Topological insulator single molecule circuits formed with neutral organic radicals.

Incorporation of open-shell compounds into single molecule circuits can increase the scope of observable phenomena due to expanded electronic degrees of freedom in such molecules. For example, recent work has shown that organic diradical cations can exhibit orders of magnitude greater conductance than their neutral versions due to the topological edge states associated with radical pairs. Yet challenges and questions about how to create stable radical junctions and control their electronic properties still remain. Neutral diradicals which possess open-shell character but do not require oxidation are a promising class of molecules that have not been probed in molecular junctions in ambient conditions to date. Here, I will present our recent single molecule conductance measurements and electronic structure calculations on a class of such molecules in solution at room temperature on gold. We addapt the Su-Schrieffer-Heeger (SSH) model to our diradicals chemical structures and show good agreement with experimental results. Our work provides insights into molecular structures that promote radical character in molecular circuits, leading to higher conductance, and paves the way towards engineering single molecule junction properties.