Research ArticleCHEMICAL PHYSICS

A reversible single-molecule switch based on activated antiaromaticity

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Science Advances  27 Oct 2017:
Vol. 3, no. 10, eaao2615
DOI: 10.1126/sciadv.aao2615
  • Fig. 1 Model of the electrochemically activated BTP switch.

    BTP shows the neutral, low-conductance state. Upon oxidation, BTP gains antiaromatic character to the 6-4-6-π electron state that exhibits high conductance.

  • Fig. 2 STM-BJ measurements and electrochemical characterizations of TBTP.

    (A) A schematic diagram of a single Au-TBTP-Au junction. (B) Cyclic voltammogram of TBTP in dichloromethane solution (1 mM) with Bu4NPF6 (0.1 M) as the supporting electrolyte. Scan rate used is 100 mV/s. (C) Steady-state linear absorption spectroscopy of the neutral TBTP (orange) and the dication (green) obtained at a potential of 0.9 V (versus ferrocene [Fc+/0]). a.u., absorbance units. (D) Logarithm-binned 1D histograms (100 bins/decade) for TBTP in PC with tetrabutylammonium perchlorate at a tip bias of 0.09, 0.45, and −0.45 V (tip relative to the substrate). Inset: Peak conductance value versus applied tip bias.

  • Fig. 3 STM-BJ results showing the reversible single-molecule switch.

    (A) Logarithm-binned 1D histograms for TBTP in PC with tetrabutylammonium perchlorate as the supporting electrolyte at a gate voltage (VG) of +2, −0.5, −1.4, and −1.5 V. The gate voltage is applied relative to the substrate. Inset: Peak conductance value versus applied gate voltage. (B) Cyclic on/off conductance values determined by switching between the positive gate voltage and negative gate voltage chosen to be beyond the oxidation/reduction thresholds. Error bars correspond to the full width at half maximum of the conductance histogram peaks. (C and D) 2D conductance-displacement histogram for TBTP at off state (VG = 0 V) (C) and on state (VG = −1.5 V) (D). Note that the bias applied across the molecular junction is fixed at 25 mV (tip relative to the substrate) during these measurements.

  • Fig. 4 DFT-based transmission calculations.

    (A) The molecular junction containing the neutral TBTP molecule (H, light pink; C, brown; and S, yellow) and eight fluorine atoms at about 1 Å above (dark blue) and below (light blue) the central rings to model the TBTP molecule in a +2 oxidized state. (B) Transmission as a function of energy for the neutral (orange) and the oxidized molecule (green). EF is the Fermi level of the junction.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/10/eaao2615/DC1

    Synthetic details

    DFT-optimized coordinates

    NMR and mass spectroscopy data

    fig. S1. UV-vis spectrum of TBTP.

    fig. S2. Steady-state linear absorption spectroscopy of TBTP obtained in a spectroelectrochemical setup.

    fig. S3. Steady-state linear absorption spectroscopy of TBTP and chemically oxidized TBTP dication.

    fig. S4. 1H NMR of the neutral TBTP and dication obtained by chemical oxidation.

    fig. S5. STM-BJ measurements of TBTP.

    fig. S6. STM-BJ measurements of a reversible single-molecule switch and in situ LSV.

    fig. S7. Transmission calculations for the neutral TBTP molecule using standard DFT methods and with DFT + Σ.

    table S1. DFT calculation (GIAO-B3LYP/6-31G**) of 1H NMR of TBTP and TBTP2+.

    table S2. DFT-based NICS calculations of the aromaticity of rings.

  • Supplementary Materials

    This PDF file includes:

    • Synthetic details
    • DFT-optimized coordinates
    • NMR and mass spectroscopy data
    • fig. S1. UV-vis spectrum of TBTP.
    • fig. S2. Steady-state linear absorption spectroscopy of TBTP obtained in a spectroelectrochemical setup.
    • fig. S3. Steady-state linear absorption spectroscopy of TBTP and chemically oxidized TBTP dication.
    • fig. S4. 1H NMR of the neutral TBTP and dication obtained by chemical oxidation.
    • fig. S5. STM-BJ measurements of TBTP.
    • fig. S6. STM-BJ measurements of a reversible single-molecule switch and in situ LSV.
    • fig. S7. Transmission calculations for the neutral TBTP molecule using standard DFT methods and with DFT + Σ.
    • table S1. DFT calculation (GIAO-B3LYP/6-31G**) of 1H NMR of TBTP and TBTP2+.
    • table S2. DFT-based NICS calculations of the aromaticity of rings.

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