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Correlation of breaking forces, conductances and geometries of molecular junctions.

Yoshida K, Pobelov IV, Manrique DZ, Pope T, Mészáros G, Gulcur M, Bryce MR, Lambert CJ, Wandlowski T - Sci Rep (2015)

Bottom Line: Correlations between forces, conductances and junction geometries demonstrate that aromatic tolanes bind between electrodes as single molecules or as weakly-conductive dimers held by mechanically-weak π - π stacking.In contrast with the other anchors that form only S-Au or N-Au bonds, the pyridyl ring also forms a highly-conductive cofacial link to the gold surface.Binding of multiple molecules creates junctions with higher conductances and mechanical strengths than the single-molecule ones.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.

ABSTRACT
Electrical and mechanical properties of elongated gold-molecule-gold junctions formed by tolane-type molecules with different anchoring groups (pyridyl, thiol, amine, nitrile and dihydrobenzothiophene) were studied in current-sensing force spectroscopy experiments and density functional simulations. Correlations between forces, conductances and junction geometries demonstrate that aromatic tolanes bind between electrodes as single molecules or as weakly-conductive dimers held by mechanically-weak π - π stacking. In contrast with the other anchors that form only S-Au or N-Au bonds, the pyridyl ring also forms a highly-conductive cofacial link to the gold surface. Binding of multiple molecules creates junctions with higher conductances and mechanical strengths than the single-molecule ones.

No MeSH data available.


Experimental breaking force Fb,e (circles, scale on the left) and its standard deviation (error bars) for molecular junctions formed by tolanes with different anchoring groups as a function of the logarithm of normalised junction conductances prior to the breaking event log(Gend/G0).The solid curves (scale on the right) represent the percentage of traces ϕ used to determine Fb,e at each value of Gend. The peaks of ϕ are attributed to the breaking of junctions with conductance in the indicated range. The sum values of ϕ are shown in the panel labels. The horizontal lines represent the mean values of the breaking forces Fb,e in the corresponding ranges of Gend (Table 1).
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f3: Experimental breaking force Fb,e (circles, scale on the left) and its standard deviation (error bars) for molecular junctions formed by tolanes with different anchoring groups as a function of the logarithm of normalised junction conductances prior to the breaking event log(Gend/G0).The solid curves (scale on the right) represent the percentage of traces ϕ used to determine Fb,e at each value of Gend. The peaks of ϕ are attributed to the breaking of junctions with conductance in the indicated range. The sum values of ϕ are shown in the panel labels. The horizontal lines represent the mean values of the breaking forces Fb,e in the corresponding ranges of Gend (Table 1).

Mentions: The mechanical properties of molecular junctions were characterised by determining their breaking forces Fb as a function of their conductance prior to the breaking Gend (Supplementary Note 3). We found that due to the stochastic variation of the junction's structure, different stages of the elongation process are better identified by Gend than by the extension length Δz. Figure 3 displays the experimental mean breaking force Fb,e as well as the percentage of analysed traces ϕ vs. log(Gend/G0) for all studied tolanes. ϕ equals the number of traces with given Gend divided by the total number of measured traces. Due to the different junction formation probability and a restriction to low-noise junctions, the highest percentage of traces was analysed for BT2 and PY2, the lowest for SH1, NH22 and CN2, and an intermediate one for SH2.


Correlation of breaking forces, conductances and geometries of molecular junctions.

Yoshida K, Pobelov IV, Manrique DZ, Pope T, Mészáros G, Gulcur M, Bryce MR, Lambert CJ, Wandlowski T - Sci Rep (2015)

Experimental breaking force Fb,e (circles, scale on the left) and its standard deviation (error bars) for molecular junctions formed by tolanes with different anchoring groups as a function of the logarithm of normalised junction conductances prior to the breaking event log(Gend/G0).The solid curves (scale on the right) represent the percentage of traces ϕ used to determine Fb,e at each value of Gend. The peaks of ϕ are attributed to the breaking of junctions with conductance in the indicated range. The sum values of ϕ are shown in the panel labels. The horizontal lines represent the mean values of the breaking forces Fb,e in the corresponding ranges of Gend (Table 1).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355744&req=5

f3: Experimental breaking force Fb,e (circles, scale on the left) and its standard deviation (error bars) for molecular junctions formed by tolanes with different anchoring groups as a function of the logarithm of normalised junction conductances prior to the breaking event log(Gend/G0).The solid curves (scale on the right) represent the percentage of traces ϕ used to determine Fb,e at each value of Gend. The peaks of ϕ are attributed to the breaking of junctions with conductance in the indicated range. The sum values of ϕ are shown in the panel labels. The horizontal lines represent the mean values of the breaking forces Fb,e in the corresponding ranges of Gend (Table 1).
Mentions: The mechanical properties of molecular junctions were characterised by determining their breaking forces Fb as a function of their conductance prior to the breaking Gend (Supplementary Note 3). We found that due to the stochastic variation of the junction's structure, different stages of the elongation process are better identified by Gend than by the extension length Δz. Figure 3 displays the experimental mean breaking force Fb,e as well as the percentage of analysed traces ϕ vs. log(Gend/G0) for all studied tolanes. ϕ equals the number of traces with given Gend divided by the total number of measured traces. Due to the different junction formation probability and a restriction to low-noise junctions, the highest percentage of traces was analysed for BT2 and PY2, the lowest for SH1, NH22 and CN2, and an intermediate one for SH2.

Bottom Line: Correlations between forces, conductances and junction geometries demonstrate that aromatic tolanes bind between electrodes as single molecules or as weakly-conductive dimers held by mechanically-weak π - π stacking.In contrast with the other anchors that form only S-Au or N-Au bonds, the pyridyl ring also forms a highly-conductive cofacial link to the gold surface.Binding of multiple molecules creates junctions with higher conductances and mechanical strengths than the single-molecule ones.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.

ABSTRACT
Electrical and mechanical properties of elongated gold-molecule-gold junctions formed by tolane-type molecules with different anchoring groups (pyridyl, thiol, amine, nitrile and dihydrobenzothiophene) were studied in current-sensing force spectroscopy experiments and density functional simulations. Correlations between forces, conductances and junction geometries demonstrate that aromatic tolanes bind between electrodes as single molecules or as weakly-conductive dimers held by mechanically-weak π - π stacking. In contrast with the other anchors that form only S-Au or N-Au bonds, the pyridyl ring also forms a highly-conductive cofacial link to the gold surface. Binding of multiple molecules creates junctions with higher conductances and mechanical strengths than the single-molecule ones.

No MeSH data available.