title: Long-range electron tunnelling in oligo-porphyrin molecular wires.
abstract: Short chains of porphyrin molecules can mediate electron transport over distances as long as 5-10 nm with low attenuation. This means that porphyrin-based molecular wires could be useful in nanoelectronic and photovoltaic devices, but the mechanisms responsible for charge transport in single oligo-porphyrin wires have not yet been established. Here, based on electrical measurements of single-molecule junctions, we show that the conductance of the oligo-porphyrin wires has a strong dependence on temperature, and a weak dependence on the length of the wire. Although it is widely accepted that such behaviour is a signature of a thermally assisted incoherent (hopping) mechanism, density functional theory calculations and an accompanying analytical model strongly suggest that the observed temperature and length dependence is consistent with phase-coherent tunnelling through the whole molecular junction.
authors.affiliation: Chemistry Department, University of Liverpool, Liverpool L69 7ZD, UK.
authors.forename: Gita
authors.initials: G
authors.lastname: Sedghi
authors.forename: Víctor M
authors.initials: VM
authors.lastname: García-Suárez
authors.forename: Louisa J
authors.initials: LJ
authors.lastname: Esdaile
authors.forename: Harry L
authors.initials: HL
authors.lastname: Anderson
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Lambert
authors.forename: Santiago
authors.initials: S
authors.lastname: Martín
authors.forename: Donald
authors.initials: D
authors.lastname: Bethell
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Higgins
authors.forename: Martin
authors.initials: M
authors.lastname: Elliott
authors.forename: Neil
authors.initials: N
authors.lastname: Bennett
authors.forename: J Emyr
authors.initials: JE
authors.lastname: Macdonald
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Nichols
mesh_terms: D004553:Electric Conductivity; D004579:Electron Transport; D008956:Models, Chemical; D008958:Models, Molecular; D036103:Nanotechnology / Q000379:methods*; D053770:Nanowires / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013696:Temperature
chemical_list: D011166:Porphyrins