Mechanics and Chemistry: Single Molecule Bond Rupture Forces Correlate with Molecular Backbone Structure

• Published in: Nano letters 2011-04, Vol.11 (4), p.1518-1523
• Main Authors: Frei, Michael, Aradhya, Sriharsha V, Koentopp, Max, Hybertsen, Mark S, Venkataraman, L
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Elastic Modulus; Electric Conductivity; Electron states; Exact sciences and technology; Gold - chemistry; Hardness; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials Testing; Mechanical and acoustical properties of condensed matter; Mechanical properties of nanoscale materials; Methods of electronic structure calculations; Nanostructures - chemistry; Nanostructures - ultrastructure; Particle Size; Physics; Stress, Mechanical; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl1042903

We simultaneously measure conductance and force across nanoscale junctions. A new, two-dimensional histogram technique is introduced to statistically extract bond rupture forces from a large data set of individual junction elongation traces. For the case of Au point contacts, we find a rupture force of 1.4 ± 0.2 nN, which is in good agreement with previous measurements. We then study systematic trends for single gold metal−molecule−metal junctions for a series of molecules terminated with amine and pyridine linkers. For all molecules studied, single molecule junctions rupture at the Au−N bond. Selective binding of the linker group allows us to correlate the N−Au bond-rupture force to the molecular backbone. We find that the rupture force ranges from 0.8 nN for 4,4′ bipyridine to 0.5 nN in 1,4 diaminobenzene. These experimental results are in excellent quantitative agreement with density functional theory based adiabatic molecular junction elongation and rupture calculations.