Length and temperature dependent conduction of ruthenium-containing redox-active molecular wires

Liang Luo, Ahmed Benameur, Pierre Brignou, Seong Ho Choi, Stéphane Rigaut, C. Daniel Frisbie

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We report the electrical transport characteristics of two series of linear ruthenium(II) bis(δ-arylacetylide) molecular wires, RunM and RunH (n = 1, 2, 3), consisting of multiple redox-active Ru(II) centers and different saturated side chains (M = -CH2-, and H = -O(CH2)6-) with lengths up to 6.0 nm. The self-assembled monolayers of these molecular wires on Au surfaces were comprehensively characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RA-FTIR), and cyclic voltammetry. The resistance and current (I)-voltage (V) characteristics of these molecular wires were measured as a function of length and temperature using conducting probe atomic force microscopy (CP-AFM). Both series of molecular wires exhibited very weak length dependence of the wire resistance, the β value of Ru nM being 1.02 nm-1, and that of RunH being 1.64 nm-1, indicating a high degree of electronic coupling between the redox centers. Further analysis of I-V characteristics revealed that the charge transport in RunM junctions was direct tunneling, but in Ru nH (n = 2, 3) junctions with the long chains the mechanism was thermally activated hopping, consistent with the temperature-dependent conduction measurement.

Original languageEnglish (US)
Pages (from-to)19955-19961
Number of pages7
JournalJournal of Physical Chemistry C
Issue number40
StatePublished - Oct 13 2011

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