Robust organic radical molecular junctions using acetylene terminated groups for C-Au bond formation

Francesc Bejarano, Ignacio Jose Olavarria-Contreras, Andrea Droghetti, Ivan Rungger, Alexander Rudnev, Diego Gutiérrez, Marta Mas-Torrent, Jaume Veciana, Herre S. J. van der Zant, Concepció Rovira, Enrique Burzurí and Núria Crivillers

Organic paramagnetic and electroactive molecules are attracting interest as core components of molecular electronic and spintronic devices. Currently, further progress is hindered by the modest stability and reproducibility of the molecule/electrode contact. We report the synthesis of a persistent organic radical bearing one and two terminal alkyne groups to form Au-C σ bonds. The formation and stability of self-assembled monolayers and the electron transport through single-molecule junctions at room temperature have been studied. The combined analysis of both systems demonstrates that this linker forms a robust covalent bond with gold and a better-defined contact when compared to traditional sulfur-based linkers. Density functional theory and quantum transport calculations support the experimental observation highlighting a reduced variability of conductance values for the C-Au based junction. Our findings advance the quest for robustness and reproducibility of devices based on electroactive molecules.

DOI: 10.1021/jacs.7b10019
 J. Am. Chem. Soc., 2018140 (5), pp 1691–1696