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Single-molecule conductance of functionalized oligoynes: length dependence and junction evolution
Pavel Moreno-García1, Murat Gulcur, David Zsolt Manrique
1Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
Journal of the American Chemical Society
|July 24, 2013
Summary
Dihydrobenzo[b]thiophene (BT) anchors significantly enhance electrical conductance in oligoyne molecular wires, outperforming traditional groups. This study combines experiments and theory to optimize molecular electronics for future applications.
Area of Science:
- Molecular electronics
- Condensed matter physics
- Organic chemistry
Background:
- Investigating molecular wires is crucial for advancing nanoscale electronic devices.
- Understanding the influence of anchor groups on electrical conductance is key to designing efficient molecular junctions.
- Oligoynes offer a promising platform for molecular wires due to their tunable electronic properties.
Purpose of the Study:
- To experimentally and theoretically investigate the length and anchor group dependence of electrical conductance in oligoyne molecular wires.
- To compare the performance of dihydrobenzo[b]thiophene (BT) as an anchor group against traditional groups like cyano (CN), amino (NH2), thiol (SH), and 4-pyridyl (PY).
- To elucidate the relationship between molecular structure, anchoring, and charge transport properties in single-molecule junctions.
Main Methods:
- Synthesis and characterization of diaryloligoynes with varying numbers of triple bonds (n=1, 2, 4) and different anchor groups.
- Utilizing scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques to form and measure single-molecule junctions.
- Employing density functional theory (DFT)-based calculations to model conductance, binding energies, and sliding effects of anchor groups.
Main Results:
- Dihydrobenzo[b]thiophene (BT)-terminated oligoynes exhibited a 100% junction formation probability and the highest conductance values among the studied oligoynes.
- BT anchors significantly improved conductance compared to CN, NH2, SH, and PY anchors.
- Experimental attenuation constants (βH) ranged from 1.7 nm⁻¹ (CN) to 3.2 nm⁻¹ (SH), with BT showing superior performance.
- DFT calculations predicted high electrical conductance for BT-terminated oligoynes and revealed oscillations in conductance and binding energies due to anchor group sliding.
Conclusions:
- The dihydrobenzo[b]thiophene (BT) moiety represents a superior anchoring group for enhancing electrical conductance in oligoyne molecular wires.
- The findings provide critical insights into structure-property relationships for molecular electronics, guiding the design of more efficient molecular junctions.
- Combined experimental and theoretical approaches are effective in understanding and optimizing charge transport in single-molecule systems.
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