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    Single molecule vs. large area design of molecular electronic devices incorporating an efficient 2-aminepyridine double anchoring group

    Year: 2019

    Journal: Nanoscale, Volume 11, 1-Sep, page 15871–15880

    Authors: Herrer, L.; Ismael, A.; Martin, S.; Milan, D. C.; Serrano, J. L.; Nichols, R. J.; Lambert, C.; Cea, P.

    Organizations: fondos FEDEREuropean Union (EU) [MAT2016-78257-R, CTQ2015-70174-P, PGC2018-097583-B-I00]; project Hierarchical Self Assembly of Polymeric Soft Systems, "SASSYPOL", from the 7th Framework Programme(CEE) [Ref-607602]; DGA/Fondos FEDER (construyendo Europa desde Aragon) [E31_17R, E47_17R]; EPSRCEngineering & Physical Sciences Research Council (EPSRC) [EP/M029522/1, EP/M005046/1, EP/K007785/1]; UK EPSRCEngineering & Physical Sciences Research Council (EPSRC) [EP/M014452/1, EP/P027156/1, EP/N03337X/1]; European CommissionEuropean Commission Joint Research Centre [767187 - QuIET]; EUEuropean Union (EU); Tikrit University (Iraq); Iraqi Ministry of Higher Education [SL-20]; Ministerio de Economia y Competitividad from Spain

    When a molecule is bound to external electrodes by terminal anchor groups, the latter are of paramount importance in determining the electrical conductance of the resulting molecular junction. Here we explore the electrical properties of a molecule with bidentate anchor groups, namely 4,4 '-(1,4-phenylenebis(ethyne-2,1-diyl))bis(pyridin-2-amine), in both large area devices and at the single molecule level. We find an electrical conductance of 0.6 x 10(-4)G(0) and 1.2 x 10(-4)G(0) for the monolayer and for the single molecule, respectively. These values are approximately one order of magnitude higher than those reported for monodentate materials having the same molecular skeleton. A combination of theory and experiments is employed to understand the conductance of monolayer and single molecule electrical junctions featuring this new multidentate anchor group. Our results demonstrate that the molecule has a tilt angle of 30 degrees with respect to the normal to the surface in the monolayer, while the break-off length in the single molecule junction occurs for molecules having a tilt angle estimated as 40 degrees, which would account for the difference in their conductance values per molecule. The bidentate 2-aminepyridine anchor is of general interest as a contact group, since this terminal functionalized aromatic ring favours binding of the adsorbate to the metal contact resulting in enhanced conductance values.
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