CrossRef Competing interests The authors declare that they have no competing interests. Authors’ contributions MO carried out the theoretical work in collaboration with KI. KY supplied experimental information. YM is the supervisor of the project. All authors read and approved the final manuscript.”
“Background Fundamental research regarding the quantum
transport mechanisms in individual molecules is of vital importance for molecular electronics. In the realization of a metal-molecule-metal junction, the Fermi energy BI 2536 supplier of the metal lies within a relatively large HOMO-LUMO gap (HOMO, highest occupied molecular orbital; LUMO, lowest unoccupied molecular orbital) and the electrons tunnel coherently across the molecular junction. In this description, the conductance of a single-molecule
decays exponentially as a function of its length, and this has been indeed confirmed for prototypical molecular backbones like non-conjugated alkane chains [1, 2] and π-conjugated molecular wires [3, 4]. However, such a simple tunneling picture does not take into account the effect of quantum interference that can strongly influence charge transport EX 527 research buy at the molecular scale [5, 6]. The understanding and control of quantum interference phenomena at the molecular scale may lead to single-molecule devices with new functionalities and, therefore, are a subject of increased scientific interest both theoretically [7–11] and experimentally [12–16]. An archetypal system, in which quantum interference LCZ696 mouse effects ASK1 are expected, is a single benzene ring . It has been shown theoretically that a benzene ring connected between two electrodes in a para configuration should have a conductance that is several orders of magnitude higher than that of a meta configuration [7, 17]. This reduction in the molecular conductance can be understood in terms of interference effects occurring between electron
waves propagating through different pathways. These pathways are separated in energy, and the interference between their transmission components can lead to constructive or destructive interference [7, 8, 18, 19]. Over the years, a large variety of techniques and methods have been employed to investigate the electronic properties of individual molecules connected between metallic electrodes. In particular, the advances obtained during the last decade using the break-junction technique  have revolutionized our understanding about charge transport through single-molecule junctions. This technique consists in repeatedly moving two metallic electrodes into and out of contact with each other in the presence of molecules equipped with suitable anchoring groups. During the separation of the electrodes, signatures of the formation of molecular junctions can be observed and statistical analysis permits to obtain the most probable conductance values for a single-molecule junction.