Bistable Conductance of Single C₆₀ Molecules in Solution Correlated With Molecular Orientation

Probing charge transport through individual molecules in solution remains challenging due to the structural variations of electrodes and associated noise. Here, we use gold sub-nm gap electrodes to investigate electron transport through individual C₆₀ molecules in toluene. Under a constant bias of 50 mV, the devices remain stable for over one hour and reveal frequent switching between two discrete conductance states. Statistical analysis combined with first-principles transport calculations suggests that the observed conductance states are consistent with distinct molecule-electrode coupling geometries associated with different molecular orientations. The higher-conductance state is associated with a hexagonal facet facing the electrode, whereas the lower-conductance state corresponds to a C-C bond between adjacent hexagons pointing toward the electrode. These results demonstrate real-time monitoring of orientation-dependent single-molecule transport in solution and highlight molecular orientation as a key factor governing electron transmission.