The development of energy storage systems for next generation batteries has attracted substantial scientific attention. A major challenge lies in the design of new molecular architectures based on redox-active materials with improved electrochemical properties to boost storage capacity and performance. Recent work has largely focused on bulk electrochemical methods for characterizing the behavior of redox-active materials. Despite recent progress, however, we still lack a fundamental understanding of the charge transport properties of redoxmers at the molecular scale. In this work, we investigate the charge transport properties of two redox-active systems including pyridinium-based and nitroxide (TEMPO)-based molecules. To this end, we developed and used an electrochemical scanning tunneling microscope-break junction (ESTM-BJ) instrument that enables the direct measurement of molecular conductance as a function of the external gate voltage and chemical identity of the redox-active species. In the case of pyridinium-based molecules, we found that charge transport occurred over shorter molecular junction lengths due to intermolecular charge interactions upon increasing electrolyte concentration. Interestingly, charge transport in pyridinium-based molecular junctions can be tuned by formation of host-guest complexes with crown ethers, which presents intriguing new avenues for intermolecular complexation for controlling electronic properties. In the case of TEMPO-based molecules, we observed high levels of molecular conductance for TEMPO-containing oligomers compared to non-redox-active control molecules. Moreover, the conductance of redox-active molecules can be further tuned by altering redox states via electrochemical gating. Broadly, our results highlight the use of single molecule technique to characterize the charge transport properties of redox-active molecules. Overall, our work provides new information regarding the effect of intermolecular interactions on charge transport, which may aid in the design of new electrolytes for redox flow batteries with tunable molecular properties and/or new materials for smart nanoelectronics.

Single molecule charge transport in pyridinium and TEMPO-based redox-active molecules

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.