Understanding the Role of Parallel Pathways via In‐Situ Switching of Quantum Interference in Molecular Tunneling Junctions. (3rd July 2020)

• Record Type: Journal Article
• Authors: Soni, Saurabh; Ye, Gang; Zheng, Jueting; Zhang, Yanxi; Asyuda, Andika; Zharnikov, Michael; Hong, Wenjing; Chiechi, Ryan C.
• Is Part Of: Angewandte Chemie. Volume 132:Number 34(2020)
• Page Start: 14414
• Page End: 14418
• Publication Date: 2020-07-03
• Subjects: EGaIn -- molecular electronics -- quantum interference -- self-assembled monolayers -- STM-BJ; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202005047
• Languages: English
• ISSNs: 0044-8249

Abstract

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. Abstract : Manipulating conductance in parallel molecular pathways is a crucial element in molecular electronics. We explore intramolecular parallel pathways with different bond topology, in form of a quantum circuit, in tunneling junctions comprising self‐assembled monolayers. We employ quantum‐interference switching/gating with an acid, without any structural changes, in single‐molecular junctions.