Charge Transport and Conductance Switching of Redox-Active Azulene Derivatives

Florian Schwarz, Michael Koch, Georg Kastlunger, Heinz Berke*, Robert Stadler, Koushik Venkatesan, Emanuel Lörtscher

*Corresponding author for this work

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Azulene (Az) is a non-alternating, aromatic hydrocarbon composed of a five-membered, electron-rich and a seven-membered, electron-poor ring; an electron distribution that provides intrinsic redox activity. By varying the attachment points of the two electrode-bridging substituents to the Az center, the influence of the redox functionality on charge transport is evaluated. The conductance of the 1,3 Az derivative is at least one order of magnitude lower than those of the 2,6 Az and 4,7 Az derivatives, in agreement with density functional theory (DFT) calculations. In addition, only 1,3 Az exhibits pronounced nonlinear current–voltage characteristics with hysteresis, indicating a bias-dependent conductance switching. DFT identifies the LUMO to be nearest to the Fermi energy of the electrodes, but to be an active transport channel only in the case of the 2,6 and the 4,7 Az derivatives, whereas the 1,3 Az derivative uses the HOMO at low and the LUMO+1 at high bias. In return, the localized, weakly coupled LUMO of 1,3 Az creates a slow electron-hopping channel responsible for the voltage-induced switching due to the occupation of a single molecular orbital (MO).

Original languageEnglish
Pages (from-to)11781-11786
Number of pages6
JournalAngewandte Chemie - International Edition
Volume55
Issue number39
DOIs
Publication statusPublished - 19 Sep 2016
Externally publishedYes

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Keywords

  • azulene
  • charge transport
  • hopping
  • molecular switch
  • redox-activity

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