Understanding Intermolecular Charge Transport in Cucurbit[8]uril Encapsulated Pyridinium Dimers

Device performance in organic electronics is intimately controlled by a balance between intramolecular and intermolecular charge transport. Despite recent progress in understanding intermolecular charge transport, it remains challenging to control the conformation and orientation of conjugated polymer backbones to maximize orbital overlap. In this talk, we introduce a new strategy for studying interchain charge transport at the single molecule level using pi-stacked junctions driven by host-guest complexation. Extensive chemical characterization demonstrates that homoternary complexes are formed between four types of pyridinium monomers and cucurbit[8]uril (CB[8]) in a head-to-tail structure with high affinity. Intermolecular charge transport through π-stacked dimers is directly studied using scanning tunneling microscope-break junction (STM-BJ) technique, revealing unexpectedly high conductance levels over long-distance transport pathways compared to isolated, single pyridinium junctions. Density functional theory simulations show planarized geometries and strong LUMO-LUMO coupling upon the formation of the supramolecular complex, thereby facilitating intermolecular charge transport. Overall, this work provides a new approach to understand and modulate intermolecular charge transport with well-defined pi-stacked pyridinium dimers encapsulated by a host cavity for functional molecular electronic devices.