Hemilabile Ligands as Mechanosensitive Electrode Contacts for Molecular Electronics

Abstract

Single-molecule junctions that are sensitive to compression or elongation are an emerging class of nanoelectromechanical systems (NEMS). Although the moleculeelectrode interface can be engineered to impart such functionality,m ost studies to date rely on poorly defined interactions. We focused on this issue by synthesizing molecular wires designed to have chemically defined hemilabile contacts based on (methylthio)thiophene moieties.W em easured their conductance as af unction of junction sizea nd observed conductance changes of up to two orders of magnitude as junctions were compressed and stretched.Localised interactions between weakly coordinating thienyl sulfurs and the electrodes are responsible for the observed effect and allowr eversible monodentateQbidentate contact transitions as the junction is modulated in size.W eobserved an up to % 100-fold sensitivity boost of the (methylthio)thiophene-terminated molecular wire compared with its non-hemilabile (methylthio)benzene counterpart and demonstrate ap reviously unexplored application of hemilabile ligands to molecular electronics.

Folding a Single-Molecule Junction

“…We can rule out any contributions from variations in the molecule−electrode interface as a mechanism for the observed switching phenomena, as we have already demonstrated that thioanisole contacts do not change binding configuration upon junction compression. 21 Similarly, we can discount an interpretation of our results based on the formation of shorter junctions through Au-carbonyl contacts, as no interactions between a (di)ketone and gold electrodes (e.g., in measurements of molecular wires containing fluorenones, 33 anthraquinones, 34 or diketopyrrolopyrroles 35 ) have been reported. To verify that a syn ⇌ anti conformation change is responsible for the observed mechanoresistive effects, we performed power spectral density (PSD) analysis 36 on the junctions in their relaxed and compressed state.…”

“…Stacks of phenyl rings and other simple heteroaromatics are able to act as efficient conductors in molecular junctions, , with charge transported through π–π interactions. − In the device proposed by Franco et al, these effects are incorporated into a single molecule, where conductance is predicted to drop by orders of magnitude as the stacking configuration is mechanically unfolded and charge is forced to flow through the saturated propyl chain. Such a device would represent a new class of molecular electronic components responsive to mechanical stimuli, complementing the existing range that exploits changes in the electrode-molecule interface, − stereoelectronic configuration switching, , and stretching-dependent quantum interference effects , as the molecular junction is compressed and relaxed.…”

Tuning the thermoelectrical properties of anthracene-based self-assembled monolayers

“…LUMOdominate transport was also predicted for the thioetherterminated molecules in ref. 41, and measured experimentally for the longest molecule in ref. 42 and for the thioetherterminated anthracene in ref.…”

Single Dynamic Covalent Bond Tailored Responsive Molecular Junctions

“…As shown in Figure 5, IND shows a higher transmission probability than E ‐PCIH in almost all the energy choices. Due to the uncertainty of the gold electrode's contact configuration and solution environment, as well as inherent limitations in DFT calculations, the calculated Fermi level often deviates from the experimental value [29] . However, since these molecules are neither oxidized nor reduced, the Fermi level lies between the HOMO and the LUMO.…”