In situ formation of N-heterocyclic carbene-bound single-molecule junctions

0492829 - FZÚ 2019 RIV US eng J - Journal Article
Doud, E.A. - Inkpen, M.S. - Lovat, G. - Montes Muñoz, Enrique - Paley, D.W. - Steigerwald, M.L. - Vázquez, Héctor - Venkataraman, L. - Roy, X.
In situ formation of N-heterocyclic carbene-bound single-molecule junctions.
Journal of the American Chemical Society. Roč. 140, č. 28 (2018), s. 8944-8949. ISSN 0002-7863. E-ISSN 1520-5126
R&D Projects: GA ČR GA15-19672S
Institutional support: RVO:68378271
Keywords : self-assembled monolayers * gold surfaces * conductance * chemisorption
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 14.695, year: 2018

Self-assembled monolayers (SAMs) formed using N-heterocyclic carbenes (NHCs) have recently emerged as thermally and chemically ultrastable alternatives to those formed from thiols. The rich chemistry and strong sigma-donating ability of NHCs offer unique prospects for applications in nanoelectronics, sensing, and electrochemistry. Although stable in SAMs, free carbenes are notoriously reactive, making their electronic characterization challenging. Here we report the first investigation of electron transport across single NHC-bound molecules using the scanning tunneling microscope-based break junction (STM-BJ) technique. We develop a series of air-stable metal NHC complexes that can be electrochemically reduced in situ to form NHC electrode contacts, enabling reliable single molecule conductance measurements of NHCs under ambient conditions. Using this approach, we show that the conductance of an NHC depends on the identity of the single metal atom to which it is coordinated in the junction. Our observations are supported by density functional theory (DFT) calculations, which also firmly establish the contributions of the NHC linker to the junction transport characteristics. Our work demonstrates a powerful method to probe electron transfer across NHC electrode interfaces, more generally, it opens the door to the exploitation of surface-bound NHCs in constructing novel, functionalized electrodes and/or nanoelectronic devices.
Permanent Link: http://hdl.handle.net/11104/0286260