Additive Electron Pathway and Nonadditive Molecular Conductance by Using a Multipodal Bridging Compound

Abstract

We designed and synthesized a new quadrivial anchoring unit 4-TEB, to construct a stable single-molecule junction with gold electrodes, which should have equivalent conducting electron pathways between two electrodes. The conductances of single-molecule junctions comprising 4-TEB and its bidirectional counterpart 2-TEB were determined to be 2.7 × 10 −4 G 0 (2e 2 /h) and 5.0 × 10 −5 G 0 , respectively, by using scanning tunneling microscope break junction (STM-BJ) techniques. The single 4-TEB molecule junction had higher stability and conductivity compared to those of the single 2-TEB molecule junction. Although the number of electron pathways from/to the electrode to/from the molecule was additive using the equivalent multianchoring, the conductance of the singlemolecule junction was not additive. From first-principles electronic transport calculations, the mechanism for the new quadrivial 4-TEB single-molecule junction involved an overlap resonance effect to the HOMO conducting orbital, giving rise to tunneling. Using fixed nanogap electrodes, we constructed stable molecular junctions of 4-TEB and observed symmetric peaks in the derivative of the conductance−voltage (G−V) curves, which were assigned to electron transport through the HOMO on the basis of theoretical calculations.

Quantum interference in polyenes

“…S10 in the supplementary material, 37 we compare in detail our model transmissions ( Fig. 7) with the DFT transmission calculations of Kiguchi et al 70 There is rough agreement, but a direct comparison cannot be made as the two calculations use different anchoring groups to the electrodes.…”

“…There is a good reason why we turned to benzene -remarkably this multiprobe attachment system has been studied experimentally! Kiguchi and his co-workers 70 measured the conductance of a single-molecule junction with multipodal anchoring units, where multiple equivalent conduction pathways between two electrodes are formed. They synthesized 1,2,4,5-tetrakis (2-mercaptothienylethynyl) benzene derivative 4-TEB (see Scheme 8(a)) and its bidirectional counterpart 2-TEB (see Scheme 8(b)) and performed conductance measurements using the STM break junction technique.…”

Exploiting the interplay of quantum interference and backbone rigidity on electronic transport in peptides: a step towards bio-inspired quantum interferometers

“…28,29 Thus these effects must be taken into account in order to investigate the possibility of an interplay between quantum interference and vibrational fluctuations (backbone rigidity) in single peptide circuits.…”

Short-lived electron transfer in donor-bridge-acceptor systems

“…7a are , an effect previously found in conductance experiments [41,44]. One study found that electronic effects (functional groups) do not greatly modify single-molecule conductance [45] while geometrical (conformation) effects do have some effect [46].…”