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Tuning single-molecule conductance by controlled electric field-induced trans-to-cis isomerisation

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C. S. Quintans, Denis Andrienko, Katrin F. Domke, Daniel Aravena, Sangho Koo, Ismael Díez-Pérez, Albert C. Aragonès

Original languageEnglish
Article number3317
JournalApplied Sciences (Switzerland)
Volume11
Issue number8
DOIs
Published2 Apr 2021

Bibliographical note

Funding Information: Funding: I.D.-P. thanks the ERC (Fields4CAT-772391) for financial support. A.C.A. thanks European Union for a H2020-MSCA-IF-2018 Fellowship (TECh-MoDE). K.F.D. is grateful for generous funding through the “Plus 3” program of the Boehringer Ingelheim Foundation. S.K. appreciate National Research Foundation of Korea for a research grant (NRF-2020R1A2C1010724). D.A. thanks Powered@NLHPC; this research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors

Abstract

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reac-tions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans-isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

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