Understanding the Role of Parallel Pathways via In‐Situ Switching of Quantum Interference in Molecular Tunneling Junctions

Abstract

This study describes the modulation of tunneling probabilities in molecular junctions by switching one of two parallel intramolecular pathways. A linearly conjugated molecular wire provides a rigid framework that allows a second, cross‐conjugated pathway to be effectively switched on and off by protonation, affecting the total conductance of the junction. This approach works because a traversing electron interacts with the entire quantum‐mechanical circuit simultaneously; Kirchhoff's rules do not apply. We confirm this concept by comparing the conductances of a series of compounds with single or parallel pathways in large‐area junctions using EGaIn contacts and single‐molecule break junctions using gold contacts. We affect switching selectively in one of two parallel pathways by converting a cross‐conjugated carbonyl carbon into a trivalent carbocation, which replaces destructive quantum interference with a symmetrical resonance, causing an increase in transmission in the bias window.

Printable logic circuits comprising self-assembled protein complexes

“…Fabrication of printable logic circuits. A useful feature of molecular electronics is the ability to integrate circuit elements into individual molecules 48,49 . But the correlation between orientation and function in SAMs of PSI and the ability to print EGaIn 50 create the possibility for integrated circuits composed entirely of PSI, i.e., multiple junctions wired together without any conventional circuit elements such as resistors or diodes.…”

Promotion and suppression of single-molecule conductance by quantum interference in macrocyclic circuits

“…Four methylene (-CH 2 -) linkers break the conjugation between the anchor and the backbone, in a manner that weakens the coupling between the two channels and preserves the intrinsic LUMO-dominated transport properties of each conducting channel. These experiments demonstrate that the tetracationic cyclophane platform enables the construction of different electronic components [41][42][43][44] -namely, conductors and insulators-based on only one molecular platform.…”

Achieving Multiple Quantum-Interfered States via Through-Space and Through-Bond Synergistic Effect in Foldamer-Based Single-Molecule Junctions

“…Considering the through-space CQI as "2" for effective transmission and DQI as "1" for ineffective transmission, while weak through-bond conjugation as "0" for negligible contribution and strong conjugation as "−1" for negative contribution in this system, the final outputs based on multiple synergy for f-34Th, f-34Fu, f-23Th, and f-23Fu are 2, 1, 1, and 0, respectively, achieving ternary logic circuits. Inspired by these four states with modulation of molecular design, further exploration on in situ modulation 8,47,54 of different pathways' synergy can realize the switching among multiple states. So, it is highly possible to construct single-molecule multivalued logic circuits, such as ternary or quaternary logic gates, 12,13 which could be the key for single-molecule electronics to outrange the traditional silicon-based circuits exploiting the multiplicity of charge transport.…”