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

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.