Mechanical single-molecule potentiometers with large switching factors from ortho-pentaphenylene foldamers

Abstract

Molecular potentiometers that can indicate displacement-conductance relationship, and predict and control molecular conductance are of significant importance but rarely developed. Herein, single-molecule potentiometers are designed based on ortho-pentaphenylene. The ortho-pentaphenylene derivatives with anchoring groups adopt multiple folded conformers and undergo conformational interconversion in solutions. Solvent-sensitive multiple conductance originating from different conformers is recorded by scanning tunneling microscopy break junction technique. These pseudo-elastic folded molecules can be stretched and compressed by mechanical force along with a variable conductance by up to two orders of magnitude, providing an impressively higher switching factor (114) than the reported values (ca. 1~25). The multichannel conductance governed by through-space and through-bond conducting pathways is rationalized as the charge transport mechanism for the folded ortho-pentaphenylene derivatives. These findings shed light on exploring robust single-molecule potentiometers based on helical structures, and are conducive to fundamental understanding of charge transport in higher-order helical molecules.

Mechanically Induced Switching between Two Discrete Conductance States: A Potential Single-Molecule Variable Resistor

“…However, it remains a significant challenge to fabricate such solid-state single-molecule switches with high on–off conductance ratios that can complement or even extend the capabilities of conventional silicon-based technology for functions such as logic and memory . The on–off conductance switching ratios as high as 3 orders of magnitude have been predicted using molecular dynamics simulations, with typically much lower ratios (∼2–20) achieved experimentally. − However, a small number of experimental studies have realized single-molecule devices with relatively high on–off ratios, for instance, those induced by light (107) and mechanical means (114). The controlled modulation of electronic transport through a molecular junction can be achieved using a number of different techniques, including the regulation of temperature, pH, and light, and electrochemical or mechanical means.…”

Mechanical conductance tunability of a porphyrin–cyclophane single-molecule junction

“…Multiple oscillations in the conductance up to 1.5 orders of magnitude are visible during the breaking events, demonstrating the largest reported mechanosensitivity in the case of cyclophane-like systems. 23 Similar conductance variations in [2.2]paracyclophane single-molecule junctions have been attributed to a stick-slip motion between the anchoring group and the gold electrodes, which enables the molecule to get close to or even cross the DQI-related transmission dip several times in a single breaking event. 7 As shown in Fig.…”

“…Multiple oscillations in the conductance up to 1.5 orders of magnitude are visible during the breaking events, demonstrating the largest reported mechanosensitivity in the case of cyclophane-like systems. 23 Similar conductance variations in times in a single breaking event. 7 As shown in Fig.…”

Tetrathiafulvalenes as anchors for building highly conductive and mechanically tunable molecular junctions

“…Additionally, the orientation of the molecule might change during the piezo ramp. Previously, several mechanically controlled switches have been demonstrated in molecular systems with multiple binding sites 3 , 55 – 57 . Our findings reported here provide a new design for mechanical molecular switches building on strongly coupled systems.…”