Scanning tunneling microscope-break junction (STM-BJ) technique has been widely used to investigate electron transport across single molecule junctions. Although the focus is often on creating miniaturized versions of common electronic components such as transistors, or switches, the development of molecules that are highly insulating at the nanometer or sub-nanometer scale is also critically important. Past work has demonstrated that the single-molecule conductance of silane derivatives can be suppressed due to destructive quantum interference. However, designing and measuring highly insulating sub-nanometer molecules is difficult because tunneling conductance increases exponentially with decreasing molecular length. Short insulating molecules that can further scale down the dimensions of the junction have therefore not been widely explored. Here, we present a new series of small molecules where conductance is suppressed through a destructive quantum interference effect. Using the STM-BJ technique, we confirm that their single-molecule junction conductance is lower than analogous alkanes of similar length verifying their ability to function as insulators. Through density functional theory calculations, we rationalize the suppression of conductance in the junctions charting a pathway for chemical design of short insulating organic molecules.

Short organic molecular insulator based on destructive quantum interference

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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