Chappell, Sarah, Brooke, Carly, Nichols, Richard J ORCID: 0000-0002-1446-8275, Cook, Laurence J Kershaw, Halcrow, Malcolm, Ulstrup, Jens and Higgins, Simon J ORCID: 0000-0003-3518-9061
(2016)
Evidence for a hopping mechanism in metal| single molecule| metal junctions involving conjugated metal-terpyridyl complexes; potential-dependent conductances of complexes [M(pyterpy)<sub>2</sub>]<SUP>2+</SUP> (M = Co and Fe; pyterpy=4′-(pyridin-4-yl)-2,2′:6′,2"-terpyridine) in ionic liquid.
FARADAY DISCUSSIONS, 193.
pp. 113-131.
Text
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Abstract
Extensive studies of various families of conjugated molecules in metal|molecule|metal junctions suggest that the mechanism of conductance is usually tunnelling for molecular lengths < ca. 4 nm, and that for longer molecules, coherence is lost as a hopping element becomes more significant. In this work we present evidence that, for a family of conjugated, redox-active metal complexes, hopping may be a significant factor for even the shortest molecule studied (ca. 1 nm between contact atoms). The length dependence of conductance for two series of such complexes which differ essentially in the number of conjugated 1,4-C<sub>6</sub>H<sub>4</sub>- rings in the structures has been studied, and it is found that the junction conductances vary linearly with molecular length, consistent with a hopping mechanism, whereas there is significant deviation from linearity in plots of log(conductance) vs. length that would be characteristic of tunnelling, and the slopes of the log(conductance)-length plots are much smaller than expected for an oligophenyl system. Moreover, the conductances of molecular junctions involving the redox-active molecules, [M(pyterpy)<sub>2</sub>]<sup>2+/3+</sup> (M = Co, Fe) have been studied as a function of electrochemical potential in ionic liquid electrolyte, and the conductance-overpotential relationship is found to fit well with the Kuznetsov-Ulstrup relationship, which is essentially a hopping description.
Item Type: | Article |
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Depositing User: | Symplectic Admin |
Date Deposited: | 06 Sep 2016 08:15 |
Last Modified: | 12 Oct 2023 11:05 |
DOI: | 10.1039/c6fd00080k |
Related URLs: | |
URI: | https://livrepository.liverpool.ac.uk/id/eprint/3003180 |