Correlation of breaking forces, conductances and geometries of molecular junctions

Yoshida, Koji and Pobelov, Ilya V. and Manrique, David Zsolt and Pope, Tom and Meszaros, Gabor and Gulcur, Murat and Bryce, Martin R. and Lambert, Colin J. and Wandlowski, Thomas (2015) Correlation of breaking forces, conductances and geometries of molecular junctions. Scientific Reports, 5: 9002. ISSN 2045-2322

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 pi - pi 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.