The conductance of porphyrin-based molecular nanowires increases with length

TL;DR

This study shows that fused-oligo-porphyrin nanowires can exhibit conductance that remains constant or increases with length at room temperature, due to quantum effects reducing the HOMO-LUMO gap, making them promising for molecular circuitry.

Contribution

It demonstrates that the conductance of fused-oligo-porphyrin nanowires can increase with length, a non-classical behavior influenced by electrode material and anchor groups.

Findings

Conductance can be length-independent or increase with length.

The negative attenuation depends on electrode material.

The behavior is due to decreasing HOMO-LUMO gap with length.

Abstract

High electrical conductance molecular nanowires are highly desirable components for future molecular-scale circuitry, but typically molecular wires act as tunnel barriers and their conductance decays exponentially with length. Here we demonstrate that the conductance of fused-oligo-porphyrin nanowires can be either length independent or increase with length at room temperature. We show that this negative attenuation is an intrinsic property of fused-oligo-porphyrin nanowires, but its manifestation depends on the electrode material or anchor groups. This highly-desirable, non-classical behaviour signals the quantum nature of transport through such wires. It arises, because with increasing length, the tendency for electrical conductance to decay is compensated by a decrease in their HOMO-LUMO gap. Our study reveals the potential of these molecular wires as interconnects in future molecular-scale circuitry.