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

Saurabh Soni, Gang Ye, Jueting Zheng, Yanxi Zhang, Andika Asyuda, Michael Zharnikov, Wenjing Hong, Ryan C. Chiechi*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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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.
Original languageEnglish
Pages (from-to)14308-14312
JournalAngewandte Chemie (international edition)
Issue number34
Publication statusPublished - 17 Aug 2020
Externally publishedYes


  • EGaIn
  • molecular electronics
  • quantum interference
  • self-assembled monolayers
  • STM-BJ

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