Supramolecular Radical Electronics

Supramolecular radical chemistry is an emerging areabridging supramolecularchemistry and radical chemistry, and the integration of radicals intothe supramolecular architecture offers a new dimension for tuningtheir structures and functions. Although various efforts have beendevoted to the fabrication of supramolecular junctions, the chargetransport characterization through the supramolecular radicals remainedunexplored due to the challenges in creating supramolecular radicalsat the single-molecule level. Here, we demonstrate the fabricationand charge transport investigation of a supramolecular radical junctionusing the electrochemical scanning tunneling microscope-based breakjunction (EC-STM-BJ) technique. We found that the conductance of asupramolecular radical junction was more than 1 order of magnitudehigher than that of a supramolecular junction without a radical andeven higher than that of a fully conjugated oligophenylenediaminemolecule with a similar length. The combined experimental and theoreticalinvestigations revealed that the radical increased the binding energyand decreased the energy gap in the supramolecular radical junction,which leads to the near-resonant transport through the supramolecularradical. Our work demonstrated that the supramolecular radical canprovide not only strong binding but also efficient electrical couplingbetween building blocks, which provides new insights into supramolecularradical chemistry and new materials with supramolecular radicals.