Constructing Dual-molecule Junctions to Probe Intermolecular Crosstalk.

Understanding and controlling charge transport across multiple parallel molecules is fundamental to the creation of innovative functional electronic components, as future molecular devices will likely be multi-molecular. The smallest possible molecular ensemble to address this challenge is a dual-molecule junction device, which has potential to unravel the effects of intermolecular crosstalk on electronic transport at the molecular level that cannot be elucidated using either conventional single-molecule or self-assembled monolayer (SAM) techniques. Herein, we demonstrate the fabrication of an STM dual-molecule junction device, which utilizes noncovalent interactions and allows for direct comparison to the conventional STM single-molecule device. STM-BJ measurements reveal a decrease in conductance of 10% per molecule from the dual-molecule to the single-molecule junction device. Quantum transport simulations indicate this decrease is attributable to intermolecular crosstalk (i.e. intermolecular π-π interactions), with possible contributions from substrate-mediated coupling (i.e. molecule-electrode). This study provides the first experimental evidence to interpret intermolecular crosstalk in electronic transport at the STM-BJ level, and translates the experimental observations into meaningful molecular information to enhance our fundamental knowledge of this subject matter. This approach is pertinent to the design and development of future multi-molecular electronic components, and also to other dual-molecular systems where such crosstalk is mediated by various noncovalent intermolecular interactions (e.g. electrostatic and hydrogen bonding).