Tuning intermolecular π–π stacking by isomeric engineering in single-molecule junctions

Abstract

A comprehensive understanding of intermolecular π–π stacking effects is vital for advancing novel materials in fields such as organic semiconductors and optoelectronic devices. In this study, we engineered a series of molecular wires composed of pyridine, thiazole, and thiophene units arranged in various configurations. Using the single-molecule scanning tunnelling microscopy-break junction (STM-BJ) technique, we investigated their charge transport properties and stacking effects. Through detailed single-molecule conductance measurements, flicker noise analysis, and current–voltage (I–V) studies, we demonstrated that the degree of intramolecular charge polarization was directly correlated with stacking capability. Additionally, by integrating theoretical analyses, we elucidated the mechanism for manipulating the intermolecular π–π stacking effect at the microscale. These insights establish a structure–property relationship between intramolecular charge polarization and intermolecular stacking-driven charge transport, providing a foundation for designing advanced materials based on tunable intermolecular interactions.