This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
A new preprint design is coming!
We have improved readability, clarity, accessibility, and opportunities for engagement.
Physical Sciences - Article
License:
This work is licensed under a CC BY 4.0 License. Read Full License
The control of chemical reactivity at the single-molecule scale offers a unique opportunity for the design and fabrication of advanced nanodevices.1-3 As a prototypical reaction, tautomerization has been extensively explored as a promising tool for manipulating the single-molecule conductance of tetrapyrrole macrocycles absorbed on a surface.4-8 However, the resulting molecular devices were determined to undergo dynamic, spontaneous interconversions even under cryogenic conditions, so that control of tautomeric switching between well-defined and specific states remains challenging. Here, we report the design of a reversible single-molecule switch based on an enol-keto tautomerization reaction, which demonstrates controllable bistability and inhibits spontaneous interconversion even at room temperature. Such control is achieved by modulating the potential energy surface (PES) through a bias-triggered charge injection process. Our results reveal that the device operates through switching between two distinct redox-related PESs with opposite thermodynamic driving forces, i.e., one exhibits strong preference for the conducting enol form, while the other exhibits a preference for the insulating keto form. The described switching mechanism constitutes a promising approach to achieve robust switching devices at the single-molecule scale.
Keywords
nanodevices, tautomerization, switching mechanism, switching devices
Figure 1
Figure 2
Figure 3
Figure 4
There is NO Competing Interest.
This is a list of supplementary files associated with this preprint. Click to download.
- SupportingInformation.docx
Single-molecule switching via controlled tautomerization at room temperature
- FigS1.png
Extended Data Fig. 1 | 1D conductance histograms for the deuterated analogue A-d2. a, A-d2 is synthesized by adding NaOD into a CD3OD solution of A (1), which is further neutralized by DCl (2). b, 1D conductance histograms of A-d2 at different biases. The STM-BJ experiments are performed on the 0.1 mM solution of A-d2 in TCB under ambient conditions. c, Distribution probabilities of states 'L' and 'H' are plotted against different biases. The emergence of the 'H' peak in the conductance histograms is not altered for deuterated A-d2 compared to the regular A (cf. Fig. 2), indicating that proton tunnelling is not a significant factor in the tautomerization mechanism.
- floatimage6.jpeg
Extended Data Fig. 2 | 1D conductance histograms of the water control experiments. All STM-BJ experiments were performed on a 0.1 mM solution of A. a, The experiment was performed in a glovebox and a dry TCB solvent. b-e, The following STM-BJ experiments were performed in the corresponding solvents under the conditions shown above the 1D conductance histograms. The control experiments (b-e) were performed under ambient conditions. Since the emergence of the 'H' peak in the conductance histograms does not appear to be affected by the presence/absence of water, the participation of this compound in the tautomerization mechanism can be ruled out. TMB is the abbreviation for sym-trimethylbenzene.
- floatimage7.jpeg
Extended Data Fig. 3 | Two-dimensional conductance histograms of compound A at different biases. The stretching distances (Δz) are shown in the inset, and the Gaussian fitting determines the peak centers. There is a 0.50 nm snap-back distance after the breaking of the gold-gold contact. For example, the corrected stretching distance at a 0.2 V bias is 0.94 nm (0.44 + 0.50 nm).
- Onlinefloatimage8.Png
Extended Data Fig. 4 | 1D and 2D conductance histograms of B-OMe. All the STM-BJ experiments were performed on a 0.1 mM solution of B-OMe with the bias changed from 0.1 to 0.6 V.
- Onlinefloatimage9.Png
Extended Data Fig. 5 | 1D conductance histograms of A with bias switching between 0.1 and 0.6 V. Peak centers of the dominant conductance peaks are determined by the Gaussian fitting in the corresponding 1D conductance histograms. The error was defined as the standard deviation of the Gaussian fitting.
- Onlinefloatimage10.Png
Extended Data Fig. 6 | I-V characterization without both switching and nonswitching traces. a, The 2D I-V was constructed from 3234 traces. The yellow line was achieved by the Gaussian fitting in each row of bins. b, Transition voltage spectrum is constructed from the above-fitted line. The inset shows the fitted line on a linear scale.
- Onlinefloatimage11.Png
Extended Data Fig. 7 | 1H NMR (500 MHz, CDCl3) spectrum of compound A (upper panel) and A-d2 (lower panel).
- Onlinefloatimage12.Png
Extended Data Fig. 8 | Potential energy profiles associated with the direct tautomerization reaction for the uncharged species (1) and the positively charged species (2) in the case of FZ = -0.05 V/Å. Energies are denoted in kcal/mol.
- Onlinefloatimage13.Png
Extended Data Fig. 9 | Potential energy profiles associated with the rejected alternative H2O-assisted reaction mechanism for the uncharged species (1) in the cases of FZ = -0.05 V/Å (blue) and FZ = +0.05 V/Å (red). Energies are denoted in kcal/mol.
