Orthogonal Structural Design for Regulating Molecule-Electrode Coupling Strength.

Abstract

Modulating molecule-electrode coupling strength is crucial for optimizing molecular device performance, yet achieving precise and efficient control through molecular structural design remains challenging. Here, we orthogonally incorporate pyridine (P) and methylthio (S) anchoring groups into varied electron-deficiency cores, including benzene (B), benzothiadiazole (BT), and benzobisthiadiazole (BBT), and investigate six derivatives using the scanning tunneling microscope break junction (STM-BJ) technique. With increasing electron deficiency of the molecular core, theoretical calculations reveal a substantially larger improvement in energy-level alignment for methylthio than pyridine derivatives, yet this advantage is largely offset by the more pronounced reduction in molecule-electrode coupling for methylthio-terminated junctions, resulting in comparable conductance enhancement for both anchoring groups. For a given molecular core, stronger molecule-electrode coupling in methylthio derivatives promotes charge transport, resulting in higher conductance than pyridine derivatives. This orthogonal design strategy provides a general route for precise and efficient tuning of molecule-electrode interactions.