Evidence for a hopping mechanism in metal| single molecule| metal junctions involving conjugated metal-terpyridyl complexes; potential-dependent conductances of complexes [M(pyterpy)2]2+ (M = Co and Fe; pyterpy=4′-(pyridin-4-yl)-2,2′:6′,2"-terpyridine) in ionic liquid

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)2]2+ (M = Co and Fe; pyterpy=4′-(pyridin-4-yl)-2,2′:6′,2"-terpyridine) in ionic liquid. FARADAY DISCUSSIONS, 193. pp. 113-131.

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Official URL: http://dx.doi.org/10.1039/c6fd00080k

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-C6H4- 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)2]2+/3+ (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
Depositing User:	Symplectic Admin
Date Deposited:	06 Sep 2016 08:15
Last Modified:	12 Oct 2023 11:05
DOI:	10.1039/c6fd00080k
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3003180