Loading...
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 21 Oct, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Learn more about our company.
A new preprint design is coming!
We have improved readability, clarity, accessibility, and opportunities for engagement.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Physical Sciences - Article
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 21 Oct, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
License:
This work is licensed under a CC BY 4.0 License. Read Full License
The control of chemical reactivity at the single-molecule scale offers a unique opportunity for the design and fabrication of advanced nanodevices.1-3 As a prototypical reaction, tautomerization has been extensively explored as a promising tool for manipulating the single-molecule conductance of tetrapyrrole macrocycles absorbed on a surface.4-8 However, the resulting molecular devices were determined to undergo dynamic, spontaneous interconversions even under cryogenic conditions, so that control of tautomeric switching between well-defined and specific states remains challenging. Here, we report the design of a reversible single-molecule switch based on an enol-keto tautomerization reaction, which demonstrates controllable bistability and inhibits spontaneous interconversion even at room temperature. Such control is achieved by modulating the potential energy surface (PES) through a bias-triggered charge injection process. Our results reveal that the device operates through switching between two distinct redox-related PESs with opposite thermodynamic driving forces, i.e., one exhibits strong preference for the conducting enol form, while the other exhibits a preference for the insulating keto form. The described switching mechanism constitutes a promising approach to achieve robust switching devices at the single-molecule scale.
Figure 1
Figure 2
Figure 3
Figure 4
There is NO Competing Interest.
This is a list of supplementary files associated with this preprint. Click to download.
- SupportingInformation.docx
Single-molecule switching via controlled tautomerization at room temperature
- FigS1.png
Extended Data Fig. 1 | 1D conductance histograms for the deuterated analogue A-d2. a, A-d2 is synthesized by adding NaOD into a CD3OD solution of A (1), which is further neutralized by DCl (2). b, 1D conductance histograms of A-d2 at different biases. The STM-BJ experiments are performed on the 0.1 mM solution of A-d2 in TCB under ambient conditions. c, Distribution probabilities of states 'L' and 'H' are plotted against different biases. The emergence of the 'H' peak in the conductance histograms is not altered for deuterated A-d2 compared to the regular A (cf. Fig. 2), indicating that proton tunnelling is not a significant factor in the tautomerization mechanism.
- floatimage6.jpeg
Extended Data Fig. 2 | 1D conductance histograms of the water control experiments. All STM-BJ experiments were performed on a 0.1 mM solution of A. a, The experiment was performed in a glovebox and a dry TCB solvent. b-e, The following STM-BJ experiments were performed in the corresponding solvents under the conditions shown above the 1D conductance histograms. The control experiments (b-e) were performed under ambient conditions. Since the emergence of the 'H' peak in the conductance histograms does not appear to be affected by the presence/absence of water, the participation of this compound in the tautomerization mechanism can be ruled out. TMB is the abbreviation for sym-trimethylbenzene.
- floatimage7.jpeg
Extended Data Fig. 3 | Two-dimensional conductance histograms of compound A at different biases. The stretching distances (Δz) are shown in the inset, and the Gaussian fitting determines the peak centers. There is a 0.50 nm snap-back distance after the breaking of the gold-gold contact. For example, the corrected stretching distance at a 0.2 V bias is 0.94 nm (0.44 + 0.50 nm).
- Onlinefloatimage8.Png
Extended Data Fig. 4 | 1D and 2D conductance histograms of B-OMe. All the STM-BJ experiments were performed on a 0.1 mM solution of B-OMe with the bias changed from 0.1 to 0.6 V.
- Onlinefloatimage9.Png
Extended Data Fig. 5 | 1D conductance histograms of A with bias switching between 0.1 and 0.6 V. Peak centers of the dominant conductance peaks are determined by the Gaussian fitting in the corresponding 1D conductance histograms. The error was defined as the standard deviation of the Gaussian fitting.
- Onlinefloatimage10.Png
Extended Data Fig. 6 | I-V characterization without both switching and nonswitching traces. a, The 2D I-V was constructed from 3234 traces. The yellow line was achieved by the Gaussian fitting in each row of bins. b, Transition voltage spectrum is constructed from the above-fitted line. The inset shows the fitted line on a linear scale.
- Onlinefloatimage11.Png
Extended Data Fig. 7 | 1H NMR (500 MHz, CDCl3) spectrum of compound A (upper panel) and A-d2 (lower panel).
- Onlinefloatimage12.Png
Extended Data Fig. 8 | Potential energy profiles associated with the direct tautomerization reaction for the uncharged species (1) and the positively charged species (2) in the case of FZ = -0.05 V/Å. Energies are denoted in kcal/mol.
- Onlinefloatimage13.Png
Extended Data Fig. 9 | Potential energy profiles associated with the rejected alternative H2O-assisted reaction mechanism for the uncharged species (1) in the cases of FZ = -0.05 V/Å (blue) and FZ = +0.05 V/Å (red). Energies are denoted in kcal/mol.
Loading...