Topological Control of Carbon Nanohoops for Boosted Long-Range Coherent Transport.

Molecular topology offers a powerful yet underexplored strategy for controlling charge transport in molecular electronics. Here, we construct double-loop single-molecule junctions based on conjoined carbon bisnanohoops containing more than 15 phenylene units. Intrinsic curvature asymmetry between the two loops directs Au-π binding and enables controlled formation of distinct single-loop and double-loop transport configurations. The double-loop topology results in higher conductance and a substantially reduced attenuation factor compared with size-matched linear and single-loop analogues, allowing coherent tunneling to be sustained over transport lengths of up to ten phenylene units. Density functional theory calculations attribute this behavior to enhanced orbital coupling across phenylene units and improved electrode coupling arising from the double-loop connectivity. These results establish molecular topology as an effective design parameter for engineering long-range charge transport in π-conjugated systems.