field-effect transistors. N-substituted bisphenalenyls also display self-sensitized and reversible reactivity with dioxygen, which shows potential for applications for oxygen sensors and antimicrobial coatings.


Photo of Dr. Chen

Mark Chen is an assistant professor in the Department of Chemistry at Lehigh University. He received his B.A. and Ph.D. in Chemistry from Harvard University with M.-Christina White developing catalytic C-H bond oxidation methodologies. As a Dreyfus postdoctoral fellow in the lab of Jean Fréchet at U. C. Berkeley, he led a team developing polymeric and molecular materials for organic electronic devices. Since coming to Lehigh University, the Chen Lab has investigated the synthesis of open-shell organic molecules and their application to optoelectronic materials and devices. Mark is the recipient of several awards, including a Kaufman Foundation New Investigator Award (2015) and NSF CAREER Award (2021).

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