The Conductance of Porphyrin-Based Molecular Nanowires Increases 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, nonclassical behavior 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 highest occupied molecular orbital-lowest unoccupied molecular orbital gap. Our study reveals the potential of these molecular wires as interconnects in future molecular-scale circuitry.

Constitution and Conductivity of Metalloporphyrin Tapes

“…The excellent conductivity of the Zn(DMP) oCVD film (Figure ; Supporting Information, Figure S17) likely arises from the exclusive triple linkages in the porphyrin tapes,, , , the good polymerization yield (LDI‐HRMS, UV/Vis/NIR) and the absence of redox active metal centers and strongly bound axial ligands.…”

Turning the Tap: Conformational Control of Quantum Interference to Modulate Single‐Molecule Conductance

“…Measurements of the conductance of electrode j molecule j electrode junctions,interpreted with the aid of theoretical treatments and computational modeling,h ave given insight into the fundamentals of through-molecule electron transport, leading to the design of molecular wires, [1] molecular switches, [2] and molecular diodes. [3] One of the most interesting aspects of single-molecule electronics to emerge from these studies is the phenomenon of room-temperature quantum interference (QI).…”

A Single Atom Change Turns Insulating Saturated Wires into Molecular Conductors

“…indicating that our results can be explained, at least qualitatively, using this picture: changes in both 89 and can lower β, in accordance with findings by others. 10,30,31,32,33,34,35,36,37,38,39,40 This approach, however, does not capture the observed changes in the dielectric response of the junctions directly, and, of course, it does not explicitly account for the local changes in the electrostatic potential profile induced by X observed in the DFT calculations; these effects are essentially compensated by the large change in Γ of 3 orders of magnitude.…”

“…We note that the value of β also depends, besides the chemical nature of the molecular backbone, 2,5,15,16,17 on the molecule−electrode coupling strength Γ that is naturally related to 89 31, 33, 34 . For molecular wires, where 89 decreases with the number of repeat units due to an increase in conjugation with increasing molecular length, extremely low (<0.1 Å -1 ) 30,31,35,36 and even negative β values have been reported 35,37,38,39,40 . Such low β values are also a signature of incoherent hopping and these junctions, in particular those containing redox centres, may operate in this hopping regime (also called incoherent tunnelling regime).…”